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ive checked everything i can think. the wiring seems to check out hardly any resistance. has power and ground where its supposed to yet the aldl wont communicate nor will the dash cluster. but everything else on the van works even the cruise so i know bcm is fine.
how do you test a serial bus? thats the last thing on my list and the wires test good on the bus? my scanner will communicate with the bcm but only with the key off.
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I would check all the fuses first, most problems like that are fuse related. Look for simple solutions before the complex ones.
Thanks for the tip Eric. i have gone so far as to remove All the fuses and test them with a digital multimeter. they all test good. all the fuses related to the dash and instrumentation have power with key on. With the ALDL. not communicating with my scanner with key on( will recognize the BCM with key OFF) i feel it could be a wiring/serial bus issue but my knowledge stops there. ive located the violet and white wire twisted pair that according to the wiring diagram is the serial bus responsible for instrumentation and the aldl. i tested the wires with all ends unhooked from computer bcm and the bulkhead connector and the resistance seems normal. .001 ohm same as if i touch my leads together. replaced the bcm as previous owner stated his mechanics diagnosis was and problem remains. What is my next step in diagnosing this?
You would need to figure out what type of network bus circuit you have. If one of the nodes goes bad, it can affect the other nodes via communication issues.
You could also refer to a FSM for diagnosis.
Keep us posted.
Well i dont really know alot about electronics beyond what i have done. So i dont know how to determine what type of network bus circut i have. im not sure what you mean by fsm field service manual?
If it were me I’d be getting my hands on the service procedure for no communication with the DLC. I’m certain the FSM has a write up on this procedure.
The issue has been determined to be a faulty ECM. The case had corroded severely and the corrosion overran the gel and got into the circuitry and caused the issue. A replacement ECM solved the issue. Thank for the help!!
The issue has been determined to be a faulty ECM. The case had corroded severely and the corrosion overran the gel and got into the circuitry and caused the issue. A replacement ECM solved the issue. Thank for the help!!
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