Service manual

90-898303 2-18

2000–2001 Models with CDM Ignition

The Detonation control system will only retard the timing approximately 1-2

degrees (uses same system as shift stabilizer on carburetor models).

The Detonation Control System consists of a detonation control sensor

located on the cylinder head and a detonation control module mounted on the

engine. The detonation control module uses the following wires:

• White/Blue – Connects to knock sensor, transmits knock signal to control

module.

• Green – Connects to #2 trigger. The trigger voltage signals the controller

to monitor combustion “noise” during a window of time.

• White/Black – Wire connects to the control module bias circuit.

• Gray/White – Connects to the ECM

• Purple – 12 Volt power supply.

DETONATION CONTROL SYSTEM FUNCTION

1) Combustion noise (or vibration) excites the piezoelectric circuit located

inside the detonation sensor, which transmits a voltage to the control

module.

2) When cylinder number two trigger generates a voltage pulse, it signals the

controller to look at a one millisecond window of sensor output, which it

retains as a reference level of combustion “background noise.”

3) When ”background noise” reaches a measurable value, usually between

2500 and 3500 RPM (it is dependent on load), the ignition timing is

advanced 3 degrees beyond what the mechanical timing is set at. Timing

advance is accomplished by lowering the bias voltage.

4) The controller continues to monitor sensor output. If the output exceeds a

predetermined threshold level over the “background noise” (which

indicates that knock is occurring) ignition timing is retarded by up to 1-2

degrees until the sensor output is reduced below the threshold level.

The detonation control system actually acts as an ignition advance module,

when knock occurs it takes away the advance. Ignition timing will not advance

if:

• Knock sensor fails.

• Blue/White wire becomes disconnected.

• Black wire has poor ground connection.

• Purple power wire becomes disconnected.

NOTE: Disconnected Gray/White wire will not affect ignition timing and will not

allow fuel enrichment. For further testing information, refer the Service

Manual.

Notes

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