One thing to note is that the gauges are all CCD bussed messages, however unlike many of the newer cars, the AS minivan receives the bus messages to the cluster from two different origin points. The OIL, TEMPERATURE, FUEL, and CHARGING gauges are all bussed message solely from the BCM. These circuits are hardwired to the BCM. In contrast, the tachometer and speedometer
are bussed messages from the PCM. So it is possible if the CCD bus wires were pushed out or cut from the PCM you will get a situation where ONLY the tachometer and speedometer will not operate. If the ccd wires were shorted or if you had a total bus failure (loss of bcm), then ALL THE GAUGES would become inoperative and would yield many CCD bus codes and/or NO RESPONSE messages.
If the car is not equipped with a tachometer, ONLY the speedometer will be inoperative. Most people assume the MIC, gauge(s), or BCM is at fault due this unique failure mode. When using the drb3 you should notice if the 'PCM IS INACTIVE' on the bus (goto bcm-system tests-pcm monitor). If the problem is intermittent then you may not see the error nor a code in the bcm. Use the manual to trace the ccd bus wiring connections and splices, for testing purposes you can jumper the ccd bus wires from the PCM back to the data link connector (valid ccd communication point), this will bypass any questionable connection points. 1991 was the first year the AS vans incorporated the gauges being bus dependant
can you have the codes read in the BCM at a repair shop or dealership?
It would be easier for you to test for the problem.
The data link connector is under the hood for the pcm.
Pins 3,4 should have 2.5 volts+-.3.
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