Set Timing Mode

Set timing Circuit:

TEST CONDITION:

None.

FAILURE CONDITION:

BCM receives set timing bit form PCM/ECM.

ACTION TAKEN:

Display "Set Timing Mode" message on the CCDIC.

Set timing mode is a service aid designed into the fuel control system to allow spark advance to be disabled and engine timeing checked. If pin B of the ALDL connector is grounded, the PCM/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 99 or shorted sensor.

^ No Message - open in circuit 99, open in sensor, or open in circuit 1033.