I can not find g108 spent 20mins looking. Tonight I tested bus wires to tcm and the are fine. Tomorrow is grounds.

 

Well I checked this grounds and cleaned them all. I found my coil is not bolted to the bracket. But I don't see how to get a buy behind it. Any one have a pic or can tell me how it should be secured. Also I got my hands ob a cluster I know is fine did the relearn and only the dummy lights are working still. Still have code for pcm to tcm issues. When I drove it last week it shifted fine. Could the tcm be the issue. Also I am starting to run out of ideas. However it has been welded on so maybe pcm issues? Heck guys I'm lost what's next boys?

 

The coil mounted to the coil mount bracket which is secured to the engine block by the two ground studs (G101) and the coil is secured to the coil mounting bracket with two bolts.

Make sure the coil mounting bracket isn't corroded on both sides of the bracket where it is fastened to the engine block ground studs (G101).

When you drove it last week was it still it run rough, spark knock, and back fires?

 

Yes it was the only time I have drove it or ran it really. It was to the end of my private drive and back after letting it warm up. The two ground studs below the coil have been cleaned. Are yo saying the the coil grounds to the mounting bracket? If so this is a major issue as it is not bolted in. The people who owned it last were clearly hill jacks. I still have the issue of no pcm to tcm communication. Still no gauges. And I'm out of ideas. I will bolt the coil it the bracket tonight after cleaning it. It looks almost impossible to get nuts behind it so I'm sure that will be fun.

 

You remove the coil bracket from the engine, mount the coil to the bracket, then reinstall the bracket to the engine (ground studs).

When I changed my coil I made sure the mating surface between the coil and the bracket were free from corrosion, paint, etc., and the same between the bracket and engine & ground studs. I wasn't sure if the coil needed to be grounded but when I removed the old coil these surfaces were bare metal and rusty so I cleaned them up before reassembly.

Did you say you disconnected the CPS to see if the instrument cluster came back alive? I guess the CPS can cause problems like this ut I don't know how. Might be worth a try if you haven't done this.

Looks like the hill jacks (Bubba) made a mess of things.

 

I have a new CPS on it and I also unplugged it nothing changes. I also tested both the old and new CPS with a meter and they test good. Other than the coil what should I do next? I am lost at what to do next. Btw still can't find the ground by the light switch.

 

You should make a numbered-itemized list of all the things you've done so far, including what components you've changed, and the pins of what module connectors you have checked and what voltage/resistance readings you saw.

To access G108 you may want to remove the Steering Column Opening Cover (just below the steering column), held on with scews and snap clips, and the Knee Blocker behind it, held on with scews. Using a mirror and flash light look up under the dash and to your left of the headlamp switch. There should be two ground studs on the dash frame.

 

1. I checked and tested every fuse. Both with a test light and meter.
2. I checked and cleaned the harness that plugs into the cluster.
3. I tryed the cluster test which will turn the dummy lights on but no gauges move or read.
4. Checked for bus voltage at the dlc. It's 2.4 at both (+) and (-) pins.
5. Back probed my air bag mod and found good voltage in the bus there. (Can't remember the exact voltage )
6. Pulled codes and found p1694 p1492 p0138 p0113 p0443
7. Cleared all codes
8. Idled untill running problem surfaced again.
9. Pulled codes and found p1694.
10. Replaced and checked cps with new cps
11. Pulled tcm harness out of fire wall removed all tape and plastic. Looked all wires over. Ohmed wire from pcm to tcm and found .12 ohms in both wires. Retaped and covered wires ran harness back to tcm.
12. Cleaned tcm plug and pcm plugs.
13. Replaced cluster with a known good cluster from same year Cherokee and did relearn.
14. Drank a beer and cried myself to sleep.

I may be forgetting a step or two in there. Do any of those other codes alarm you? They didn't come back but may relate? I am going to go check under the dash for the ground now. After that I am out of ideas. I have never had something beat me this bad and have tackled some serious issues on multiple diesel trucks. I am totally lost here Ken. BTW when this is all done I will have to buy you a beer I'm near Hillsdale mi. Not to far really.

 

Alrighty I am back. I found that my fuse block inside was bad. I replaced that and put a down stream o2 sensor in. Running problem solved. I now have power to my cluster but it says no bus. I have a few questions. Before performing the tab for this issue I had the dealer check it out. They say I have the wrong pcm. How can I myself verify the part number for my pcm as I think they are wrong. Also would this cause a no bus issue? Next will a 2001 cluster cause any issues?

 

There should be a sticker on your PCM that has its part number. Should be like 56041534AB. If you get a replacement PCM, you may want the dealer to Flash the PCM for you...around $100....if systems don't work properly.

The 2001 instrument cluster is a different part number than the 1998 instrument cluster so the 2001 may not be compatible. There may be internal wiring differences between the two (CCD Bus wiring)

1998 Highline W/Tach P/N 56009727AC
2001 Highline W/Tach P/N 56010192AC

 

The dealer says my PCM doesn't match my vin part number wise. I have reason to doubt them. I would like to run my vin and get the correct part number myself. Any ideas on how to do this. Also both clusters (98 and 01) preform the relearn fine 01 says no bus 98 does not. I can't get them to work other than the relearn.

 

For others reading this great thread, can I ask what you did to confirm your fuse block was bad. It will surely help others going down your path.
Thanks,
Dylan

 

I unhooked the battery and used a power probe to but 12v through the block. I used a multi-meter which showed me crazy reading. I pulled the block out to find it had TONS of corrasion. I am sure this is due to the fact it was smacked on that side and the PO was a hilljack.

 

What block? The Junction Block?

 

No the one in the kick panel. After I replaced it I had power to the cluster.