Circuit Description
The knock sensor (KS) system enables the powertrain control module (PCM) to control the ignition timing for the best possible performance while protecting the engine from potentially damaging levels of detonation. The KS is located on the intake side of the engine block. The KS produces an AC voltage signal that varies depending on the vibration level during engine operation. The PCM adjusts the spark timing based on the amplitude and frequency of the KS signal. The PCM receives the KS signal through a signal circuit. The KS ground is supplied by the PCM through a low reference circuit. The PCM uses the KS signal to calculate the average voltage and then assigns a voltage range value. The PCM should monitor a normal KS signal within the voltage range. If the PCM detects the KS signal outside of the voltage range, or the KS signal is not present, this DTC sets.
Conditions for Running the DTC
| • | DTCs P0117, P0118, P0122, or P0123 are not set. |
| • | The engine run time is more than 20 seconds. |
| • | The engine coolant temperature (ECT) sensor is more than 70°C (158°F). |
| • | The engine speed is between 1,800-6,400 RPM. |
| • | The manifold absolute pressure (MAP) is more than 55 kPa. |
| • | The ignition voltage is more than 10 volts. |
Conditions for Setting the DTC
The PCM detects that the KS signal is outside of the assigned voltage range, or the KS 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
| • | Inspect the KS for physical damage. A KS that is dropped or damaged may cause a DTC to set. |
| • | Inspect the KS for proper installation. A KS that is loose or over torqued may cause a DTC to set. The KS should be free of thread sealant. The KS mounting surface should be free of burrs, casting flash, and foreign material. |
| • | The KS must be clear of hoses, brackets, and engine electrical wiring. |
| • | For an intermittent condition, 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 that the malfunction is present.
-
This step tests for a KS that is shorted to ground.
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This step tests the KS for proper operation.
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This step tests for a short to voltage on the KS signal circuit and the KS low reference circuit.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connect End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
|
Important: If an engine mechanical noise can be heard, repair the condition before proceeding with this diagnostic. Refer to Symptoms - Engine Mechanical in Engine Mechanical -- 2.2L.
Does the DTC fail this ignition? | -- | Go to Step 3 | Go to Diagnostic Aids | |
Does the DMM display OL for both circuits? | -- | Go to Step 4 | Go to Step 8 | |
Important: Do not route the DMM leads near an ignition control device or an incorrect reading may result. Is the voltage below the first specified value at idle and above the second specified value at 3000 RPM? | 20 mV 80 mV | Go to Step 5 | Go to Step 8 | |
Is the voltage more than the specified value on any circuit? | 4.5 V | Go to Step 6 | Go to Step 7 | |
6 |
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 |
7 |
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 |
8 | Test for an intermittent and for a poor connection at the KS. 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 12 | Go to Step 10 |
9 | 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 12 | Go to Step 11 |
10 | Replace the KS. Refer to Knock Sensor Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
11 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
12 |
Does the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 13 |
13 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
