Circuit Description

Knock Sensor (KS) system is used to detect engine detonation. PCM will retard spark timing based on signals from KS module. KS produces an AC signal voltage that is sent to KS module. Amount of AC voltage produced is proportional to amount of knock.

When engine is operating, PCM will learn minimum and maximum frequency of noise engine produces. When PCM determines that this frequency is less than or more than expected amount, DTC will set.

DTC will set when following conditions are present:

• Engine operating for greater than 20 seconds.
• Engine coolant temperature greater than 158°F (70°C).
• Engine speed 1500-3500 RPM.
• Throttle angle greater than 0.5 percent.
• MAP is less than 60 kPa.
• PCM determines frequency is less than or greater than expected amount for less than 3 seconds.