Engine/Transmission (1998.5 - 2002) help - ugly check engine light came on

[dresslered]

Problem reoccured

After clearing the codes last weekend, I attributed the problem to a sticky relay. However, this morning on the way to work, I had the same Christmas light show--all indicators on the dash came on, the odometer read "no bus" and the overhead gauge read "CCD". This time I also noticed that ALL the instruments were dead. The truck appeared to continue driving just fine and after about a minute of driving, everything went back to normal other than it left me with a check engine light again. I think that I read that this could be a connector behind the instrument cluster? Any other ideas? Thanks,

David

 

[JLandry]

I think that I read that this could be a connector behind the instrument cluster?

David,



Now that you mention it, I remember reading about that same thing somewhere here on the TDR forum. Someone was getting a NO BUS message and all it took to fix was re-seating the instrument cluster in it's self-docking connector.



Try this next time the problem happens: Safely pull over to the side of the road and with the truck still running try pushing the instrument cluster firmly into the dash with both hands. If the problem immediately clears up (with the exception of the CEL of course), then it probably is just intermittent contact of the self-docking connector at the rear of the instrument cluster. If that's what it turns out to be, I'm not exactly sure how you'd solve it permanently... seems like it could work loose again. Hopefully just a healthy shove of the instrument cluster will solve it once and for all.



Alternatively, it could also be a loose connection somewhere on the instrument cluster itself.



Please keep us posted.



Good luck,



John L.

 

[SeanM]

I had something like this happen to me and I hope it isn't what is happening to you but I was driving down the road one day and my instrument panel went nuts my gauges went crazy and my dash light started blinking and then everything went back to normal and the truck ran perfectly fine. It happened again 2 days later and I got all sorts of codes and a no BUS signal on my odometer and my instruments went dead. Now some how some way (and yes everything on my truck is fused) my in dash wiring harness had a wire get hot and melted to a couple of other wires causing that stuff to go haywire If I would reach under the dash and shake the harness it would go back to normal. When I peeled the cover off the harness I could see the the melted wires. . I had to take it to the dodge dealership where they claimed it was because of my brake controller. and $3400 dollars later it was fixed the wiring harness alone was $2600.

 

[dresslered]

Thanks John, that seems to be the consensus that I have found doing a search on the problem. With mine, being an intermittant makes it harder to troubleshoot. I like your idea of just pressing on the instrument cluster to see if that resolves the issue.



Thanks to you as well Sean. A melted wiring harness would not be good, but I can't imagine how the brake controller might do this... mine uses the factory wiring?

 

[SeanM]

mine used factory wiring as well and I really don't know if the brake controller was the cause that just what they said. Good luck

 

[dresslered]

Good God, and now an update...



My intermittant had turned into a continuous problem:



1. All cluster gauges dead;

2. "no bus" displayed in odometer;

3. "CCd" displayed in overhead display;

4. "Check Engine" light on;

5. "ABS" light on;

6. "low fuel" light on;

7. "Air Bag" light on;

8. Furthermore, the heates seats will not switch on.



At least with a 'steady' problem, I felt that I could now isolate the origin. After reading the consensus, it appeared that the most common place for this error is in the connections behind the instrument cluster. I popped the cluster out without any real problems. All connectors looked clean and in place. I even removed the back of the cluster cover to inspect the circuit board. All looked good. Upon remounting the cluster (battery grounds had been removed when removing and installing), the problem still remained.



I then performed a cluster self-test (holding odometer reset on while turning ignition on). The cluster reported errors 900, 920, 921, 940, 950, and finally 999. After hitting the odometer reset, the self-test finished in the normal fashion... I'm guessing that this probably means that the cluster itself is good.



I then proceeded to check just about every other related connector (checking the status of the faults after each one in hopes of identifying the culprit) under the dashboard, in the engine compartment, and also checking all fuses.



After removing and reinstalling the cluster for about the 5th or 6th time (kept thinking that I had missed something and not truly confident in this self-aligning connection), everything went back to normal with the exception of:



4. "Check Engine" light on;

5. "ABS" light on;

and now, "brake" light is on as well.



I took the truck out for a spin and all seems well with the exception of the new lights that are on. I have know idea would could have repaired the other problems except for reinstalling the cluster over-and-over might have cleaned up some what appeared to be already very clean looking connectors. At least I have my gauges back and the "no bus" and "CCd" has extinguished and heated seats get toasty again. Toggleing the odometer gives the wonderful P1994 and P1993 again. I have NEVER seen any other vehicle (except for my wife's Durango) with such a worthless error detection system. Any other thoughts on this? Thanks again.

 

[dresslered]

One other thought is on a point that SSolderitch had mentioned was about the CCD bus going to the ABS. This is interesting as it appears that the remaining errors might be pointing in this direction. Also, I seem to remember that when the problem became permanent (dead gauges, etc. ), I had hit the brakes to make a stop light. Coincidence?

 

[JLandry]

The cluster reported errors 900, 920, 921, 940, 950, and finally 999.

David,



This is a tough one!



From what I'm reading in the Dodge service manual and diagnostic manuals, everything is pointing toward a communication bus failure at the ECM or PCM and nothing is wrong with the instrument cluster or any other module. Someone (a dealer) using a Chrysler DRBIII scan tool and the appropriate diagnostic manuals could quickly test the communications bus, and if necessary, isolate exactly where communications are being lost.



About all I can think of to do at this point would be to check the CCD bus wiring for shorts of open circuits between the ECM and PCM using a multimeter. If the wiring were to check out fine, then either the PCM or ECM would be suspect.



Do you have a Dodge service manual so you can figure out which wires and connectors to check?



John L.

 

[dresslered]

Thanks John,

I do have the manual and have been studying a lot lately. I really nead a DRBIII scan tool at this point. Unfortunately, in our area, the Dodge dealers were absolutely terrible prior to the closures. Went in once while the truck was under warrantee for a lift pump and the mechanic didn't even realize it was a diesel. I took the truck back and did the job myself.

 

[JLandry]

I do have the manual and have been studying a lot lately. I really nead a DRBIII scan tool at this point.

David,



Glad to hear you have the Dodge service manual... that makes this a whole lot easier.



The diagnostic procedures for DTC P1694 (No Bus Messages Received from Companion Module) indicate the communication problem originates with the ECM. The DTC comes from the PCM, and it's the PCM reporting it's not hearing from the ECM. The Didge diagnoctic procedures woud have you erase this DTC from the PCM, then cycle the ignition off and back on (without starting the engine) to see if it immediately returns. If it does, they'd have you troubleshoot the CCD bus wiring. If the wiring checked out OK, then you replace the ECM.



Here's how I would recommend you test the CCD bus wiring. See pages 8W-30-40 and 8W-30-41 in the service manual for the appropriate wiring diagrams:



1. Isolate the entire CCD bus wiring by disconnecting everything attached to it. This can be done by unplugging the following items:

ECM

PCM connector C3

Airbag Control Module

Radio

Overhead Console

Instrument Cluster

Central Timer Module connector C1

CAB (Controller Anti-Lock Brake)



Notes:



Make sure nothing is plugged into the ODBII port under the dash (like a code scanner).



Unplugging the ECM, PCM, Airbag Control Module, and CAB should be simple and straightforward, as they're all easy to reach.



The Central Timer Module is up under the dash, and to be honest, I'm not sure how accessible it is because I've never had the need to mess around with it. See chapter 8E in the service manual for diagrams of its location.



It's worth mentioning that the Airbag Control Module, Radio, and Overhead Console could all be disconnected together (from the rest of the modules on the CCD bus) by simply unplugging Joint Connector #7 under the dash. See figure 24 of chapter 8W-90 for a diagram. However, going this route would leave the portion of the CCD bus wiring between Joint Connector #7 and the aforementioned modules untested in the next steps.​

2. Using a multimeter, check for continuity between each of the following pins/sockets and a good ground on the vehicle. You shouldn't find any continuity. If you do, you have a short to ground somewhere which will need to be isolated and repaired. To be extra clear about this, the CCD bus wiring is NOT grounded anywhere to the vehicle or engine.

OBDII Connector pins 3 and 11

ECM pins 40 and 41

PCM connector C3 pins 28 and 30

Airbag Control Module pins 21 and 22

Radio pins 1 and 2

Overhead Console pins 2 and 8

Instrument Cluster pins 9 and 10

Central Timer Module connector C1 pins 16 and 17

CAB pins 3 and 10​

3. Check for continuity between the following combination of wiring harness pins/sockets (they're all connected together). This is the "ground" circuit of the CCD bus. Ideally the resistance should 5-10 Ohms or less between any two pins/sockets. If you discover an open circuit, then you have a break somewhere in the wiring which will have to be isolated and repaired. Diagrams of the pin/socket numbers for each connector can be found in chapter 8W-80 of the service manual.

OBDII Connector pin 11

ECM pin 40

PCM connector C3 pin 28

Airbag Control Module pin 22

Radio pin 2

Overhead Console pin 8

Instrument Cluster pin 9

Central Timer Module connector C1 pin 17

CAB pin 10​

4. Check for continuity between the following combination of pins/sockets (they're all connected together). This is the "positive" circuit of the CCD bus. Ideally the resistance should 5-10 Ohms or less between any two pins/sockets. If you discover an open circuit, then you have a break somewhere in the wiring which will have to be isolated and repaired.

OBDII Connector pin 3

ECM pin 41

PCM connector C3 pin 30

Airbag Control Module pin 21

Radio pin 1

Overhead Console pin 2

Instrument Cluster pin 10

Central Timer Module connector C1 pin 16

CAB pin 3​

Good luck,



John L.

 

[dresslered]

Thanks John, this looks like it is going to be so much fun! I kringe at the thought that this bus is associated with the Airbag Control Module.

 

[JLandry]

kringe at the thought that this bus is associated with the Airbag Control Module.

Fear not!



All you'll be doing is unplugging a connector and you won't be fooling around with the actual airbag circuits in any way.



The connector for the Airbag Control Module is under the plastic cover on the transmission hump under the dash. Easy access.



John L.

 

[dresslered]

"I kringe at the thought that this bus is associated with the Airbag Control Module. "



John,

I'm not worried about me igniting the airbag as I have been all through this truck. I'm worried about our lovely bus deciding to freak out again this time with the airbag!

 

[dresslered]

Hopefully, I can add some closure to this topic. After starting up the truck this morning, the final three indicator lights (check engine, ABS, and brake) extinguished themselves. All that I can think of is that reseating the instrument several times last weekend corrected the faulty connection, although I paid particular attention to pins 9 and 10 of the C1 connector (CCD BUS- and CCD BUS+) and saw nothing wrong with them. I even examined the cluster ciruit board and saw nothing wrong. After the problem was corrected, then perhaps it was only a matter of time (engine starts) that it took for the computer to reset the error. I would sure love to have a peak at Dodge's program code.



Looks like the Dodge Gods gave me an early Christmas present. Merry Christmas to you all and thanks for the help.



P. S. While on my test drive I noticed the fuel pressure is now fluctuating. Looks like I am now getting a sticking vane on the 5th lift pump. God, I love these trucks!

 

[JLandry]

P. S. While on my test drive I noticed the fuel pressure is now fluctuating. Looks like I am now getting a sticking vane on the 5th lift pump.

David,

I really hope the problem has disappeared for good, but taking all the DTC's and symptoms together... especially now with your report of fluctuating fuel pressure... I can't help but wonder if the ECM might be on the way out. Hopefully not, but be ready for it just in case.

Merry Christmas and a happy winter solstice to you!

John L.

 

[dresslered]

...hoping your wrong about the ECM

Thanks for the vote of confidence John.



When performing exhaustive searches on this topic (dead gauges), I found that a majority of the people isolated the problem to the back of the instrument cluster. I even exchanged emails with an old TDR friend John McIntyre on the other side of the pond who had this same exact problem. I'm sure hoping that this is it.



Regarding the transfer pump, the current one was proving to be the "Mother of All pumps" with over 50k miles on it. It's always held the highest pressure. The drop in pressure and fluctuations are exactly like I have seen with previous pumps. Not only that, but the truck has been sitting for awhile and we are experiencing some colder (by Kalifornia standards) than normal temperatures in the 30's. I'm not sure that the ECM could show this kind of behavior as the relay to the pump is either on or off. Fingers crossed and happy holidays to you. Thanks for your help.



David