Diagnosis
Use the following scan tool parameters when diagnosing this circuit.
| • | The KS Noise Channel - This channel monitors the input signal from the knock sensor. This position should display YES when the knock is being detected and NO when no knock is being detected. |
| • | The KS Retard - This indicates how many degrees the PCM is retarding the spark timing. |
Circuit Description
The Knock Sensor (KS) detects abnormal vibration (spark knocking) in the engine. The sensor is mounted in the engine block near the cylinders. The sensor produces an AC output voltage which increases with the severity of the knock. The amplitude and frequency are dependent upon the knock level. This signal voltage is sent to the Powertrain Control Module (PCM) and the PCM will retard the electronic spark timing based on the signal being received to reduce the spark knock.
Diagnostic Aids
| • | This table does not check for an open knock sensor signal circuit. If the knock sensor signal circuit is open, a DTC P0325 will be set. |
| • | While observing the knock signal on the scan tool, there should be an indication that knock is present whenever detonation can be heard. Detonation is most likely to occur under high engine load conditions. |
Test Description
The number(s) below refer(s) to the number(s) on the diagnostic table.
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The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when the fault occurred. The scan tool stores this data for later reference. If a DTC P0325 is set, do not use this table.
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With the engine idling, there should be not be a knock signal present because detonation is not likely under a no load condition.
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If the engine has an internal problem which is creating a knock, the knock sensor may be responding to the mechanical noise.
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Tapping on the engine near the sensor simulates a knock. This step determines if the sensor can respond to an engine noise.
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The sensor will not produce any voltage unless a knock is present. Any voltage that is present at the sensor indicates that the sensor is malfunctioning.
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This step will determine if the reason that the knock sensor did not respond to the tapping was due to a malfunctioning sensor, KS module, or PCM.
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If the knock sensor signal circuit is routed too close to the ignition circuitry, the circuit may be picking up induced electrical noise causing a false knock signal.
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Reprogram the replacement PCM and reprogram the crankshaft position system variation learning procedure. Refer to the latest Techline information for PCM programming and the Powertrain Control Module (PCM) for the crankshaft position system variation learning procedure.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
Is a spark knock indicated? | -- | |||
Listen for an engine knock while increasing and decreasing the engine speed. Is an engine knock present? | -- | |||
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Caution: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury. Tap on the engine block near the knock sensor. Is spark knock indicated? | -- | |||
Is an AC voltage indicated? | -- | |||
Is an AC voltage indicated while tapping near the sensor? | -- | |||
Check the knock sensor signal circuit routing and repair the circuit routing as necessary. Was a repair necessary? | -- | |||
8 | Repair the basic engine problem. Is the action complete? | -- | -- | |
9 | Replace the knock sensor. Is the action complete? | -- | -- | |
Replace the PCM. Is the action complete? | -- | -- | ||
11 | Operate the vehicle within the conditions under which the original symptom was observed. Does the system now operate properly? | -- | System OK Refer to Diagnostic Aids |
