Circuit Description
The body control module (BCM) monitors the ignition 1 voltage circuit 339,
the ignition 2 voltage circuit 743 and the engine run flag (ERF). The
ERF is a serial data message from the engine controller.
Conditions for Setting the DTC
| • | Ignition in the RUN position |
| • | Ignition in ACC circuit 743 shorted-to-ground or open |
| • | Engine run flag present (engine running) |
| • | All conditions for greater than 1 minute |
| • | No telltale illumination |
Diagnostic Aids
| • | A longer delay is required to set the diagnostic code for the ignition
ACC circuit low, than for the ignition 2 circuit low (1 minute instead
of 1 second). This timer has been added to avoid false diagnostic code setting,
if the vehicle has experienced an extremely long crank condition. Maximum recommended
crank time is 15 seconds to avoid damaging the starter. |
| • | Check for a poor connection at the BCM. Inspect the harness connectors
for backed-out terminals, improper terminal mating, broken connector locks, improperly
formed or damaged terminals and poor terminal-to-wire connection (crimped over the
wire insulation and not over the conductors). |
| • | Inspect the wiring harness for damage. Check for broken or chaffed insulation. |
| • | If the fault is suspected to be intermittent, wiggling the harness wiring
may help in locating the fault. |
