Chart B4 - BCM-To-Cps Power/Ground Problem

Fig 1: Chart B4, BCM-CPS Power/Ground Problem Schematic

You are at this chart because odometer, with key on, read all zeroes and courtesy lights did not turn on when switch was actuated. These symptoms indicate that BCM has lost power or ground with Central Power Supply (CPS).

NOTE: Test numbers refer to test numbers on diagnostic chart.

Checks for maximum blower speed with key on. Step will indicate whether BCM has lost logic ground circuit No. 801E with CPS.
This step determines if loss of logic ground is due to BCM, CPS or circuit No. 801E wire and terminals.
This step checks for 12 volts to BCM. If 12 volts is not present at BCM, fault is due to CPS or wiring.
This step checks for 7 volts to BCM, which has 2 individual inputs fed from CPS. Loss of both signals would result in system fault, otherwise fault is due to a bad CPS or BCM.

Fig 2: Flow Chart B4, BCM-CPS Power/Ground Problem

Fig 3: Flow Chart B4, BCM-CPS Power/Ground Problem