canister purge valve??

I believe I asked this before but what in the world is the canister purge valve? Is that the thing that looks like a coffee can under my hood? Could someone tell me its function and why I would need to replace it? It comes up when I had my codes read. Thanks!

yo Rigs!

You have a 96, right? and a 5.0?.. you really need to add that info to your signature someday

FOLLOWING IS FROM FORD[/url]; FOR OBDII:

Non-enhanced evaporative systems use a Vapor Management Valve to control purge vapor.

The Vapor Management Valve output circuit is checked for opens and shorts internally in the PCM by monitoring the status of the duty-cycled output driver. When the output driver is fully energized, or de-energized, the feedback circuit voltage should respond high or low accordingly (P0443). The Vapor Management Valve is checked for

circuit continuity (P1444, P1445)

& more for OBD II codes, also, what was your Code?[/b]"...The most common code that will set with these systems is P0443, which has to do with the circuit of the vapor management valve. This code is caused by an electrical problem inside the valve, the wiring to it,[/b] or a bad PCM.

Here is a pic by AIRTEX via rockauto.com

or

http://www.rockauto.com/catalog/raframecat...c1106110k938043

check vac lines and connector/wiring/pigtail/corrosion within connector; broken/burnt wires....

miesk5 said:

yo Rigs!You have a 96, right? and a 5.0?.. you really need to add that info to your signature someday

canister purge solenoid hangs in its vacuum line on da.. passenger side of the engine and the canister on frame rail, ...its wiring could have been burned by exhaust manifold

FOLLOWING IS FROM FORD; FOR OBDII:

Non-enhanced evaporative systems use either a Canister Purge Solenoid or a Vapor Management Valve to

control purge vapor

The Canister Purge (CANP) solenoid output circuit is checked for opens and shorts internally in the PCM by

monitoring the status of the duty-cycled output driver. When the output driver is fully energized, or de-energized,

the feedback circuit voltage should respond high or low accordingly (P0443). The Purge Flow Sensor is check for

circuit continuity (P1444, P1445)

The CANP solenoid functional check uses a Purge Flow Sensor (PFS) to check for adequate purge flow. The PFS

voltage is checked when the solenoid valve is normally open (> 75%), then checked when the solenoid valve is

commanded closed (0%). Too low a difference between the voltages indicates inadequate canister purge flow or a

PFS malfunction (P1443).

& more for OBD II codes, so, what was your Code?"...The most common code that will set with these systems is P0443, which has to do with the circuit of the canister purge solenoid or vapor management valve. This code is caused by an electrical problem inside the solenoid, the wiring to it, or a bad PCM. The other common code is a P1443. This is due to the PCM not seeing enough flow through the purge flow sensor when the canister purge solenoid is energized or the IACV not needing to change enough when the VMV is energized..."

Source: by Bob M at asashop.org

Here is a pic by AIRTEX via rockauto.com

or

http://www.rockauto.com/catalog/raframecat...c1106110k938043

check vac lines and connector/wiring/pigtail/corrosion within connector; broken/burnt wires....

Click to expand...

I put that in my signature, thanks. I think I know what the canister is. I just don't know if that's whats wrong with it. Thanks. I'll take a look.

Hello,

I have a 1996 Ford Bronco Eddie Bauer with a 5.8L engine and it is generating a P0443 code and the check-engine light comes on after resetting and then driving for a few miles.

I have replaced the canister purge valve (http://www.partsamerica.com/product_images/img/nie/fs3138-1.jpg), the egr pressure feedback sensor (http://www.partsamerica.com/product_images/AAP/GPS/VF-VP/VP8.jpg), and the O2 sensor on the exhaust (http://www.partsamerica.com/product_images/img/bos/15717.jpg) to clear various codes.

But the P0443 is still there.

I have run what tests I can -- the connections are good, the voltage is good, there don't seem to be any short circuits.

I am out of ideas.

Can anyone offer any advice?

Thanks!

-Mike

yo

P0443

ok, since wiring & connectors are good....and misrouted or damaged

hoses

btw, I replaced the intake manifold (below Throttle Body) to valve hose vac) a month ago; had a vac leak..but no DTC..

A long shot; check your gas cap's gasket; mine was rock hard after 9 years; bought new @ Ford (other brands don't have da tether strap attached or available); had a DTC while on vacay...it was intermittent.. seemed to come on only after re-fueling on a 1600 mile trip. SomethAng hit my brain and I checked the gasket... did the replacement and - no DTCs.. a lucky thing

And, do you smell gas at cap area?..check the filler neck, or it's gasket for leak...

This problem seems to be a biggie for us w/just hand-held OBD II Code Readers or using the Self Test process by BroncoJoe...

Do you have this noise?

Hooting Noise, fuel vapor return tube reacting w/the vapor management valve TSB 96-5-17 for 96 Bronco & F Series

Source: by Ford via diesel-central.com (click OK button a few times on password window)

read thru this lengthy article

DTC P0443 Description & Tests; Finding (& fixing) EVAP system leaks; "...If you can't detect a leak at the moment, record the data, clear the DTC and talk to the customer. There are a number of reasons why the system might not appear to be leaking when you test. Sure, the gas cap might be bad or may have been left loose. The gas tank may be too full to run an accurate test. Some leaks seal up when the temperature increases. You may need to retest the vehicle when it's cold..." by Ludlow B at Hearst Business Publishing May 2002 via findarticles.com

some bullets are;

"...One aspect to consider when testing the EVAP system in a Ford vehicle is that the PCM has an output test that can be run with a scan tool to turn on all the solenoids and relays (except the fuel injectors). If you plan to use a scan tool to close the vent solenoid, you'll need to unplug the VMV to keep it from opening. ..

Ford does not have a similar test that can be run with a hand-held scan tool. (The World Diagnostic System [WDS] isn't in the hand-held category.) ...

-----

and the Ford test procedure;

"...DTC P0443: INSPECT EVAP CANISTER PURGE VALVE CIRCUIT FOR INTERMITTENT FAILURE

Continuous Memory Diagnostic Trouble Code (DTC) P0443 may indicate an EVAP canister purge valve circuit failure.

Possible causes:

Damaged EVAP canister purge valve.

EVAP CANISTER PURGE or VPWR circuit open.

Rerun KOEO, KOER Self-Tests and retrieve Continuous Memory DTCs.

Is DTC P0443 present in Continuous Memory Self-Test only?

Yes No

GO to HW41 . GO to HW1 .

HW41 CHECK EVAP CANISTER PURGE VALVE CIRCUIT INTERMITTENT OPEN OR SHORT

Install breakout box, leave PCM disconnected.

Measure resistance between PCM test pin 67 or PCM test pin 56 and PCM test pin 71, while performing the following:

Lightly tap on the EVAP canister purge valve and observe a resistance change.

Wiggle the EVAP canister purge valve connector and vehicle harness between the valve and the PCM, observe a resistance change.

Does the resistance reading change to below 30 ohms or above 90 ohms (vehicles with test pin 67) or above 38 ohms (vehicles with test pin 56)?

Yes No

ISOLATE fault and REPAIR as necessary. RESTORE vehicle. COMPLETE PCM Reset to clear DTCs. RERUN Quick Test . UNABLE to duplicate or identify fault at this time. GO to Pinpoint Test Step Z1 with the resistance readingsand list of Possible causes.

HW42 VERIFICATION OF EVAPORATIVE EMISSION SYSTEM REPAIR USING ROTUNDA EVAPORATIVE EMISSION SYSTEM LEAK TESTER

Plug or tape atmospheric vent cap on EVAP canister (if applicable).

Remove fuel filler cap at fuel filler pipe.

Install Rotunda Evaporative Emission System Leak Tester 134-00056 or equivalent including the nitrogen or argon gas supply and pressure regulator.

Disconnect and plug fuel vapor hose to PF sensor (or EVAP canister purge valve on Ranger) from intake manifold at the intake manifold vacuum source.

Pressurize the EVAP system at 6.74 kPa (27 in-H 2 O) with tester.

Observe tester installation leak self-test for two minutes and then the EVAP system leak test.

Listen for a vacuum leak noise and check for substantial fuel vapor odors at isolated areas in the EVAP system.

Does the pressure applied to the EVAP system hold?

Yes No

REMOVE plug and RECONNECT fuel vapor hose from PF sensor (or EVAP canister purge valve) at intake manifold vacuum source. REMOVE EVAP System Leak Tester. REINSTALL fuel filler cap. TIGHTEN cap only one eighth turn so that cap initially clicks by sound or touch. COMPLETE PCM Reset to clear DTCs. Access EVAPPDC PID on scan tool. DRIVE vehicle (including a steady accelerator speed over 80 km/h (50 mph) until EVAPPDC PID shows 75 percent duty cycle). Then maintain approximate speed until duty cycle reaches zero percent. After additional two minute drive, bring vehicle to an idle. RERUN Quick Test . VERIFY a symptom no longer exists. GO to HW43 .

HW43 CHECK LOCATION OF EVAPORATIVE EMISSION SYSTEM PRESSURE LEAK

Systematically isolate area of potential pressure leak.

Close off pressure to EVAP system.

Disconnect and plug fuel vapor hose from fuel tank at EVAP canister.

Apply controlled pressure at 6.74 kPa (27 in-H 2 O to the EVAP system with the leak tester.

If pressure now holds, GO to the Powertrain/Engine Group, Evaporative Emissions Section in the Workshop Manual for EVAP canister diagnosis.

If system presure cannot hold, close pressure supply to system.

Disconnect and plug fuel vapor hose from EVAP canister at EVAP canister purge valve.

Again, apply controlled pressure to the EVAP system.

Does the pressure hold?

Yes No

REMOVE plugs. RECONNECT fuel vapor hose at EVAP canister. RETURN to Pinpoint Test Step HW14 to check EVAP canister purge valve integrity on Ranger or Pinpoint Test Step HW18 to check EVAP canister purge valve integrity on Mustang. REMOVE EVAP System Leak Tester. REINSTALL fuel filler cap. COMPLETE PCM Reset to clear DTCs. Access EVAPPDC PID on scan tool. DRIVE vehicle (including a steady accelerator speed over 80 km/h (50 mph) until EVAPPDC PID shows 75 percent duty cycle). Then maintain approximate speed until duty cycle reaches zero percent. After additional two minute drive, bring vehicle to an idle. RERUN Quick Test . VERIFY a symptom no longer exists. REMOVE plugs. CHECK for fuel vapor hose cracks or fuel vapor valve damage. EXAMINE and SECURE fuel vapor hose connections to components. REPAIR or REPLACE as necessary. REMOVE EVAP System Leak Tester. REINSTALL fuel filler cap. COMPLETE PCM Reset to clear DTCs. Access EVAPPDC PID on scan tool. DRIVE vehicle (including a steady accelerator speed over 80 km/h (50 mph) until EVAPPDC PID shows 75 percent duty cycle). Then maintain approximate speed until duty cycle reaches zero percent. After additional two minute drive, bring vehicle to an idle. RERUN Quick Test . VERIFY a symptom no longer exists.

Sorry, this one is a tough nut to crack w/out the Ford Tester and possibly a Smoke Machine.

Thank you for your quick response!

I do not have the hooting.

A lot of the procedures are things I can't do because I don't have the equipment, but I have read through all or most of it.

I have taken the Bronco to a Ford dealer, who grudgingly agreed to troubleshoot the problem tomorrow or the next day. Unfortunately, they're the only reasonably honest Ford dealer in my area, or at least the only one I would trust.

My only other option to get the truck stickered is to get an emissions inspection waiver, which in my state requires you to have spent $150 towards emissions-related repairs (I've exceeded this by far already), and this Ford dealer is authorized by the state to handle emissions waivers, but they are balking at the idea of doing this. I'm not quite sure why. Perhaps doing a waiver puts a pox on the dealership.

We'll see what they say on Wednesday. Maybe they'll have better luck diagnosing the P0443. If they tell me to replace the PCM, I'm going to pull the truck and take it someplace else. I really don't think the computer is to blame, or I'd be seeing other weird codes, and I haven't been. And there really does not appear to be a voltage problem to the purge valve, so why the code is being thrown is really a mystery.

yw,

I forgot to add my usual caveat about NOT replacing the PCM; good that you discount this too.

btw the gas cap code I mentioned in my 96 was P0440; it has some cause = to da P0443

With a P0440 OBD-II trouble code, diagnosis can be tricky at times. Here are some things to try:

Remove and reinstall the gas cap, clear the code, and drive for a day and see if the codes come back.

Inspect the EVAP system for cuts/holes in tubes/hoses

Inspect for damaged or disconnected hoses around the Evap purge solenoid

Check and/or replace the sensor

Check and/or replace the purge valve

Have a professional use a smoke machine to detect leaks

-----

Yes, we don't have the other test equipt avail @ a dealership for this one. That waiver sounds real good to me. Hard enuf finding good, guaranteed parts for some sytems now such as a VSS controller or the hydr unit for our 4WABS sys.

GL!

mishspring said:

Thank you for your quick response!
I do not have the hooting.

A lot of the procedures are things I can't do because I don't have the equipment, but I have read through all or most of it.

I have taken the Bronco to a Ford dealer, who grudgingly agreed to troubleshoot the problem tomorrow or the next day. Unfortunately, they're the only reasonably honest Ford dealer in my area, or at least the only one I would trust.

My only other option to get the truck stickered is to get an emissions inspection waiver, which in my state requires you to have spent $150 towards emissions-related repairs (I've exceeded this by far already), and this Ford dealer is authorized by the state to handle emissions waivers, but they are balking at the idea of doing this. I'm not quite sure why. Perhaps doing a waiver puts a pox on the dealership.

We'll see what they say on Wednesday. Maybe they'll have better luck diagnosing the P0443. If they tell me to replace the PCM, I'm going to pull the truck and take it someplace else. I really don't think the computer is to blame, or I'd be seeing other weird codes, and I haven't been. And there really does not appear to be a voltage problem to the purge valve, so why the code is being thrown is really a mystery.

Click to expand...

Well, the Ford dealer ran all the tests "by the book" and they showed unconventional voltage coming out of the PCM. They verified that the wiring and wiring harnesses are not to blame, and they are now completely convinced that the PCM itself is to blame.

The code won't go away, and the truck fails emissions inspection.

Any recommendations? Rebuild my PCM with www.fordecu.com or get an after-market one from partsamerica.com?

Thanks!

yo!

Sorry to hear it's da PCM.... it's the always the last thAng to fail...did you have to jump or charge your batty recently? Or have water on or under carpet on driver's side after a heavy rain or car wash?

also; "...PCMs typically fail for one of two reasons: voltage overloads (often due to a short in a solenoid or actuator circuit) or environmental factors (corrosion, thermal stress or vibration). If the shorted solenoid or actuator is not found and repaired, the voltage overload it creates may damage the replacement PCM, too

As for environmental factors, water is the main thing to avoid. If water gets inside a PCM, it can short circuits and set up irreversible corrosion that ruins electronic connections..."

Anyway; that is a stiff $ from fordecu..- unless you go for their R&R service.

Cardone is a ok for many items..

There are 4 major PCM rebuilders in the United States {Borg Warner - Cardone - Micro-Tech - Standard)

Option is to go for a yard PCM.. no guarantees there - I use this yard search

http://www.mypartshop.com/default.aspx

select All Parts

GL!

The battery was replaced with a new one a few years ago. The truck sat for a few weeks a month or two ago and had to be trickle-charged before it would start. I guessed there is some sort of parasitic draw on it somewhere, maybe the after-market radio. Why do you ask about the battery?

I guess I will go with the Cardone remanufactured one from Advance Auto Parts / partsamerca.com, as I can't see spending extra to have my specific one rebuilt by who-knows-who, and I don't want to go junkyard hopping, hoping for a match or to get lucky.

There was no water to my knowedge.

On the topic of solenoids, though, I was looking on Cardone's web site and they suggested that a very often overlooked culprit in PCM failure is the TCC (torque converter clutch) solenoid. I did have my transmission professionally rebuilt a year and a half ago, but I have no idea whether they replaced the TCC or not. I guess we'll find out if I blow another PCM. I kinda doubt that's related though.

But I did recently replace the EGR solenoid, to clear another code that was showing up. Do you think that solenoid went so bad that it fried the PCM???

So...I don't really know anything about PCMs...I just get the one with the right calibration code on it, stick it in, and presto magic-o, it's just going to work? No reprogramming, no popping a PROM chip out of one PCM into the other, nothing complicated like that?

Thanks again!

yo!

OK, here are replies below each of your Qs;

The battery was replaced with a new one a few years ago. The truck sat for a few weeks a month or two ago and had to be trickle-charged before it would start. I guessed there is some sort of parasitic draw on it somewhere, maybe the after-market radio. Why do you ask about the battery?

& There was no water to my knowedge.

& On the topic of solenoids, though, I was looking on Cardone's web site and they suggested that a very often overlooked culprit in PCM failure is the TCC (torque converter clutch) solenoid. I did have my transmission professionally rebuilt a year and a half ago, but I have no idea whether they replaced the TCC or not. I guess we'll find out if I blow another PCM. I kinda doubt that's related though.

& But I did recently replace the EGR solenoid, to clear another code that was showing up. Do you think that solenoid went so bad that it fried the PCM???

* Read this by AutoTap;

"...WHY DID IT DIE?

One way to reduce the risk of PCM warranty problems is to find out why the old PCM died. Determining the cause of death may not always be possible, but it may be essential to prevent the same thing from damaging the replacement PCM in some cases.

PCMs typically fail for one of two reasons: voltage overloads (often due to a short in a solenoid or actuator circuit) or environmental factors (corrosion, thermal stress or vibration). If the shorted solenoid or actuator isn't found and repaired, the voltage overload it creates may damage the replacement PCM, too.

As for environmental factors, water is the main thing to avoid. If water gets inside a PCM, it can short circuits and set up irreversible corrosion that ruins electronic connections. Most remanufacturers won't even attempt to repair a PCM if the vehicle it came out of was submerged in a flood. Replacement is the only option. Thermal stress and vibration can form microcracks in circuit boards (which are repairable). This often has more to due with the ruggedness of the circuit design than operation factors in the vehicle itself..."

---------------

I guess I will go with the Cardone remanufactured one from Advance Auto Parts / partsamerca.com, as I can't see spending extra to have my specific one rebuilt by who-knows-who, and I don't want to go junkyard hopping, hoping for a match or to get lucky.

* I capice; I went thru 2 yard 4WABS Controllers (computers) at yards and both of those are bad too..

----------------------------------

So...I don't really know anything about PCMs...I just get the one with the right calibration code on it, stick it in, and presto magic-o, it's just going to work? No reprogramming, no popping a PROM chip out of one PCM into the other, nothing complicated like that?

* Powertrain Control Module Location, Bronco; 1987-1996 behind drivers side kick panel

Read this;

Powertrain Control Module Location & Removal Instructions, Ford Source: by Westers Garage westersgarage.eidnet.org

* READ this from same source;

"...REPLACEMENT TIPS

Replacing a PCM is essentially a matter of swapping boxes. Accessibility can be a problem on some vehicles because the PCM is often buried under or behind other components in the instrument panel, climate control system or console. Some are located under a seat and require removing the seat.

Regardless of the PCM's location, though, one thing every installer should do (but many don't) prior to removing the old PCM and installing the replacement PCM is disconnect the battery.

Once the PCM has been installed and reconnected, the battery can be reconnected, too. But the job isn't done yet. Many PCMs have to undergo a "relearning" procedure after they've been installed or if they've been disconnected from the battery.

See your Owners Manual for this re-learning; it is same as when batty is disconnected...

Adaptive Strategy Relearn Procedure: After repairs have been made and the KAM cleared drive the vehicle for at least ten miles to allow the PCM to relearn the values for optimum performance. Note: During the ten mile relearn drive, the vehicle may exhibit some driveability symptoms. These should be eliminated when the KAM has relearned the operating values. Source: by Ford via miesk5 (Al M) at Ford Bronco Zone Forums

Also, ensure you have no STATIC on your fingers when you handle the PCM// can get it from a dry carpet..etc..

-------

I just get the one with the right calibration code on it, stick it in, and presto magic-o, it's just going to work? No reprogramming, no popping a PROM chip out of one PCM into the other, nothing complicated like that?

@ []Right! No other things needed; just double & triple CK that CAL CODE...---------

GL!

wow Im glad I don't have an electronically controlled engine, need a freakin electrical engineering degree. i'll stick to my carbs and bad gas mileage

The Cardone PCM arrived and I put it in last night. You could tell the new computer was better than the old one right away: it idled great right from the get-go, the fuel pump didn't run constantly, the check-engine light stayed off, no more P0443 code, and it just ran better overall. But the overdrive (OD) light started flashing as soon as I turned the car on, and stayed flashing the whole time. I drove it for maybe 25 miles. I have an OBD reader but there are no codes for it to read, with a flashing overdrive light.

I'm going to take it back to the place that rebuilt the transmission last year. If they rebuilt the trans but did not replace the pressure control solenoid or TCC, shame on them. I can't think of any other reason why the OD light would be blinking???

Unless I need to drive it longer in "limp" mode for the computer to learn the car? I have no idea, as this is the first PCM I've ever replaced.

yo!

GREAT!

Is the tranny shifitng ok?

If ok, then look @ this; it will make ya happy!

Transmission Control Indicator Lamp (TCIL) Malfunction due to a faulty O/D cancel LED Part #F58Z-7G550-A Source: by ATC-Distribution Group Inc. atcdg.com via web.archive.org

Transmission Control Indicator Lamp (TCIL) & Switch/Cap Installation in 92-96

Source: by miesk5 (Al M)

"...E4OD Overdrive Cancel Light & Switch Replacement; It is easy to replace & under $17.00 from local Ford dealer or THE BRONCOZONE Sponsor; Jeff's; be ready to catch the switch/LED assy when prying it off; it is spring loaded..not much force..."

Source: by miesk5 (Al M)

and; I need to look for my notes on what fuse blew due to a harness short under strg column that affected the OD Cancel Light (it blinked randomly, no Trouble Codes or tranny malfunctions though); think it was 6 or 7

or some other rel <$ probs (MLPS, etc.); many are listed in my site.. but since NO CODES!~!!!!

Transmission Control Indicator Lamp (TCIL) Button, LED & Cap (replacement part) by broncograveyard.com

"...Item #37018 - New

1992-96 Ford Bronco 1992-96 Ford Truck

This is the overdrive button on the end of the column shifter, comes with small cap.

Our Price: $10.00 ..."

---------------

mishspring said:

The Cardone PCM arrived and I put it in last night. You could tell the new computer was better than the old one right away: it idled great right from the get-go, the fuel pump didn't run constantly, the check-engine light stayed off, no more P0443 code, and it just ran better overall. But the overdrive (OD) light started flashing as soon as I turned the car on, and stayed flashing the whole time. I drove it for maybe 25 miles. I have an OBD reader but there are no codes for it to read, with a flashing overdrive light. GREAT! /emoticons/[email protected] 2x" width="20" height="20" /> I'm going to take it back to the place that rebuilt the transmission last year. If they rebuilt the trans but did not replace the pressure control solenoid or TCC, shame on them. I can't think of any other reason why the OD light would be blinking???
Unless I need to drive it longer in "limp" mode for the computer to learn the car? I have no idea, as this is the first PCM I've ever replaced.

Click to expand...

also; fyi and for da record here...

"..."Limp Mode" or "Fail Code" Condition

"Fail Code" conditions or "Limp Mode" happens when the vehicle computer recognizes a problem in it's logic. When an expected signal value from a sensor is sent to the computer and is not within the computer's programmed specifications, "secondary" programs are activated by the computer to strive to protect the transmission from damage the improper sensor signal might cause to occur.

In other words, the computer is always expecting certain signal values from certain sensors i.e. the temperature sensor, the speed sensor, the throttle position sensor, etc. As long as these signals are what it would normally expect for the conditions and is normal based on all the other signals it is receiving from other sensors, it acts normally and accordingly.

If the computer, all of a sudden, receives some crazy signal from one of the sensors that is out of the normal range expected from this sensor, it will go to "emergency" or "secondary" measures.

These emergency measures vary depending on the severity of the defective signal. All this is preprogrammed into the computer's logic by the manufacturer. The manufacturer has decided that as long as a certain parameter of a particular signal is sent from a sensor to the computer, all is well. The manufacturer decided that if this signal is higher than their highest parameter or lower than their lowest parameter, something is wrong with that sensor and the computer should make someone aware of the situation and take action to try to "save" the vehicle systems or powertrain.

Perhaps the computer will simply cause the "check engine" light to come on. The signal variation wasn't severe or critical to cause any mechanical failures but the vehicle's operator is made aware that he or she should have the vehicle checked out electronically to see if a minor sensor has broken down or is starting to send the odd irratic signal. This type of condition is commonly referred to as a "soft code". Normal functions are not affected but if the repair is not made, performance or fuel efficiencies might suffer. Perhaps the sensor only malfunctioned one time and all other times was fine. This might be an early warning of a sensor that is beginning to fail or has a loose connector or connection.

Other times the signal needed to perform operations normally is so far out of specification that the computer has no choice but to go into survival mode. With transmissions, the computer will cause the internal tranny fluid line pressure to default to high to protect clutches and bands. The transmission also turns off the shift solenoids to cause the unit to default to a single gear, usually second or third. All normal instructions to control line pressure are overridden so a hazardous "slipping condition" cannot occur easily. This theoretically is so that the vehicle's driver can get the damaged vehicle to the next town for repairs. This condition is commonly called "Limp Mode" for this reason. You limp to the next town in second or third gear only, at full line pressure so the tranny guts won't slip on your trip in.

By the way, interestingly and just as a side note, if the cable harness going to your transmission was ever to become detached, severed or damaged, your transmission would also go to "limp mode".

The vehicle's computer would immediately sense that it has lost contact with the transmission and would set the codes and send "limp mode" signals to the tranny. But because the harness is severed between the computer and the transmission, no computer signals will reach the transmission. These sent signals, however, would have had the identical affect on the transmission as what taking away supplied power to the shift and line pressure solenoids has as in the case of a transmission harness being detached or cut. Due to the engineered voltage strategies of the solenoids, the transmission simply defaults to a single gear and line pressure defaults to high, all in order to "limp" you home.

A Throttle Position Sensor that improperly sends a reading that it is wide open when in fact it is physically closed would be detected by the computer when it compared this reading with the vehicle speed sensor that perhaps is showing very slow vehicle speed. The signal, by itself can't be considered wrong but when put against all the other sensor signals of the system might cause a computer concern. The computer, at this point, unable to "trust" the collection of signals because together they are not making sense in it's logic, will simply go to limp mode in the transmission to protect it and make the operator aware that something is wrong with one of the sensors and a mechanic's attention is needed to correct the situation.

This Fail Code Condition will show up as a "code" reading on a mechanic's scanner. This code will be cross referenced to a table from the manufacturer and represent a problem with a particular sensor or a group of sensors or system. It gives the mechanic a better idea of where the problem has showed up and which systems or sensors are involved in the malfunction. The table of codes and what each one means, is commonly programmed right into the scanner tool that the mechanic uses for easy reference.

i.e. the scanner tool might tell the mechanic that the computer has thrown a code "35" which is the "transmission fluid temperature sensor" and might give the mechanic the recommended values this sensor should provide and what it in fact provided...

In your electronic transmission, many important functions are controlled by the computer. Shift timing, sequence, feel, line pressure are controlled. The information from the vehicle speed sensor affects fuel injection, fuel mixture, ABS, transmission operation, etc. Load information of your engine is commonly taken primarily from the TPS (throttle position sensor) or the MAP sensor (manifold absolute pressure). This controls transmission shifting and downshifting when stepping on the gas or climbing hills. A regular scanning of the computer for any set "hard" or "soft" codes is something routinely done by most good tuneup shops these days.

Greg O - AutoTrans Inc...."

so since it is shifting GREAT & NO CODES on Scanner for both KOEO & KOER...(assuming KOER test was done with engine at Normal OPerating Temperature).... suspect the bad TCIL LED/switch or wiring short...etc.

one more..promis I'll stop..

"Relearning" by Ford,,, (in your Owner's Guide, page 63)

Because your vehicle

miesk5 said:

one more..promis I'll stop..

Click to expand...

Actually, please don't feel like you have to stop -- I am finding all of this incredibly useful and valuable, and I am very grateful.

Unfortunately, in this case the flashing of the OD light is rhythmic and steady, and I don't think it's a malfunction in the stem itself, as described in the bulletin that you referenced.

The transmission itself shifts fine, though, and feels like it has more than one or two gears, so I don't think that it's in "limp" mode, based on your description.

So - steady blinking light, but doesn't feel like limp mode, and no codes showing up in my Actron CP9180, but I don't think I can tune in to transmission codes with that device.

Keep writing if you have the time. I do appreciate it. Thank you!

ok,

Did you do the KOER test after the KOEO and after the engine reached Normal Operating Temperature?

Next; Does your Cp9180 go thru the "Vehicle Selection" phase completely?

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It should show tranny codes esp. since the TCIL is blinking.

Some OBD II/E4OD DTCs you would see are;

P0117 - Torque converter clutch will always be off, resulting in reduced fuel economy

P0122 P0123 P1120 - Harsh engagements, firm shift feel, abnormal shift schedule, torque converter clutch does not engage, torque converter clutch cycling.

P0741 - TCC slippage/erratic or no torque converter clutch operation. Flashing Transmission Control Indicator Lamp (TCIL).

btw, I have the Actron CP9135 AutoScanner Diagnostic Code Scanner with On Screen Definitions - got it as a gift; it works as advertised and is ok for my use, but the instructions ****: they don't mention warming eng up for KOER test and a few other thAngs, such as providing very limited Code Definitions; I called em and mentioned this omission; tech support said "OK" and hung up. And it doesn't read the 4WABS Codes.

Did you check fuses?