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 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 be within the assigned voltage range. This diagnostic trouble code will set if the KS signal is outside the assigned voltage range or not present.
Conditions for Running the DTC
| • | DTCs P0117, P0118, P0122, or P0123 are not set. |
| • | The ignition voltage is more than 10 volts. |
| • | The engine coolant temperature (ECT) sensor is more than 70°C (158°F). |
| • | The engine run time is more than 20 seconds. |
| • | The manifold absolute pressure (MAP) is more than 60 kPa. |
| • | The engine speed is between 1,800-6,400 RPM. |
Conditions for Setting the DTC
The knock sensor signal is outside the normal operating range or the knock sensor signal is 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 torqued correctly. Refer to Knock Sensor Replacement . |
| • | The mounting between the sensor and engine must be free of burrs, casting flash, and foreign material. |
| • | The KS head is clear from hoses, brackets, and engine wiring. |
| • | If the KS is dropped the knock sensor must be replaced. |
| • | For an intermittent condition, refer to Intermittent Conditions . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step verifies a condition is present.
-
This test is checking for continuity in the KS circuit. An out of limit on the DMM display is indicating an open in either the wiring or the PCM.
Step | Action | Values | 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 cycle? | -- | Go to Step 3 | Go to Diagnostic Aids | |
3 |
Does the DMM display a voltage above the specified value on either circuit? | 4.2 V | Go to Step 8 | Go to Step 4 |
Does the DMM display OL or infinite? | -- | Go to Step 6 | Go to Step 5 | |
5 |
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 7 |
6 | Test the signal circuit and the low reference circuit of the knock sensor for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 11 |
7 |
Does the voltage go from below the specified value at idle to above the specified value at wide open throttle (WOT)? | Below 25 mV to Above 60 mV | Go to Step 9 | Go to Step 10 |
8 | Repair the short to voltage in the signal circuit of the knock sensor or the low reference circuit of the knock sensor. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | Go to Step 13 |
9 | Repair the poor connection at the knock sensor harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 13 | -- |
10 | Replace the knock sensor. Refer to Knock Sensor Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- |
11 | Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 |
12 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- |
13 |
Does the DTC run and pass? | -- | Go to Step 14 | Go to Step 2 |
14 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
