HEI-Est-ESC System

The detonation sensor translates mechanical vibration into an AC voltage. This voltage typically runs on top of an DC reference voltage provided by the external detonation module or ECM for diagnostic purposes.

The detonation sensor translates every vibration into AC output voltage. The stronger the vibration, the higher the amplitude. Detonation creates the strongest output.

As noted earlier in the DESCRIPTION section of this article, the detonation sensor either communicates directly to the ECM or runs through an intermediary "detonation module".

In either case, the detonation module or ECM ignore all signals below a certain threshold as none-detonation noise, but retards timing for all signals above the threshold (detonation).

The ECM can retard timing directly, but the external detonation module must signal the ECM through a single-wire communications circuit. The ignition module leaves nine volts on the circuit to communicate no detonation, and grounds it to communicate detonation. The ECM responds appropriately.

If a retarded timing-type driveability problem is occurring, be sure to unplug this circuit to see if the problem goes away. If so, either the detonation module is falsely triggering a detonation condition, or the circuit is shorted to ground.

Beware of clearance in the valve train, or a loose trailer on a hitch, as they may create sufficient vibration to be considered as detonation.