True code 12?

[WarWagon]

Computer will always flash and never store code 12. Well how do you know when you do have a real code 12?

That or my PCM is fried. I get a SES light that flashes and flickers from time to time. It does not stay on steady except when the engine is off and key on. Also get some erratic shifting from time to time. Weird shifting and the lights first appearance when hand in hand.

As all this PCM does is operate the 4L80e the weird shifting is a symptom.

The RPM sensor looks good - not cracked.

Rebuilt 4l80e. 140K on the clock. 1993 DB2 so the engine will run without a computer plugged in. Won't shift without it....

No codes are stored. The PCM did store trans slipping codes when the transmission ate OD.

So what do I check for a true code 12? RPM sensor/wiring and anything else?

 

[96 OILBURNER]

Code 12 is not a trouble code. It is a handshake code to let you know the PCM communicate as requested.

 

[bk95td]

Did you ever have a scan tool hooked up while the transmission was shifting weird? My 92 would loose the tps signal for some reason. Turn the engine off and restart and it would be fine again. When it lost the throttle signal it would shift very hard and not lock-up and no overdrive. After checking all connections and the tps it ended up being a faulty pcm. Obviously a bad connection inside the pcm that it would sometimes work perfectly,sometimes not. Remaned pcm from rockauto $150

 

[Jess_sr]

You have to read your PIDs with a scanner while you having the problem.

 

[buddy]

In my 94, the code 12 will only flash when there are no other codes

 

[bison]

I think you need a code scanner to read a pending code,only a steady SES light on sets a hard code
Code 12 is just an hi and goodby code