Trouble Codes: P0401 and P0411

FSB_Rookie · May 21, 2011

I acquired a 1996 full size bronco 2 years ago with 136k miles. It was in very good condition considering we are in the northeast. Within 3 weeks after I got it I had to replace the EGR valve. Now with 163k miles I have trouble codes P0401 and P0411. I have been driving and resetting, driving and resetting, driving and resetting waiting for the snow to finally melt to tackle this problem. Well today is the day. I read all the available postings I could find on these two trouble codes.

I check all the vacuum lines I could reach. Aside from one that is questionable, but tested as intact, I can't find any vacuum leaks. I tested the EGR valve with vacuum pump and it does not move at any level of vacuum pulled. I have a new one ordered and I will hopefully replace that tomorrow.

My question is: Can the malfunctioning EGR cause or create any conditions that would trigger the P0411 Secondary Air injection incorrect? Do I have two separate problems?

I need to get this fixed soon as my inspection has expired and it will not pass the emissions inspection. The Highway Patrol does not have the same libertarian view of emissions inspections that I do and I can only drive the back roads for so long!

Thanks for your assistance.

miesk5 · May 22, 2011

yo,

Welcome to the Zone!

P0401 EGR Flow Insufficient Detected Possible Causes; "...DTC P0401 is for exhaust gas recirculation (EGR) insufficient flow detected. This most likely means one or more of the following has happened: The EGR valve may not be opening due to a lack of vacuum; There is a blockage in the EGR (most likely carbon buildup); The DPFE sensor is faulty and needs to be replaced; The EGR valve is faulty. In fixing this code, it is quite common for people to just replace the EGR valve only to have the OBD code return. However, just like many other DTCs, the problem is not always obvious and the EGR valve is not always the culprit..." READ MUCH MORE Source: by Gateway Clean Air Program dnr.mo.gov

DPFE Sensor Overview, Construction, Testing & Depiction, Older Aluminum Version; "...DPFE SIG is This voltage at idle is approximately 0.45 volts; SIG RET is GROUND; V REF is 5 volt reference. DTC PO1400, P1401, PO402, P1403, P1408; "There are a number of tests that the EGR system is put through. First the DPFE is checked. It is continuously monitored for opens or shorts. The OBD II system looks for the DPFE signal to exceed the minimum or maximum values. If it finds these values out of specs a DTC P01400 or 1401 will be set The OBD II system also monitors the EGR flow rate. At a steady state condition when the engine load and speed are moderate and the EVR duty cycle is high the DPFE voltage is checked. It then compares this DPFE value to a stored desired DPFE value for those conditions. If the two values are inconsistent, the EGR flow is insufficient (Fig. 11). A DTC P0401 will be set for this condition. This test is also performed during a Key On Engine Running (KOER) test. If it fails during this test a DTC 1408 will be set; The OBDII system monitors continuosuly the DPFE signal at idle. Since there should be no EGR flow at idle, the DPFE signal should show a no flow voltage signal. The system compares the Key On Engine Off (KOEO) stored voltage to the DPFE signal at idle. If the signal is not consistent with this value, it may indicate a stuck open EGR valve. The DTC for this condition is a P0402. The EVR is continuously tested for opens or shorts. The OBDII system looks for a circuit voltage that is out of range or inconsistent with the EVR commanded output state. If it finds a fault in the EVR circuit voltage a DTC P1409 will be set. There are a number of tests that the EGR system is put through. First the DPFE is checked. It is continuously monitored for opens or shorts. The OBD II system looks for the DPFE signal to exceed the minimum or maximum values. If it finds these values out of specs a DTC P01400 or 1401 will be set. The system then looks for a DPFE voltage value that is inconsistent with a no flow situation. If the DPFE voltage increases or decreases this may indicate a fault with the upstream hose. A DTC P1405 will be set for this condition. A DTC P1406 will be set if there is a problem with the downstream hose. The OBD II system also monitors the EGR flow rate. At a steady state condition when the engine load and speed are moderate and the EVR duty cycle is high the DPFE voltage is checked. It then compares this DPFE value to a stored desired DPFE value for those conditions. If the two values are inconsistent, the EGR flow is insufficient (Fig. 11). A DTC P0401 will be set for this condition. This test is also performed during a Key On Engine Running (KOER) test. If it fails during this test a DTC 1408 will be set. The OBD II system also checks the DPFE signal when the EGR valve is open for a negative voltage. If a negative voltage is detected the hoses may be reversed. If it fails this test a DTC 1403 will be set. The EVR is continuously tested for opens or shorts. The OBDII system looks for a circuit voltage that is out of range or inconsistent with the EVR commanded output state. If it finds a fault in the EVR circuit voltage a DTC P1409 will be set..." READ MORE Source: by tomco-inc.com

P0401 - EGR Flow Insufficient Detected The EGR system is monitored during steady state driving conditions while the EGR is commanded on. The test fails when the signal from the DPF EGR sensor indicates that EGR flow is less than the desired minimum. Vacuum supply

EGR valve stuck closed

EGR valve leaks vacuum

EGR flow path restricted

EGRVR circuit shorted to PWR

VREF open to D.P.F. EGR sensor

D.P.F. EGR sensor downstream hose off or plugged

EGRVR circuit open to PCM

VPWR open to EGRVR solenoid

D.P.F. EGR sensor hoses both off

D.P.F. EGR sensor hoses reversed

Damaged EGR orifice tube

Damaged EGRVR

===============

P0411 - Secondary Air Injection (AIR) system upstream flow See DTC P1411 P0412 - Secondary Air Injection System (AIR) circuit malfunction The PCM attempts to control when air is injected in the exhaust. The DTC indicates a Secondary Air injection system AIR circuit fault. AIR circuit open

AIR bypass solenoid fault

Damaged PCM

AIR circuit short to power

Solid state relay fault

Damaged AIR pump

DTC P0411 & P1411; "... indicates Secondary Air not detected. In order to test the pump, it must be capable of driving the HO2S lean; NOTE: Some applications have one or two Air Diverter (AIRD) valves. Key off. l Visually inspect EAP hoses from the EAP to the AIRD valves. l Inspect air hose for cracks, binding and obstructions. l Are EAP hoses OK? Yes GO to «HM8». No SERVICE or REPLACE damaged parts. COMPLETE PCM Reset to clear DTCs (REFER to Section 2A, «Powertrain Control Module (PCM) Reset»). RERUN «Quick Test; HM9 CHECK FOR VACUUM AT AIRD VALVES l Key off. l Reconnect PCM. l Disconnect vacuum control line from the AIRD valve(s). l Key on, engine running. l After a 5 second delay, vacuum will be present between 30-90 seconds. l Is vacuum present at the AIRD valve(s)? Yes GO to «HM10». No GO to «HM30 Source: by Fishallot

Following from 96 Bronco Powertrain Control/Emissions Diagnosis (PCED) Manual; most repair shops will not perform these pin-point tests. An Automotive Electric shop may do this, but local shop have decided to get out of diagnostic business and just dwell on electical repairs and installation.
Where breakout box is cited, go to the PCM CONNECTOR pin instead; for instance - Measure resistance between the SIG RTN circuit & Pin 91 359 (GY/R) Sensor Signal Return at the breakout box
Have shop use the PCM (EEC V) Connector Pin Depiction with Pin Numbers

DPFE SENSOR w/terminal ID Testing & Vacuum/Voltage Parameters & pics on both older Aluminum & Newer Plastic Version; miesk5 Note, Tomco Figure 4 for Plastic Housing version, it shows +/- 0.25 volts; It should be 1.0 +/- .025 volts as desribed in the narrative and in Ford EVTM; "...Access DPFEGR PID (formerly DPFE) with a Scan Tool. PID voltage should be 0.2-1.3 volts..."
Source: by tomco http://www.tomco-inc.com/Tech_Tips/ttt36.pdf
I used this to test my DPFE; same as Ford EVTM

FSB_Rookie · May 22, 2011

Thanks for the information. That is a lot to digest. The pictures are especially helpful in identifying these parts. By any chance do you have the name and address of the engineer that suggested putting the diverter valve between the engine and the firewall? I would really like to send him a fruit basket or other token of my appreciation.

I am going to be tackling the EGR problem first.

Thanks again.

Rons beast · May 22, 2011

I had these codes on my 96 as well. Fought them like you did. Replaced the EGR sensor....twice...(they were under warrenty from the manuracturer)

My egr worked fine but still would set the codes after about 50 miles of running or so.

Then I read about heavy carbon build up on the throtle body and in the passages. I removed the throtle body, cleaned it and the passages, and reset....problem solved. It has been about a year now, and no codes.

Good Luck

miesk5 · May 23, 2011

FSB_Rookie said:
By any chance do you have the name and address of the engineer that suggested putting the diverter valve between the engine and the firewall? I would really like to send him a fruit basket or other token of my appreciation.

Thanks again.

yo,

That valve & ck valves are in a great back-straining area...lol.. hey! Where is my pal BroncoJoe when I need him for an L2 issue?

I removed my hood and used two small kitchen type ladders with a plank across to work on all that Secondary Air Injection stuff.

Parts Break-Out Diagram in a 96 w/Ford part numbers

Source: by Ford via miesk5 at broncolinks.com

Follow those Ford Bronco 1996 Service Manual/ EVTM pin-oint tests for both codes to get to the problem w/out buying $$ parts or doing extra work.

Here it is, but with the electric air pump info removed;

DTC P0411 indicates that Secondary Air is not being diverted when requested.

Possible causes:

--Vacuum hoses damaged.

--AIRB/AIRD valve inoperative.

--Air Pump inoperative.

--AIRB/AIRD solenoids damaged. (Location pic in a 5.8; miesk5 Note; same location as in my 96 5.0

Source: by Steve83 (Steve, That dirty old truck) at SuperMotors.net

Thermactor Air Diverter Solenoid (TAD, AIRD, AM2)w/Yellow vacuum line &

Thermactor Air Bypass Solenoid (TAB, AIRB, AM1) w/Pink vacuum line

Test; Key off. Disconnect both AIRB/AIRD solenoid connectors and measure both solenoid resistances. each resistance should be between 50 and 100 ohms.

Visually inspect vacuum lines for disconnects in the AIR system.

Visually inspect for proper vacuum line routing. Refer to VECI decal.

Visually inspect Air Pump for broken or loose Air Pump Belt.

-----

The up-stream and downstream functional air flow test is performed during idle, once per engine start-up &only after all HO2S Monitor tests have been successfully performed. The flow test relies upon the up-stream & down-stream HO2S to detect the presence of additional air in the exhaust when introduced by the Secondary Air Injection system.

The DTCs associated with this test are DTCs P0411 and P1411

For parts number and Vac Diagram;

Vehicle Emission Control Information (VECI) Decal; Contains Vacuum Diagram & Calibration Parts List for 88 & UP.

On-Line for Free at Ford.

Click "Quick Guides" in left panel; Scroll to & CLICK VECI Labels "Provides Vehicle Emission Control Information (VECI) and a related calibration parts list." Enter applicable info (need to know your Calibration number from your B-pillar sticker).

Vacuum Diagram is the same as the one on the core support or hood or air filter cover. Suggest Right Clicking this Hot Link & Open in New Window

Source: by Ford at http://www.motorcraftservice.com

Trouble Codes: P0401 and P0411

FSB_Rookie

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miesk5

96 Bronco 5.0

FSB_Rookie

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Rons beast

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miesk5

96 Bronco 5.0

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