Circuit Description
The knock sensor (KS) produces an AC voltage at all engine speeds and loads. The powertrain control module (PCM) then adjusts the spark timing based on the amplitude and the frequency of the KS signal. The PCM uses the KS signal to calculate the average voltage. Then the PCM assigns a voltage value. The PCM checks the KS and related wiring by comparing the actual knock signal to the assigned voltage range. A normal KS signal should stay within the assigned voltage range. This diagnostic trouble code (DTC) will set if the KS signal is outside the assigned voltage range or not present.
Conditions for Running the DTC
| • | DTC P0117, P0118, P0121, P0122, P0123, P0125, P1114, P1115, P1121, or P1122 are not set. |
| • | The engine coolant temperature (ECT) is more than 60°C (140°F). |
| • | The engine run time is more than 10 seconds. |
| • | The manifold absolute pressure (MAP) is less than 44 kPa. |
| • | The engine speed is between 2,000-3,000 RPM. |
| • | The system voltage is more than 10 volts. |
Conditions for Setting the DTC
The knock signal is outside the assigned range or not present .
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
| • | The knock sensor must be correctly tightened to 25 N·m (19 lb ft). |
| • | The mounting between the sensor and engine must be free of burrs, casting flash, and foreign material. |
| • | Ensure the knock sensor head is clear from hoses, brackets, and engine wiring. |
| • | If an intermittent is suspected, refer to Intermittent Conditions . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step ensures the malfunction is present.
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This step ensures that the knock sensor is capable of detecting detonation and producing a signal.
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If the KS signal wire is shorted to ground or shorted to voltage the knock sensor may still produce a signal.
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If the KS low reference is shorted to ground or shorted to voltage the knock sensor may still produce a signal.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics | |||
1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | |
Important: If an engine knock can be heard, repair the engine mechanical condition before proceeding with this diagnostic. Does the DTC fail this ignition? | Go to Step 3 | Go to Intermittent Conditions | |
Does the DMM display a fluctuating frequency while tapping on the block? | Go to Step 6 | Go to Step 4 | |
4 |
Did you find and correct the condition? | Go to Step 11 | Go to Step 5 |
5 | Inspect for a poor connection at the knock sensor harness connector. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 9 |
Test for a short to ground and for a short to voltage in the KS signal circuit. Refer to Testing for Short to Ground and Testing for a Short to Voltage in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 7 | |
Test for a short to ground and a short to voltage in the KS low reference circuit. Refer to Testing for Short to Ground and Testing for a Short to Voltage in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 8 | |
8 | Inspect for a poor connection at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 10 |
9 | Replace the knock sensor. Refer to Knock Sensor Replacement . Did you complete the replacement? | Go to Step 11 | -- |
10 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | Go to Step 11 | -- |
11 |
Does the DTC run and pass? | Go to Step 12 | Go to Step 2 |
12 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | System OK | |
