DTC 52

Code Chart 52:

Knock Sensor Circuit:

CIRCUIT DESCRIPTION:

The knock sensor is used to detect engine detonation and the ECM will retard the electronic spark timing based on the signal being received. The circuitry within the knock sensor sends an AC voltage signal to the ECM based on the BLK wire and should measure about 2 to 300 mV AC. The amplitude and signal frequency are dependent upon the knock level. If the BLK wire becomes open or shorted to ground, the voltage will go below 200 mV. If this condition is met for about 5 seconds, a Code 52 will be stored.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. Code 52 will set when:

^ Coolant temperature is over 90°C (194°F).
^ MAT temperature is over 0°C (32°F).
^ High engine load based on MAF and rpm.
^ Voltage on BLK wire goes below 200 mV.
^ All conditions present for 5 seconds.
^ If and audible knock is heard from the engine, repair the internal engine problem as normally no knock should be detected at idle.

2. If tapping on the engine lift hook does not produce a knock signal, try tapping engine closer to sensor before proceeding.

3. This test checks the resistance of the knock sensor.