"Set Timing Mode" Message

TEST CONDITION(S)
None

FAILURE CONDITION(S)
1) BCM receives set timing bit from ECM.

ACTION TAKEN
1) Display "Set Timing Mode" message on Computer Control Driver Information Center (CCDIC).

DESCRIPTION
Set timing mode is a service aid designed into the fuel control system to allow spark advance to be disabled and engine timing checked. If pin B of the ALDL connector is grounded, the ECM will sense a ground on circuit 462 and enter set timing mode as long as the engine is running, the transmission is in park or neutral, and the engine RPM is below 900. When these conditions are met, the ECM will indicate this to the BCM over the UART data line and the BCM will send the "Set Timing Mode" message to the CCDIC.

DIAGNOSIS
Condition Possible Causes
Erroneous Message short to ground on circuit 462
No Message open in circuit 462 or bad connection at ECM pin 3E12