94 STS IO 34 error and no PCM Data

94 STS IO 34 error and no PCM Data

Posted in the Cadillac STS Forum

John Buckley

Columbia, SC

#1 Jun 25, 2010
Hi all, hope someone can help with my saga.

94 STS 134K miles was running great except for bad heater blower motor.

Went off for long weekend, came back and started the STS to go to store, car ran horrible, a bad stumble/hesitation on acceration and rough idle. No codes set.

Came home and decided to pull battery cables and clean and check for proper grounds.
Started car got error codes and in the DIC it said "traction disabled" Stop engine, low oil pressure. Checked codes and got IO34 loss of PCm data, IO52 keep alive memory, TO72. went in to OBD to clear codes and of course I have a "No PCM data" all paramaters are there, ABS, SIR, ACP, TCS, RSS, went in to each one to the clear codes and did that now I just have the IO 34 code and dashes in the MPG and Range Displays. No info in the DIC from any PCM parameter ie: Temp, MPg...

The car will start and run, but only in the default mode of 2nd gear only, bangs very hard when you put it in gear.

I checked the main grounds on each side of the radiator, replaced the battery cables still have the problem.

I checked the voltage at pin M of the ALDA connector to ground, got 3.79v to 4.29v it varies constantly. I did this to see if the data line was locking up.

Decided to swap out PCU with a friends, his STS was rear ended but the front end is ok, still have the same problems, but I got a ACP code and dashes in the Temp display with his PCU, car would start but still has the problems, swapped back to my PCU.

I then swapped the IPC out still have the same problems, I put mine back in.

I am at a stand still I do not know where to go next, any ideas would be great.

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