98 12 valve cummins no bus, need help please

[KyleM94]

As title states im in serious need of help. Was driving along in my 98 12 valve when i lost all input from the cluster. I have done self check and the cluster passed and gives codes 920-921-999. I have cleaned grounds in engine bay, have a brand new vin coded pcm swapped in a different engine harness that i went through and cleaned every connection and re wrapped. I have swapped in a cluster from another 98 as well as a 99 24 valve. I have un plugged modules without any change checked relays swapped them around as well as checked fuses. One thing that is odd is usually everything i read with regards to no bus is the lack of a WTS light. On my truck KOEO the WTS and OD off are lit up immediately and dont go out then after a bit i get ABS/Brake, Low Fuel, and the seatbelt warning light. I really need help figuring this out to get my cluster back, this happened maybe 15 mins after i was messing with my pillar pod guages and one of then shorted out and popped the fuse tap that it was in, fuse 14 in the junction block but everything else worked fine and I’ve replaced that fuse and my glow shift guages function properly as well as all other electronics on the truck. Any help is greatly appreciated 

[Mopar1973Man]

Double check all your fuses with a ohm meter make sure you getting your power up again. There are a fuse under the hood in the PDC and then the fuse in the end of the dash. You can look at the CCD Bus article in the 24V section it will help you to understand bus voltage and understand how it works. As far as I know the cluster sets the bus voltage so you might have to send the cluster in for repairs. There is Module Masters right here in Moscow ID which can repair your cluster if it's found damaged. 

[KyleM94]

I will do that in the morning, if i take the 12v cluster out and put my 24v one in i get the same codes and issues minus OD off light but that might be just cause its a cluster from a manual truck. If i unplug every module leaving just PCM and cluster that would rule out one of the modules causing the ccd network to throw a fit correct?

[JAG1]

I once shorted out my ECM on crazy moment I had and my instrument cluster was running crazy. Everything on the gauges was off normal readings. So this may not help But, I disconnected my batteries for a lengthy time and drained all the capacitors by turning everything on with both batteries disconnected. I was happy to find this corrected everything and solved what I thought was a major problem, i.e. a shorted out ECM

 

I think you have a fried fuse somewhere hopefully

Edited February 19 by JAG1

[Mopar1973Man]

Just keep in mind the most this does is a fresh reset. Disconnecting the batteries will not clear error codes. Do make sure you have done your repairs first. I know both ECM and PCM will reboot fully if the ignition is off more than 10 seconds. I also know even the ECM, PCM and cluster are hooked to battery power so it might have some merit but again make sure you get the bus working again.

[KyleM94]

8 hours ago, JAG1 said:

I once shorted out my ECM on crazy moment I had and my instrument cluster was running crazy. Everything on the gauges was off normal readings. So this may not help But, I disconnected my batteries for a lengthy time and drained all the capacitors by turning everything on with both batteries disconnected. I was happy to find this corrected everything and solved what I thought was a major problem, i.e. a shorted out ECM

 

I think you have a fried fuse somewhere hopefully

Im hoping its a fuse i missed i had batteries out completely for 24 hrs while i waited to get my pcm. It is frustrating i hate diagnosing electrical issues, give me mechanical and im happy all day. I have the full FSM and skimming the wiring diagrams is a adventure all in it self.

[Mopar1973Man]

If you hung up give me a call. My number is in the contact us link at the bottom of any page.

[JAG1]

11 hours ago, KyleM94 said:

Im hoping its a fuse i missed i had batteries out completely for 24 hrs while i waited to get my pcm. It is frustrating i hate diagnosing electrical issues, give me mechanical and im happy all day. I have the full FSM and skimming the wiring diagrams is a adventure all in it self.

That's why even if had a Trillion bucks I wouldn't be buying any new rigs with all the electronics on them. I would luv a fully restored 55 chevy Nomad and I wish my wife could look that good too

Edited February 20 by JAG1

[Mopar1973Man]

Everyone runs from electronics. That is why I can reach 30 MPG. Which is better than any 12V mechanical can do. Even 24V p-pump conversion I can beat that too.

 

Electronics it what makes it possibly for some of the abilities of these engines. There is a reason carburetor vehicles have disappeared being they could keep up with efficiency. Then just understand even today most all gasoline engines are only 20% to 25% efficiency then look all have catalytic converter because there is that much sunburnt fuel in the exhaust.

 

Diesels without smoke can do well in the 30% to 40% efficiency. The fuel has more BTUs per gallon. No air/fuel ratio. Direct injected and compression ignition.

Edited February 20 by Mopar1973Man

[Great work!]

CCD shows up at OBDII port and on some early quad cabs a seat belt module under the middle seat. Don't forget to unplug them.

 

Sometime before a fuse blows small wires will get hot and burn through other wires in the harness creating a short. Particularly where the harness is wrapped  tight. Check the voltages on the CCD wires with all the modules unplugged except the cluster. Should be approximately 2.5volts

(With key on engine off) refer to detailed troubleshooting guide in manual and on this site. If the voltages are near 0 or 12 volts you probably have a short so start unwrapping wiring.

 

If your truck has the overhead temp/mileage display that is CCD too so disconnect that. In fact the wiring for that runs up the A Pilar where your guages are. Investigate that wiring since that's where it all started.

[KyleM94]

3 hours ago, Mopar1973Man said:

Everyone runs from electronics. That is why I can reach 30 MPG. Which is better than any 12V mechanical can do. Even 24V p-pump conversion I can beat that too.

 

Electronics it what makes it possibly for some of the abilities of these engines. There is a reason carburetor vehicles have disappeared being they could keep up with efficiency. Then just understand even today most all gasoline engines are only 20% to 25% efficiency then look all have catalytic converter because there is that much sunburnt fuel in the exhaust.

 

Diesels without smoke can do well in the 30% to 40% efficiency. The fuel has more BTUs per gallon. No air/fuel ratio. Direct injected and compression ignition.

I actually plan on converting to a 24v once i figure this issue out, i mostly hate the needle in hay stack chasing electrical issues. Im going to go out today and check fuses been little under the weather 

2 hours ago, Great work! said:

CCD shows up at OBDII port and on some early quad cabs a seat belt module under the middle seat. Don't forget to unplug them.

 

Sometime before a fuse blows small wires will get hot and burn through other wires in the harness creating a short. Particularly where the harness is wrapped  tight. Check the voltages on the CCD wires with all the modules unplugged except the cluster. Should be approximately 2.5volts

(With key on engine off) refer to detailed troubleshooting guide in manual and on this site. If the voltages are near 0 or 12 volts you probably have a short so start unwrapping wiring.

 

If your truck has the overhead temp/mileage display that is CCD too so disconnect that. In fact the wiring for that runs up the A Pilar where your guages are. Investigate that wiring since that's where it all started.

I will check for seatbelt module ive tried ABS and CTM i pulled the fuses for Airbag and the light came on but with them in the Airbag light is off and it doesn’t change anything i dont have the overhead console but im definitely going to look at the A pillar 

[Mopar1973Man]

here is my CCD network article to read over...

 

[KyleM94]

50 minutes ago, Mopar1973Man said:

here is my CCD network article to read over...

 

I have used that a little bit to try and troubleshoot ignoring the ECM section obviously. I know everything under the hood going to the PDC is good. Just out of curiosity there is no way to bypss any of the CCD is there to get speedometer/tach working again is there

[Mopar1973Man]

Speed signal comes from the ABS computer then sent typically to the cluster on the CCD bus.

[Mopar1973Man]

Biggest thing is to see if you got the bias voltage of 2.49 and 2.51 on the bus. Then hunt down why the bus might have a voltage offset be it 0V, 5V or 12V either a short to power or short to ground. Could be a open circuit. I'd suggest getting in contact with our Vendor @Auto Computer Specialist and ask some question to give more clues.

[KyleM94]

23 hours ago, Mopar1973Man said:

Biggest thing is to see if you got the bias voltage of 2.49 and 2.51 on the bus. Then hunt down why the bus might have a voltage offset be it 0V, 5V or 12V either a short to power or short to ground. Could be a open circuit. I'd suggest getting in contact with our Vendor @Auto Computer Specialist and ask some question to give more clues.

Fuses came out good, i will probe the CCD bus and post the readings i get 

[KyleM94]

On 2/21/2024 at 11:42 AM, Mopar1973Man said:

Biggest thing is to see if you got the bias voltage of 2.49 and 2.51 on the bus. Then hunt down why the bus might have a voltage offset be it 0V, 5V or 12V either a short to power or short to ground. Could be a open circuit. I'd suggest getting in contact with our Vendor @Auto Computer Specialist and ask some question to give more clues.

So just to verify i should unhook all modules except cluster. KOEO plugs at PcM should be 2.5v +/- .01 V then i check the individual module plugs to see that they are all seeing correct voltage?

[Great work!]

Yes, if the voltages are correct then notice which module kills it when plugged in. If the voltage is wrong to start with or is wrong when plunging in a known good module then open up the harness. 

[Mopar1973Man]

2.49 and 2.51 respectively after all communication is done.

[Great work!]

I re- read your first post and saw you had a tap on a fuse. Double check that fuse position sometimes those taps spread out the prongs or melt back into the plastic. Use a small pick and make sure the prongs have a good grip on the fuse.