QuestionQUESTION: i have a 1993 dodge grand caravan 3.3.At times the speedo quits working and it will loose communication with scan tools. Also the engine cuts out. All of these symptoms are erratic and only last about half a second to a second. It doesn't matter if the engine is at operating temp or cool.
ANSWER: Hi Garry,
The 'CCD bus' vehicle communications system has some sort of a problem that is probably best diagnosed with a Chrysler Diagnostic Readout Box II (DRB II) (or equivalent) which can readout the memory of the system for specific fault codes. I have the '94 manual which is probably equally applicable to your '93. The components that share data are: Body control module, transmission control module, compass/mini-trip, instrument cluster, air bag module, powertrain (engine) engine control module. They are all connected together in a loop with a twisted pair of wires (white/black, violet/brown). With the engine running you could shake the harness at the plug to each of these devices to see whether you can induce the cut out behavior. There is only one plug for each device except the body control module in which the blue plug is the one to shake.
The most common failure I hear about is at the instrument cluster and it is usually due to a cold solder joint between the circuit board of the cluster and the socket into which the plug fits. That can be cured by reheating the solder joints between the socket pins and the board holes. Depending upon the effects of the flaky connection the entire bus can be impacted or just the specific module near the fault.
It is possible however that there are other sorts of gremlins having to do with the power supply for the bus and which would be revealed by the DRB II readout. That readout is performed via a 6-pin blue color "data link connector" under the dash next to the steering column.
I have the '93 van wiring diagrams as well should that be needed. There are other fault code readers that will also read the codes which are described as of the OBD-I fault code series. So you could check with several shops to see if they have such a reader and the necessary plug to mate with the data link connector (which has a rectangular array of 2 x 3 pins.
Ask for the fault codes numbers and/or names or specific "message" on the readout screen, what they would recommend doing and for how much. Then write me back with the results and we can compare that to the manual.
Roland
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QUESTION: Thanks, there are no codes that have been set. I have replaced the pcm, eatx and relays bcm and instrument cluster. I have also pulled the entire engine harness apart and checked for pinched, cut or any kind of damaged wires. then retaped it completely. The shop i took it to had a snap on modus scan tool.I have also checked fusible links.
AnswerHi Garry,
About all I can think of doing is attaching a digital voltmeter to the data link connector pin 3 and/or pin 4 and keep an eye on whether the bias voltage dips or pulses up at the moment that you notice the intermittent behavior.
Maybe try disconnecting the compass/mini-trip computer?
I assume the air bag light comes on when this happens as well? I recognize you replaced the other modules, but maybe you could find a used air bag module in a wrecking yard.
There isn't too much left of the CCD that you haven't replaced/checked. I would be pleased to learn what it was after you discover the solution.
Roland
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