AutoFocus: Intermittent cluster trouble with the Dodge Caliber

Oct. 19, 2010

I received a call on a 2008 Dodge Caliber with an intermittent loss of the instrument cluster (IC) gauges and the warning lights would come on. The symptoms would only occur when the vehicle was actually driven. I asked the technician to check for codes in all of the modules.

He called me back with the following list of stored codes:

* U0019 -- CAN B bus, stored in the occupant restraint controller (ORC);

* U0020 -- CAN B bus off performance, stored in the radio;

* U0021 -- CAN B positive bus circuit open, stored in the totally integrated power module (TIPM);

* U0024 -- CAN B negative open, stored in the TIPM;

* U0025 -- CAN B negative circuit low, stored in the TIPM;

* U0141 -- Lost communication with the cabin compartment node (CCN);

* U0168 -- Lost communication with ORC, stored in the TIPM;

* U0195 -- Lost communication with satellite digital audio receiver (SDAR).

I asked the technician to clear all codes in all of the modules and test drive the vehicle to see if any codes reset. He called back to say all of the codes had reset, the original symptoms had shown up with the IC gauges not operating and the warning lights coming on, but then the IC gauges started working again. Since this appeared to be an intermittent CAN B bus failure, I checked for any service bulletins or flash updates but found none.

I gave him the location of all of the modules and instructed him to monitor the bus bias voltage. Normal voltage should be 4.5 volts on the white/light blue CAN B negative wire

and 0.5 volt on the white/orange CAN B positive wire. The technician saw the CAN B negative drop from 4.5 volts to 1.5 volts when the symptoms reappeared and the codes reset.

Because CAN B is not fault tolerant like CAN C, this would shut down the entire CAN B bus, resulting in the symptoms and the multiple codes setting.

Next, I instructed the technician to start disconnecting the modules on the CAN B bus, one at a time, while still monitoring the bus bias voltage, to see if just that module

code reset (or multiple codes) and if the symptoms came back in the other modules. The possible modules on the CAN B bus are the TIPM, SDAR, CCN, ORC, radio, radio amplifier, traffic information receiver module (TIRM), hands free module (HFM), and the wireless control module (WCM).

The technician reported that every time he disconnected a module and drove the vehicle, when the symptoms reappeared, he had the same results: the CAN B negative would drop to 1.5 volts and the multiple codes would set in all of the other different modules left on the bus. The TIPM couldn’t be disconnected as then the vehicle wouldn’t start or run.

My next suggestion was to: 1) cut the CAN B negative wire at the TIPM and the WCM; 2) run a new wire outside of the harness between the TIPM and the WCM modules; 3) start the vehicle and disconnect the wire at the WCM; and 4) monitor the bus voltage on the new wire that is currently run outside of the wiring harness to see if the symptoms reappeared when driving the vehicle.

When he called back, he said that the symptoms reappeared, so we were basically down to a bad TIPM. I had him check the connectors and any signs of terminal push outs or corrosion, and to check the terminal to pin fit. If it was all OK, I suggested he replace the TIPM.

Two weeks later, the technician called back to tell me that while he was disconnecting the TIPM, he noticed corrosion on the terminals and surrounding area of the plug-ins. He attempted to clean the TIPM, but the symptoms still appeared when driving. So he replaced the TIPM and confirmed that solved the problem.