Code 73 - Spark Retard Monitoring: Notes

When the need for ASR intervention is sensed by EBCM, it supplies battery voltage to circuit No. 1687 to request spark retard by ECM.

If EBCM senses an open, short to battery voltage or short to ground on circuit No. 1687, a Code 73 will be set.

1. Checks for short to battery voltage in circuit No. 1687.
2. Checks for short to ground in circuit No. 1687.
3. Measures resistance in circuit No. 1687 and internal ECM circuitry.
4. Checks for code reset after inspecting most of system.
5. Determines if problem found in step 3) is due to faulty ECM or an open in circuit No. 1687.