P0401 code - Told to replace PCM

[Hefy302]

Hello,

After replacing a failed (plugged) catalytic converter, cleaning plugged egr ports and replacing a egr vacuum solenoid I am being told PCM has to be replaced for it is "not completly grounding the erg soleniod" and thus egr code still present during self test.

So can someone replace the PCM soleniod easily enough without paying a shop $876 to do so?

If so what part should I get and where?

My stang is 2000 Convertable, v6 3.8l automatic transmission. I am a Washington state resident.

Kind regards,
Hefy302

 

[wmburns]

Trouble shooting P0401 EGR

Working on the EGR system can be difficult. The tests are somewhat involved and may be lengthly. Do you have a Volt-Ohm meter and are you willing to use it? All of the tests will need to be done and the results posted.

I am assuming that you want to replace only the parts that are bad. Therefore, the tests will help rule out or confirm that the PCM is indeed bad.

We are going to assume that all EGR passage ways are clear. Remember, if there aren't, this could cause the problem.

Start first by cleaning the electrical connectors to the EGR vacuum regulator and the DPFE sensor. Use electrical contact cleaner. Regrease with a small amount of silcone di-electric grease (the same kind used on spark plugs). Do not cut corners on this step. The odds favor this as the root of the problem.

Next, it is vital that all vacuum hoses be in good condition. The exhaust gas is hard on rubber/metal parts. Ensure there are no leaks in the hoses to/from the DPFE sensor. Check all other vacuum lines and ensure they are leak free.

Reset the codes. Drive. Pull the next DTC to come up. If it is still P0401, go onto the next steps.

Rent a hand operated vaccum pump. Pull the vacuum line to the EGR valve. Apply a vacuum to the EGR valve. A change in engine running should immediatly be apparent. This is to confirm the EGR value is responding to vacuum.

Install a "T" fitting in the EGR vacuum line and attach the hand vaccum pump. Start the motor and record the vacuum. Rev the motor an observe the amount of vacuum. Looking to see if it changes. It should go up when the motor is reved and then slowed.

Next test, remove and plug the UPSTREAM DPFE vacuum hose. Reset DTC codes. Post the next code to appear. This code will give clues where the problem is.

>>>From Ford service CD
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 solenoid
Damaged PCM

Perform KOER self-test and look for DTC P1408 as an indication of a hard fault. If P1408 is not present, look for contamination, restrictions, leaks, and intermittents.

 

[Hefy302]

WM,
Thank you for the detailed information much obliged. Understanding that the gentlemen at the shop have pretty much went through the ERG system and ruled out every possibility but a damaged PCM, should I rely on their troubleshooting and decide to replace the damaged PCM where does one begin? Do I get an aftermarket PCM or a genuine ford motor craft replacement? If aftermarket whom do you suggest and what part #? Are they easy to replace and how does a novice mechanic go about replacing it.
I am definitely going to clean the electrical connectors, in doing so should my check service light go away, I don’t have any tools to check the code and I do also want to double check work done to ensure no vacuum leaks before ponying up (pardon the pun) to procure a new PCM. I read somewhere about using the battery cables in a particular configuration to reset the PCM in doing so the check engine light goes away until it is trigger again by whatever if failing, is this correct?

Thanks again for you assistance.
Hefy302

 

[wmburns]

A couple of things. There isn't such a thing as an aftermarket PCM. Name brand Ford or nothing. The only question is new, re-man, or salvage.

If you trust the mechanic, then replace it.

If you doubt the mechanic's diagnosis, then you are going to have to do the steps.

The PCM itself is actually easy to change. It's the re-programming that's a PIA. Remember that the cluster, GEM, and PCM have to be programmed for each other.

If not re-programmed, the car will not start because of the anti-theft system (PATS).

FWIIW, the explaination of not enough grounding from the EGR regulator sounds fishy to me. In fact, it sounds like a bad/weak electrical connection. But this is your project.

Should you replace and go the new route, the dealer will handle the re-programming.

If you go the re-man route, confirm the replacement PCM will arrive with PATS disabled. This will allow you to swap the PCM and drive to the dealer to complete the programming.

If you go the salvage yard route, try car-part.com to compare prices. With regards to PATS, two choices. Tow the car to the dealer or buy a hand held tuner and disable PATS yourself.

Yet another option is to get a salvage yard PCM (with the matching calibration) and the cluster. Swap the PATS module from the salvage to your cluster. Then the PCM and PATS receiver will already "know" each other.

As a reminder, the PCM has to match with details such as Model Year, calibration, and transmission. Sometimes features such as ABS brakes matter.

With regards to resetting of the DTC codes. This is done with a ODB2 scanner or tuner. Most autoparts will read/reset codes for free. Or check into getting your own ODB2 reader. They are not really that $$. Lastly, disconnect the battery negative. Remember the PCM will have to re-learn idle trim values so expect it to run rough for a little while.

Don't buy a cheap ODB2 reader if you are seriously thinking of buying a tuner. The tuner will do everything and more than the reader.