Circuit Description
The PCM contains integrated Knock Sensor (KS) diagnostic circuitry. The PCM uses the circuitry to diagnose the KS sensors and related wiring. The PCM calculates an average voltage of each knock sensor's signals and takes instantaneous signal voltage readings. The PCM uses the instantaneous signal voltage readings to determine the state of the knock sensor circuitry. If the knock sensor system is operating normally, the PCM should monitor instantaneous KS signal voltage readings varying outside a voltage range above and below the calculated average voltage. If the PCM malfunctions in a manner which will not allow proper diagnosis of the KS circuit DTC 325 will set.
Conditions for Running the DTC
| • | No TP, VSS, CKP sensor, CMP sensor, MAF sensor, or ECT sensor DTCs are set. |
| • | Engine speed: |
| - | Manual Transaxle - engine speed is between 1000 and 3000 RPM. |
| - | Automatic Transaxle - engine speed is between 1000 and 4000 RPM. |
| • | Throttle angle: |
| - | Manual Transaxle - Throttle angle is greater than 15%. |
| - | Automatic Transaxle - Throttle angle is greater than 3%. |
| • | Engine load: |
| - | Manual Transaxle - engine load is greater than 45%. |
| - | Automatic Transaxle - engine load is greater than 20%. |
| • | Engine coolant temperature is greater than 75°C (167°F). |
| • | Maximum spark retard is less than 15 degrees. |
| • | System voltage is greater than 9 volts. |
Conditions for Setting the DTC
| • | The PCM detects a malfunction in the integrated knock sensor diagnostic circuitry which will not allow proper diagnosis of the knock sensor circuits. |
| • | The condition is present for 300 3X reference periods (100 crankshaft revolutions). |
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed. |
| • | The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed. |
| • | The 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. |
Diagnostic Aids
Check for the following conditions:
| • | Poor connection at the PCM or Knock Sensor 1. |
| Inspect knock sensor 1 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 Freeze Frame/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
Number(s) below refer to the step number(s) on the Diagnostic Table.
-
Ensures that the malfunction is present.
-
This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM isreplaced, the new PCM must be programmed.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform 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. Refer to Engine Noise Diagnosis in Engine Mechanical.
Does scan tool indicate this DTC failed this ignition? | -- | |||
3 |
Does the scan tool indicate this DTC failed this ignition? | -- | Go to Diagnostic Aids | |
|
Important:: The replacement PCM must be programmed. Go to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the replacement? | -- | -- | ||
5 |
Does the DTC reset? | -- | System OK |
