Circuit Description
The knock sensors are used to detect engine detonation, allowing the PCM to retard Ignition Control (IC) spark timing based on the KS signal being received. The knock sensors produce an AC signal which rides on a 5 volts DC signal supplied by the PCM. The signal amplitude and frequency is dependent upon the amount of knock being experienced.
The PCM determines whether knock is occurring by comparing the signal level on the KS circuit with the voltage level on the noise channel. The noise channel allows the PCM to reject any false knock signal by indicating the amount of normal engine mechanical noise present. Normal engine noise varies depending on engine speed and load. When the PCM determines that an abnormally high noise channel voltage level is being experienced, a DTC P0326 will set.
Conditions for Setting the DTC
| • | No active VSS, TP sensor, ECT sensor DTC(s) set. |
| • | Engine has been running for at least 10 seconds. |
| • | Engine coolant temperature is greater than 65°C (149°F). |
| • | Throttle angle is greater than 10%. |
| • | Engine speed is between 2200 RPM and 2500 RPM. |
| • | Noise channel voltage level above 4.8 volts is being indicated. |
Action Taken When the DTC Sets
| • | The PCM will not illuminate the malfunction indicator lamp (MIL). |
| • | The PCM will store conditions which were present when the DTC set as Failure Records data only. This information will not be stored as Freeze Frame data. |
Conditions for Clearing the MIL/DTC
| • | A History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using the scan tool Clear Info function. |
Diagnostic Aids
Check for the following conditions:
| • | Poor connection at PCM. Inspect knock sensor and PCM connectors for backed out terminals, broken locks, and improperly formed or damaged terminals. |
| • | Misrouted harness. Inspect the knock sensor harness to ensure that it is not routed too close to high voltage wires such as spark plug leads. |
Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.
Test Description
The numbers below refer to the step numbers on the Diagnostic Table.
-
Checks that the fault is present.
-
Checks for a false knock signal caused by a faulty knock sensor.
-
Checks that the knock sensors are capable of producing a correct AC signal.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On Board Diagnostic (OBD) System Check performed? | -- | ||
|
Important: : If an engine knock can be heard, repair the engine mechanical problem before proceeding with this diagnostic.
Does scan tool indicate DTC P0326 failed this ignition? | -- | |||
3 |
Does scan tool indicate DTC P0326 failed this ignition? | -- | Go to Diagnostic Aids | |
4 |
Does DMM indicate voltage near the specified value for knock sensor? | Approx. 5.0 volts | ||
5 | DMM on 400K ohms scale, measure the resistance of knock sensor by connecting the DMM between the sensor terminal and the engine block. Is resistance of knock sensor near the specified value? | 100K ohms | ||
Is any signal indicated on the DMM for knock sensor? | -- | |||
Is any signal indicated on the DMM while tapping on the engine lift bracket? | -- | |||
8 |
Was a problem found? | -- | ||
9 |
Was a problem found? | -- | ||
10 | Replace the affected knock sensor. Is the action complete? | -- | -- | |
11 |
Was a problem found? | -- | ||
12 |
Does the scan tool indicate DTC P0326 failed this ignition? | -- | Verify repair | |
13 | Replace the PCM. Important: : Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | |
14 |
Does scan tool indicate DTC P0326 failed this ignition? | -- | Repair complete. If a driveability symptom still exists, refer to Symptoms |
