1990 LeSabre CODE 65 EGR3 - Requesting a Resistance Check PLEASE!!!
 

The problem:

Intermittent Code 65 EGR3 error. I have also seen an intermittent Code 26 occur as well, but 65 and 26 never occur at the same time, and Code 26 gives no indication of which QDM sets the error...but I can guess.

Initial Diagnosis:

1. Removed, disassembled and cleaned EGR valve. Checked coil resistance. All check good (see pic below for readings). Tested each coil for solid pick / drop with 12V. All coils pick solidly with a snap and release immediately upon ground drop.

2. Ensured connector pins at valve and wire connectors were clean and tight.

3. Reinstalled valve, reset code, and drove for a couple of weeks before seeing another intermittent 65-3. Also saw a couple of 26's between the 65 setting the SES.

https://www.gmforum.com/attachment.p...ine=1467660465


Today's Diagnosis:

Determined to find the source, I once again removed and checked the valve. Resistance readings are indicated in the pic of the FSM page above. The valve looked clean as expected, and again, tested AOK with 12V applied. Deciding the issue is upstream from the EGR I got out the ESM and traced the wiring back to the ECM. Here are today's results:

1. With key on engine off I checked the resistance at each of the EGR valve pins through the ECM to ground. Pics of readings:

https://www.gmforum.com/attachment.p...ine=1467660465

https://www.gmforum.com/attachment.p...ine=1467660465

https://www.gmforum.com/attachment.p...ine=1467660465


As you can see, the line with the lowest value is EGR3, which is the one throwing the 65's. Coincidence? I think not...

I wanted to make sure I was not dealing with a wire issue, so I removed BATT (-), and unplugged the connector at the ECM and checked resistance at C1C2 which gave a reading of .2Ω, I checked EGR 2/3 and got similar readings, which tell me all of the wiring to the ECM is good.

At this point I am now convinced that the problem lies within the ECM.

So onto my request: Is there anyone here that can check the resistance values of the EGR lines at the EGR connector, between the connector and ground (as shown above), with the KOEO? I would expect to see all 3 values identical.

The EGR I have is this one:

https://www.gmforum.com/attachment.p...ine=1467660465

I would really appreciate if anyone would be willing to assist with getting those resistance readings for me...it's always helpful to have a non failing system to compare numbers with.

Thanks for taking the time to read! https://www.gmforum.com/attachment.p...ine=1467660465

Dave

To expand some on the Code 26's I mentioned above and how I believe it ties in to the Code 65--Code 26 is a QDM error. The FSM does ask in the flow chart if a Code 63, 64 or 65 are being set at the same time, and the answer is no. My intermittent 65's are always separate from the 26's set, and never together. The FSM does not reference any other codes other than those. Also, none of the systems run from QDM's 1, 2, or 3 are giving me any issues, just the EGR problem, which happens to be controlled by QDM 4...and hence the connection between the intermittent 26's and 65's.

My money is on the ECM....

Mine too. My replacement ECM will arrive Thursday.

Fixed. Replaced the ECM, all lines at EGR connector from QDM4 read identical now.

Life is good.

:thumbup2