Chart B-9 BCM Problem

Chart B-9 - BCM Problem:

Wiring Diagram for Charts B-9 & B-10:

CHART B-9 - BCM PROBLEM

Circuit Description:

Since the BCM did not turn the courtesy lights on from the panel lamp switch, the BCM is not working, or the whole system lost its logic voltage 7V. The CPS must have and be providing power and ground as the CRT can display Radio function.


Test Description:

1. If the problem is that the BCM lost its ground the rest of the system would go to default modes and the Climate Control Fan would be on HI speed and the panel lights would be on full bright (backlighting). When the rest of the system is in default modes we know the BCM has 12 volts because it needs this much to establish defaults.


2. Verifying the integrity of the BCM grounds at the BCM will determine if the problem is wiring, including CPS connector and CPS or the BCM connector or BCM.


3. If the rest of the system did not default, verifying the integrity of the 12 volt circuit to the BCM, at the BCM, will determine if the fault is the 12 volt circuit or the CPS is not providing its logic voltage (7V).



4. If the 12 volt circuit to the BCM cheeked OK, verifying the integrity of the 7 volt logic circuits to the BCM, at the BCM, will determine if the problem is the CPS not providing the logic 7 volts or if the BCM connector, the BCM PROM, or the BCM is at fault.


5. If 7 volts was not present at the BCM, measuring these circuits again at the CPS will determine if the CPS is not supplying 7 volts or if these circuits are open.