Stumbling Idle ... need assistance

[dogfriend]

I would try removing the HO2S signal and signal return wires (both sides of the sensor) to make sure you are not getting a short on either side of the O2 sensor circuit.

If you still have Code 543 with the secondary fuel signal disconnected and the O2 sensor(s) disconnected, then by the earlier article that Mr. Shorty posted it appears that you have an internal fault in the PCM.

 

[Mic_]

I would try removing the HO2S signal and signal return wires (both sides of the sensor) to make sure you are not getting a short on either side of the O2 sensor circuit.

Thanks for the idea.

I just tried that, and found out that without the sensor return line pin #46 GY/R into the pcm, one can not run the self tests. That wire is the same one that goes to the VIP data link connector and is jumpered ( I believe to the STI trigger ) to initiate the self test code retrieval sequence.

For reference that GY/R line feeds the octane adjuste, ECT, IAT, TP, DPFE, NUETRAL SAFETY SWITCH, AS WELL AS A 'CLUTCH TRIPLE FUNCTION SWITCH JUMPER" .

I say jumper cause I have an a4ld, hence no clutch.

Any ideas what to check next?

I am still in denile that it's the pcm

 

[dogfriend]

Originally, I thought the problem was no signal from the fuel pump, but you have checked that and it doesn't matter if the wire is connected to the PCM or not, you still get the code. Mr Shorty posted the info from the Mitchell manual which says if the truck starts its either a shorted HO2S or the PCM.

I think you have ruled out the HO2S, but to be completely positive, you could test the sensor one more time. I would test resistance between the heater power wire and the other three wires on the HO2S. You should get a resistance between heater power and heater ground (cause you have a heater (resistor) in the circuit). My book says 2 to 5 ohms for the heater. You should get an open circuit (infinite resistance) between the heater power and the other two wires (sensor signal and signal return).

If the HO2S checks out, then the Mitchell manual says its the PCM.

BTW, my book says:

512 EEC(PCM) Processor Keep Alive Memory (KAM) test failure (CM)

Disconnecting the battery could set this code.

 

[Mic_]

I think you have ruled out the HO2S, but to be completely positive, you could test the sensor one more time. I would test resistance between the heater power wire and the other three wires on the HO2S. You should get a resistance between heater power and heater ground (cause you have a heater (resistor) in the circuit). My book says 2 to 5 ohms for the heater. You should get an open circuit (infinite resistance) between the heater power and the other two wires (sensor signal and signal return).

If the HO2S checks out, then the Mitchell manual says its the PCM.

Yea..I re-read those posts and picked that up.
Thing is that I disconnected both O2 from the pcm got the code.
Also disconnected both O2 from each of their harnesses and got the code.
( those are a pain to reach)

BTW, my book says:

512 EEC(PCM) Processor Keep Alive Memory (KAM) test failure (CM)

Disconnecting the battery could set this code.

Mine said corrupt KAM as well...figured it came from disconnecting the pcm so many times (as I was pulling these wires out of its harness)

I'm leaning alot more toward the pcm after all this.
Any one have and Idea on price $

Also can I trust one from a junk yard (or is that w/o warrenty)

 

[dogfriend]

fastpartsnetwork.com

 

[Mic_]

I am still in denile that it's the pcm

Well I bought one....

And now for the drum roll...

Replacing the PCM cured my 'permanant' fault code and my poor idle.

Money well spent and excellent advice for all of you folks!