My ongoing saga with what I thought was a PCM problem continues. And now I'm not sure if the problem really is in the PCM.

Now with the refurbished PCM OUT OF THE TRUCK, I'm still getting an error and the mileage on the odometer. There's got to be a ROM chip or RAM or something that I can clear the odometer. I've pulled all the relays in the PDC and it still has the previous info.

I cannot clear the "no bus" error even with the PCM out.

Y'all have been good before - what about this one?

Thanks!!

 

well, if the pcm is not connected to the truck the odometer WILL display error, or no bus, indicating it cannot communicate w/t he PCM. did you try disconnecting the battery overnight to let the codes clear themselves??? that would be my first thing to try

 

I've had the negative disconnected when I'm plugging and unplugging sensors and relays but not completely disconnected. I'll try that tonight and see what happens.

And if the PCM is disconnected totally, what is generating the "no bus" error?

Thanks, shrpshtr325

 

the fact that there's no PCM.

 

But even when the PCM is online, I can't clear the error on the odometer - which probable brings me back to tracking down the wiring problem.

One thread mentioned disconnecting all the sensors and see if the error goes away. I must have only got 95% of them because I still had the error with sensors hanging all over the place! I'm leaning towards the Crankshaft Position Sensor - I don't think I was able to disconnect that one.. Anybody have any idea if there's a way to test the CKS?

 

not sure on how to test that one, but if you get the "no bus" error w/ the PCM hooked up then its most likely a wiring problem, and "no bus" is an error programed into the dashboard panel as the default display unless it gets another signal from the computer to override it(or at least i think thats how it works)

BTW: while you have the battery disconnected, hold the key to start for about 30 seconds, this will drain all the residual current out of the electrical system and reset everything

 

AHA - with BOTH battery cables disconnected.
I've done the negative cable off and hold the key for 60 seconds. Same thing?

 

should be the same,