TCM OR PCM?!?!?!?! I don't know what to DO!!!!

[VTEK1]

triyng to get up to see my girlfriend in Maine, i went to get outta Burger king to get some cash for tolls I hit the gas and the truck didn't move went to look to see if i slipped it into neutral by accident but no it was in drive. I hit the brakes shut the truck off and let it sit there for about 2 minutes started the truck went from park to drive and everything was okay. went to take a left into the ATM and it did the samething this time i noticed that the instrument cluster died. wasn't sure if it did it the first time. this the the odometer said "no bus". I drove it to autozone in first and got the diagnostic check done. P1698 was the error code. The definition was a open ccd bus line or failed TCM. buddy says he know where to get a TCM out of a parts 00' XJ for like 40 bucks. has anyone ever heard of this. if it's a bad ground or a short where do I start checking. I have no idea where to start looking and the dealer wants 400 for a brand new TCM plus the labor at $80/hour. HELP ANYONE!!!!! beer may be given as a reward if you live close. HELP!!!!!

 

[GrimmJeeper]

take your gauge cluster out and clean the contacts on the plug that goes into the back, and the socket on the cluster itself. its a pretty common problem with the 97+ models. the pcm does wacky things when it loses contact with the gauge cluster.

hope this helps.

 

[VTEK1]

I cleaned the contacts but they all look nice and shiny no corrosion of oxidation of any sort. where is the PCM located since I'm replacing the TCM tomorrow to make sure it isn't that. I figured since when I unplug the TCM the cluster works that is was needs to be replaced. But where is the PCM located and maybe I can test that and clean it or just replace that.

 

[lawsoncl]

I believe it's above the gas pedal on the drivers side on a 2000.

 

[VTEK1]

okay i thought that was the TCM so if the PCM is located above the gas pedal then thats what I'm replacing. so if that is the PCM above the gas pedal then where the hell is the TCM!!!!!!!!!

 

[lawsoncl]

Oh. I was talking about the TCM which is under the dash. Isn't the PCM under the hood on the drivers fender on the 2000?

The TCM controls the shift based on the TPS signal and speed sensors in the tranny. The PCM does not send it any info over the CCD bus. So bad shifting can't be caused the the PCM.

 

[88 Wagonman]

I thought the late model XJ's had a PCM (powertrain control module) and not a seperate ECM (engine control module) and TCM (transmission control module). Someone please correct me if I'm wrong.

 

[VTEK1]

as far as I know there is a PCM and a TCM in my 99 XJ. Like I said i don't know what I'll do if when I replace the TCM tomorrow and it doesn't work, I'll prolly start parting the thing out right there. I've fixed all the little things on the truck and really done a lot of preventive stuff but I don't know where to go from here if this doesn't work. It's gotta work since when I plug it the instrument cluster works and the tranny won't shift because it doesn't have the TCM, but the TCM isn't blocking the information to the cluster. So replacing it (correct if I'm wrong) should allow the information to the cluster and create shift schdueles and actually shift my XJ. Things would be so much easier if this thing was a manual. let you know what happens in the morning hopefully this will help someones else out instead of losing sleep like I am.

 

[VTEK1]

I don't know what I did but i cleaned the PCM terminals and sprayed with with compressed air from the can so it was dry air, and then put them back into the PCM, I also cleaned up the PCM and unscrewed it from inside the engine compartment. Put it all back together and everything runs great now. It's the weirdiest thing. If anyone know what might have caused this where the short might be coming from I really don't know what happened.

 

[RichP]

It did not have to be a short, it could have been an open that you fixed.

 

[lawsoncl]

I thought the late model XJ's had a PCM (powertrain control module) and not a seperate ECM (engine control module) and TCM (transmission control module). Someone please correct me if I'm wrong.

That's a common myth. The Cherokee always had a seperate TCU. Some folks mistakenly assumed it got integrated into the PCM when it disappeared from under the passenger side of the dash, but it really just got relocated to the drivers side.