Chart B1 - Odometer Power/Ground Problem

An incorrect odometer reading can be caused by problems relating to power and ground circuits not only in Instrument Panel Cluster (IPC), but those of other components within the computer network, the computer wake-up signals, the vacuum fluorescent power supply, the odometer mileage memory chip (EEPROM) contained in BCM, or by data link between computer components.

1. If no codes are set in diagnostic memory, observe state of odometer reading with headlight switch and twilight sentinel switch in the "OFF" position. This is important because these signals can wake-up the BCM and otherwise cause a misdiagnosis of a malfunctioning primary circuit.
2. When odometer reads all zeros, actuating the interior courtesy light switch helps to isolate exact cause of problem. This symptom is caused by a failure in computer system other than the IPC. Further isolation of this fault is diagnosed in CHARTS B2, B3 and B4.
3. When odometer is blank or reads all 8's, actuating headlight switch will help to isolate cause of problem. If odometer reads all zeros, cause of problem is due to a faulty "ISO IGN-3" feed circuit to BCM (open or shorted to ground) or BCM itself. If odometer is blank or reads all 8's, cause is due to one of several other problems within computer network.
4. Cycling the high beam or headlight dimmer switch will help to further isolate cause of problem. If high beams cycle, problem is related to IPC itself, IPC ground circuit, vacuum flourescent power supply circuit or components related to these circuits. Further fault diagnosis is contained in CHART B5.
5. If high beams did not cycle when dimmer switch was actuated, turning on courtesy lights switch will help to further isolate system problem. If courtesy lights turn on, problem is related to IPC itself, the CPS-to-IPC logic circuits ground, the 12-volt power circuits from CPS to IPC, or the CPS itself. Further problem isolation is contained in CHART B6.
6. If courtesy lights did not turn on when switch was actuated, several other causes for problem can be isolated by following CHART B7 and CHART B8, depending on whether the lights on chime sounds when test is run.