Chart 2 Detonation Check

Diagnostic Chart:

Ignition Circuit:

CIRCUIT DESCRIPTION
The Detonation Check tests for proper Knock Sensor (KS) operation. Possible causes of detonation include KS, wiring, or Powertrain Control Module (PCM) faults, poor fuel quality or engine mechanical conditions. This chart requires J39200 voltmeter and J35616 jumper kit.

NOTES ON FAULT TREE
1. Tapping on engine block simulates the noise created by detonation.
2. The KS produces an Alternating Current (AC) voltage proportional in amplitude to the "loudness" of the knock condition.
3. The PCM uses the KS information to estimate the octane level of the fuel being used. The PCM selects a spark calibration for either 87, 90 or 93 octane.
4. Fuel with an octane level below 87 may cause detonation even with a properly operating engine. Engine mechanical problems such as low oil pressure, worn rod or main bearings or valve train problems may cause a knock condition.