For 1990-2009 cars

### Circuit Description

The KS system monitors both knock sensors in order to determine if pre-detonation is present. If the KS system determines that excessive knock (pre-detonation) is present, the PCM retards the spark timing based on the signals from the KS system. When knock is present, the KS system voltage input signal to the PCM goes low. The PCM then retards timing until no knock is present. When the KS system is malfunctioning, the KS circuit voltage going to the PCM goes low. The PCM interprets this low signal as spark knock.

### Conditions for Running the DTC

• | The engine speed is between 1,650 RPM and 3,000 RPM.

• | The MAP is greater than 49 kPa.

• | The engine coolant temperature is greater than 60°C (135°F).

• | The throttle angle is greater than 0.5%.

• | The engine run time is greater than 20 seconds.

### Conditions for Setting the DTC

• | A malfunction with the KS system or circuits within the PCM are faulty.

• | All above conditions present for 3.0 seconds.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

• | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records.

### Conditions for Clearing the MIL/DTC

• | The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

• | A last test failed, or current DTC, clears when the diagnostic runs and does not fail.

• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• | Use a scan tool in order to clear the MIL and the DTC.

### Diagnostic Aids

Important:

• | Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent contaminant intrusion into the PCM.

• | For any test that requires probing the PCM or component harness connectors, use the Connector Test Adapter Kit J 35616 . Using this kit prevents any damage to the harness connector terminals. Refer to Using Connector Test Adapters in Wiring Systems for procedures.

• | If the diagnostic test does not run, review the Conditions for Running the DTC.

• | Using the Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This will isolate when the DTC failed.

• | For an intermittent condition, refer to Symptoms .

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This DTC indicates an internal PCM fault.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Important:: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | Go to Step 3 | --
3 |

1. Select the Diagnostic Trouble Code (DTC) option and the Clear DTC option using the scan tool.
2. Idle the engine at the normal operating temperature.
3. Select the Diagnostic Trouble Code (DTC) option and the Specific DTC option, then enter the DTC number using the scan tool.
4. Operate vehicle within the Conditions for Running the DTC as specified in the supporting text, if applicable.

Does the scan tool indicate that this test ran and passed?

--

Go to Step 4

Go to Step 2

4 | Select the Capture Info option and the Review Info option using the scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to applicable DTC table | System OK