[bergs]

My 1996 bronco throws the following codes:

p0135
p0136
p0141
p0155
p0174

I know that they are for the 02 sensors and a lean condition. Whats your experience on tracking down these codes and keeping them from coming back.

[BroncoJoe19]

When it comes to codes... Miesk5 is the master.

Here is the thread that pertained to my O2 sensor experience with my '98 windstar.
http://broncozone.co...&...ost&p=76967

[BroncoJoe19]

Here is a thread similar to your's
http://www.obd-codes....php?f=1&t=2667
IF you would like more specific help, please post what the English version is for each of the numbered codes.

[miesk5]

yo!
thnx Joe!

Bergs, LOOK HERE

Before replacing O2 sensors, ck for an exhaust leak; Vacuum Leaks; intake leak after MAF sensor

[bergs]

thanks guys for your speedy replies. Theres a bunch of boogered up wiring on this truck. it had some kind of air horns mounted underneath it, whacky foglight(piaa) wiring under the hood, and some stereo wiring. I havent had a chance to even look at the truck too much. but i think its some of the wiring that previous owners did. I just got the truck. Which fuses should I check first. I noticed that there was a yellow wire coming out of the fuse box that is on the drivers side inner fender fuse box. the wire is cut and just hanging there. I didnt open it, but i figure its more of the old owners horrific wiring. i know the muffler is rusted out, i'll check the exhaust up by the cats and sensors for leaks too. I have a feeling that its butchered wiring, or deteriorated wiring, or a fuse.

[miesk5]

yo, yw
Yellow Wire... be wary of that one; I don't have good www connectivity here right now, but your Air Bag may be involved.

Wiring ia a mess. Suggest buying a FORD EVTM/PCED Service Manual CD on e bay to go thru the wiring and prob vacuum lines, etc. No one fuse for the sensors; just look at the sensors' connectors, & wires for corrosion or cuts..etc.
More on O2 sensors for you Berg;

Regardless of how the engine is mounted in the vehicle, conventional or transverse, the HO2S naming convention stays the same in relationship to engine banks 1 and 2. Bank 1 will always be the bank containing the #1 cylinder. See Fig. 1 in TSB 01-9-7
DRIVEABILITY - HO2S (HEATED OXYGEN SENSOR), CATALYST, AND FUEL SYSTEM MONITORS - SERVICE TIPS - OBD II VEHICLES ONLY - 96 Bronco, TSB 01-9-7
Source: by Ford via v8sho.com
Testing, Bronco & Ford - There may be three wires on the O2 sensor; two gray wires and one black. The black should read ground. One gray wire should read 12V with the ignition on, and the other gray wire is the one we are after. Probe this wire with the engine warm, and running with a voltmeter’s (+) probe, and ground the negative probe. While the vehicle is running, the reading should be approximately 0.5V. A reading below this indicates a lean air fuel mixture; a reading above this indicates a rich mixture. If no reading is present, and all connections are good, the sensor is probably in need of replacement
Source: by broncoii.org

DTC 41, 42, 91, 92, 136, 137,139, 144, 171, 172, 175, 176, 177 & some Possible Causes for Rich & Lean HEGO The engine temperature must be greater than 50°F (10°C) to pass the KOEO Self-Test and greater than 180°F (82°C) to pass the KOER Self-Test. To accomplish this, the engine should be at normal operating temperature
Source: by Ryan

When diagnosing a vehicle with a MIL On and DTC(s) P0171, P0172, P0174, and/or P0175 in continuous memory, do not replace the downstream HO2S sensors. These DTCs have no connection to the downstream HO2S sensor function nor its diagnosis for faults. Always verify the vehicle concern, then perform the pinpoint diagnostics from the appropriate PC/ED Service Manual.

[bergs]

i was cleaning up the wiring and noticed that there are a bunch of old connectors for old accesories going to the starter solenoid. the post that they go to has been extended with a bolt/nut combo to allow several round type connectors to fit on it. I cant get the bolt off to allow me to remove the connectors. also the stud that i am talking about wobbles and is loose. could this be the source of a bad ground causing the p0135, etc.? i think i may put in a new solenoid, your thoughts?

also i found a leak in the intake piping, the hose clamps on the throttle body hoses were totally loose. i tightened them up. so far no more lean condition code has come back.

[bergs]

i cleaned up all the wiring, and cant find any vacume leaks underhood. there is one in the dash board, the A/C only blows out of the defroster vents. I can hear the vacume hiss in there. could that be a reason? I think that there must be a problem with the wiring. Where is the PCM? i checked the wires on the sensors themselves and they look ok to me. at this point i wish i could just replace the H02S's and be done with it, but i think its some wiring issue. at this point its only throwing P0135, P0141, and P0155.

[BroncoJoe19]

bergs, on Jul 23 2008, 05:00 PM, said:

i cleaned up all the wiring, and cant find any vacume leaks underhood. there is one in the dash board, the A/C only blows out of the defroster vents. I can hear the vacume hiss in there. could that be a reason? I think that there must be a problem with the wiring. Where is the PCM? i checked the wires on the sensors themselves and they look ok to me. at this point i wish i could just replace the H02S's and be done with it, but i think its some wiring issue. at this point its only throwing P0135, P0141, and P0155.

With that vacuum leak, it is letting air into the system which could allow one of the sensors to read a lean mixture.
A prerequisite to properly pulling codes is to check and correct vacuum leaks.

Hopefully it will be an easy one to get at.
joe

[BroncoJoe19]

: P0135 - HO2S Sensor : During testing the : * Short to VPWR in : - wiring. :
: Circuit Malfunction : HO2S Heaters are : harness or HO2S. : - Damaged HO2S :
: (HO2S-11) : checked for opens : * Water in harness : heater. :
: : /shorts and excessive : connector. : - Damaged PCM. :
: : current draw. The test : * Open VPWR circuit. :
: : fails when current : * Open GND circuit. :
: : draw exceeds a : * Low battery :
: : calibrated limit and : voltage. :
: : /or an open or short : * Corrosion or poor :
: : is detected. : mating terminals :
: : : and wiring :
: : : * Damaged HO2S :
: : : heater. :
: : : * Damaged PCM. :
.
Here is a list of grounds for a '92 - '96 bronc

I took a look in my Haynes manual.
They list 10 separate grounds... A-J.

A. Starter mounting bolt
B. Right front of Engine compartment near the battery
C. Lower left front of engine
D. Right front of engine compartment on upper radiator support.
E. Left front of engine compartment Upper radiator support
F. Bottom of cowl panel
G. Rear of left fender apron
H. Behind bottom of right cowl panel
I. Left rear corner of cargo area near rear lamp assembly
J. Under center rear of vehicle on rear cross member.

Take a look at the wiring diagram in your manual to see which of the listed grounds goes to the PCM, and check that one. Also Take a look at C that should be the ground for the O2 sensors.

[bergs]

BroncoJoe19, on Jul 23 2008, 06:34 PM, said:

: P0135 - HO2S Sensor : During testing the : * Short to VPWR in : - wiring. :
: Circuit Malfunction : HO2S Heaters are : harness or HO2S. : - Damaged HO2S :
: (HO2S-11) : checked for opens : * Water in harness : heater. :
: : /shorts and excessive : connector. : - Damaged PCM. :
: : current draw. The test : * Open VPWR circuit. :
: : fails when current : * Open GND circuit. :
: : draw exceeds a : * Low battery :
: : calibrated limit and : voltage. :
: : /or an open or short : * Corrosion or poor :
: : is detected. : mating terminals :
: : : and wiring :
: : : * Damaged HO2S :
: : : heater. :
: : : * Damaged PCM. :
.
Here is a list of grounds for a '92 - '96 bronc

I took a look in my Haynes manual.
They list 10 separate grounds... A-J.

A. Starter mounting bolt
B. Right front of Engine compartment near the battery
C. Lower left front of engine
D. Right front of engine compartment on upper radiator support.
E. Left front of engine compartment Upper radiator support
F. Bottom of cowl panel
G. Rear of left fender apron
H. Behind bottom of right cowl panel
I. Left rear corner of cargo area near rear lamp assembly
J. Under center rear of vehicle on rear cross member.

Take a look at the wiring diagram in your manual to see which of the listed grounds goes to the PCM, and check that one. Also Take a look at C that should be the ground for the O2 sensors.

Thanks Joe! at least i have some direction now. I'm gonna pick up a haynes manual for sure. I dont have a wiring diagram, do you think you could look and see which ground is for the pcm. I'm sorry to be a pain, I really appreciate your help.

[michibronc]

Hey Bergs,

Try this link. It talks about a dirty MAF causing the lean code. There's also a lot of info on Miesk5's website at broncolinks.com. It's got an absolute wealth of info. I cruise it often!

good luck - I'm working through the same issues currently! Haven't had much time to play with it yet.

[bergs]

i'm looking for a ground at "the lower left front of engine" and i cant find one. all i see the the negative battery cable that attaches to the block on the lower passenger side. I cant tell where the o2 wires go. i can see that the passenger front sensor goes into a wiring loom that goes up to the starter solenoid (i think), but thats it? i have a digital volt meter but i dont know what setting to put it on, or how to use it at all. where do i stick the red and black prongs? any advise is much appreciated

[BroncoJoe19]

Looks like B G and E are important grounds.
Also it appears that the orientation of left and right is that Right is the passenger side.

I don't have my truck here to take a look at it, (mine is a '90 anyway)
If you have a good ground to the block, it doesn't matter.. left or right.

[miesk5]

yo,
awhile ago, I went thru my 1996 Ford Electrical & Vacuum Troubleshooting Manual (EVTM), Service, etc. Tech publication CD and saved this on Grounds:
10-2 Grounds
LH front of engine compartment, on upper radiator support (F7) G100


G101 RH front of engine compartment, front of fender apron (D1) - RH = Passenger side mine has 2 small black wirres near starter relay

G103 (battery to engine) Lower RH front of engine (C1)
Component
4WABS Pump Motor
Battery
Data Link Connector (DLC)
Mass Air Flow (MAF) Sensor
Powertrain Control Module (PCM), 5.0L
Powertrain Control Module (PCM), 5.8L
Right Front Park/Turn Lamp
Right Front Side Marker Lamp
Right Headlamp

G104 Rear of LH fender apron (A9)

G200 Behind bottom of RH cowl panel (F7)

G201 Behind bottom of LH cowl panel (E1)

G400 Rear Window Defroster 56-1
LH rear corner of cargo area, near rear lamp assembly (F8)

G401 Trailer/Camper Adapter 95-3
LH rear corner of cargo area, near rear lamp assembly (F9)

10-3 Grounds
Component
A/C Clutch Diode
A/C Clutch Field Coil
Fuel Pump Module SPLICED Rear lamps harness, near T/O to fuel pump module
Left Backup Lamp
Left License Lamp
Left Rear Park/Stop/Turn Lamp
Right Backup Lamp
Right License Lamp
Right Rear Park/Stop/Turn Lamp
Transmission Range (TR) Sensor, with 4R70W Transmission
Transmission Range (TR) Sensor, with E4OD Transmission

Lower RH front of engine (C1)

Grounds 10-5
Behind bottom of RH cowl panel (F7)
Component
Air Bag Diagnostic Monitor
Electronic Shift Control Module
Instrument Cluster
Programmable Speedometer/Odometer Module (PSOM)
Remote/Keyless Entry Module
Speed Control Servo/Amplifier Assembly

Grounds 10-6
Behind bottom of LH cowl panel (E1)
Component
Compass/Outside Temperature Module
Day/Night Mirror
Inside Cargo Lamp
Left Power Lumbar Compressor Motor
Outside Cargo/High Mount Stop Lamps
Right Power Lumbar Compressor Motor
Seat Belt Switch

G100 & G104 (tied together in diagram) Grounds 10-11
LH front of engine compartment, on upper radiator support (F7)

Grounds 10-11
Rear of LH fender apron (A9)

Grounds 10-11
Rear of LH fender apron (A9)
Component
4WABS Control Module
4WABS Data Link Connector
4WABS Relay #1
Instrument Cluster
Powertrain Control Module (PCM), 5.0L
Powertrain Control Module (PCM), 5.8L
Programmable Speedometer/Odometer Module (PSOM)
Trailer Relay Box

G100 LH front of engine compartment, on upper radiator support (F7)
Component
Fuel Pump Module
Inertia Fuel Shutoff
Misfire Sensor
Misfire Sensor Shield
Output Shaft Speed (OSS) Sensor
Powertrain Control Module (PCM), 5.0L

Grounds 10-6
Behind bottom of LH cowl panel (E1)

as you can see, some are repetitive because I haven't lined all these up yet. And the CD didn't show the battery ground yet... still need to look at it again when things slow down here.
I think I need a full session on the PC to coordinate all grounds to individual components, as well as linking them to every connector.
& on my 96, the RH Engine Ground also branches to RH firewall near heater box & down to frame

This post has been edited by miesk5: 25 July 2008 - 08:37 AM

[bergs]

I'm going to clean up the grounds that i can find and see what that does. Can someone give me a quick run down of the procedure of testing the o2 sensors with the digital multi meter. i have the meter but i dont know where to probe or if the truck should be running or anything. if i could actually test the wiring i'd be in better shape. Thanks for all your replies so far. you guys have been a big help.

[miesk5]

bergs, on Jul 25 2008, 06:29 AM, said:

I'm going to clean up the grounds that i can find and see what that does. Can someone give me a quick run down of the procedure of testing the o2 sensors with the digital multi meter. i have the meter but i dont know where to probe or if the truck should be running or anything. if i could actually test the wiring i'd be in better shape. Thanks for all your replies so far. you guys have been a big help.

bergs, take a look @ one of replies aboce on teesting the O2 sensors; see if thay have the 3 wire leads.

Testing, Bronco & Ford - There may be three wires on the O2 sensor; two gray wires and one black. The black should read ground. One gray wire should read 12V with the ignition on, and the other gray wire is the one we are after. Probe this wire with the engine warm, and running with a voltmeter’s (+) probe, and ground the negative probe. While the vehicle is running, the reading should be approximately 0.5V. A reading below this indicates a lean air fuel mixture; a reading above this indicates a rich mixture. If no reading is present, and all connections are good, the sensor is probably in need of replacement
Source: by broncoii.org

[bergs]

miesk5, on Jul 25 2008, 11:41 AM, said:

bergs, take a look @ one of replies aboce on teesting the O2 sensors; see if thay have the 3 wire leads.

Testing, Bronco & Ford - There may be three wires on the O2 sensor; two gray wires and one black. The black should read ground. One gray wire should read 12V with the ignition on, and the other gray wire is the one we are after. Probe this wire with the engine warm, and running with a voltmeter’s (+) probe, and ground the negative probe. While the vehicle is running, the reading should be approximately 0.5V. A reading below this indicates a lean air fuel mixture; a reading above this indicates a rich mixture. If no reading is present, and all connections are good, the sensor is probably in need of replacement
Source: by broncoii.org

ok, i'll try this when i get home. I also noticed that in the wire loom that goes to the ignition coil there is a black wire that is sticking out and not connected to anything. could that be part of the problem?

[miesk5]

bergs, on Jul 25 2008, 10:38 AM, said:

ok, i'll try this when i get home. I also noticed that in the wire loom that goes to the ignition coil there is a black wire that is sticking out and not connected to anything. could that be part of the problem?

I think that vacuum leak needs to be addressed 1st
then we can look at that wire; take a pic of it and post it here if you can berg

next;
btw, we have 3 O2 Sensors in our 96 5.0/5.8; One in each exh manifold and one before cat
Locations, 96 Bronco, F Series, Explorer, Expedition, etc. Source: by Ford it shows the 4th for CALIF SMOG

(Calif Emission freaked-out Broncos have 4 O2 sensors)


O2 Sensor Cleaning by oxygensensor4less.com

[HardMaple]

miesk5, on Jul 25 2008, 02:14 PM, said:

I think that vacuum leak needs to be addressed 1st

Miesk is right, fix the vacuum leak first. This probably isn't the problem, but how stupid will you feel 6 hours from now when you find out it is the cause. Then reset your codes. If they come back, move on in an efficient manner.

Is the Yellow wire just Yellow or Yellow/Lt Blue? Plain yellow wire is unrelated to O2 sensor circuits. Yellow/Lt Blue is the ground wire for sensor #21 (do not try to convince yourself a plain yellow was supposed to actually be yellow/lt blue). If it is the y/lb, check for connectivity to Pin #94 and then to sensor harness. Repair if required.

135, 141, and 155 follow a very similar diagnostic routine. When together, the problem is:

Blown Fuse
Short to VPWR in Harness or HO2S
Water in harness connector
Open VPWR or GRD circuit
Low Battery Voltage
Poor Electrical Connection
Sensor
PCM

Tripping all 3 means it is likely a common wire, there are 2 and both are shared by other components. The first common wire is Grey/red that serves as a signal return wire for nearly every other sensor. This is supposed to located somewhere near Injector #4. This connects to Pin 91 at the PCM.
The second common wire is the VPWR. This is a Red wire (surprise!). It is fed by Pin 71 and 97 simultaneously. It also feeds the injectors, MAF, Evap Canister Purge Valve, and the Transmission Controls.

So my suggestion is this:
1) Find the easiest O2 sensor to access (probably #11);
2) using an Ohm meter, check for continuity between red wire at sensor connector and pins 71 and 97 and between Grey/red wire and Pink 91;
3) If an interruption is found, trace and repair any broken connections;
4) If no open circuit is found, disconnect negative battery cable and then disconnect wiring harness from PCM. Using Ohm meter, check for continuity between red wire at sensor connector and ground (but not the - battery post since you just disconnected the battery). Also check between grey/red wire at the sensor and ground. If either of these show continuity, repair short to ground.
5) Reconnect all connections.

If no open or short to ground circuit is discovered, let me know and we will enter a more detailed diagnostic.