Circuit Description

WARNING: This page is about a different car, the 2002 Isuzu Rodeo Sport and 2002 Isuzu Rodeo. However, it is still accessible from the selected car via links, so may be relevant.

Knock Sensor (KS) is used to detect engine detonation. PCM retards engine spark timing based on KS signal. PCM supplies KS with a 5-volt signal which KS circuitry pulls down to about 1.3 volts when on knock is detected. Knock sensor produces an AC voltage signal that rides on the 1.3 volts DC. Signal amplitude and frequency are dependent on amount of knock being experienced.

PCM determines whether knock is occurring by comparing KS signal level with that of voltage level on noise channel. Noise channel allows PCM to reject a signal that appears to be a false signal, caused by normal engine noises. If PCM determines that an abnormally high noise still detects DTC P0327 will be set.

When DTC sets, PCM illuminates MIL on second trip after fault was detected. PCM will store conditions present when DTC was set as freeze frame data in the FAILURE RECORDS data. PCM will use a calculated spark retard value in order to minimize knock during conditions when knock is likely to occur. Calculated value will vary based on engine load and speed.

A history DTC P0327 will clear after 40 consecutive trip cycles during which diagnostic runs and fault is no longer recognized. DTC can be cleared with scan tool, or by disconnecting battery voltage feed to PCM.