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 knock sensor and related wiring by comparing the actual knock signal to the assigned voltage range. A normal KS signal should stay outside the assigned voltage range. This diagnostic trouble code (DTC) will set if the KS signal is within the assigned voltage range or not present.
Conditions for Running the DTC
| • | DTCs P0101, P0102, P0103, P0121, P0122, P0123, P0335, P0340, P0385, P0502, P0503, P1114, P1115, P1121, P1122, or P1336 are not set. |
| • | The engine speed is between 1,000-3,000 RPM. |
| • | The throttle angle is more than 15 percent. |
| • | The engine load is more than 45 percent. |
| • | The engine coolant temperature is more than 65°C (149°F). |
| • | The maximum spark retard is less than 15 degrees. |
| • | The system voltage is more than 9 volts. |
| • | The engine run time is more than 30 seconds. |
Conditions for Setting the DTC
The PCM detects that the KS signal voltage remains within the calculated average voltage range.
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. |
Step | Action | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | |||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | |||||||
2 |
Important: If an engine knock can be heard, repair the engine mechanical condition before proceeding with this diagnostic.
Does the scan tool indicate that this diagnostic failed this ignition? | Go to Step 3 | Go to Intermittent Conditions | ||||||
3 |
Important: Do not tap on plastic engine components. Is any signal indicated on the DMM while tapping on the engine block near the knock sensor? | Go to Step 7 | Go to Step 4 | ||||||
4 | Test the KS signal circuit between the PCM and the knock sensor connector for the following:
Refer to Testing for Continuity , Testing for Short to Ground , Testing for a Short to Voltage in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 5 | ||||||
5 |
Did you find and correct the condition ? | Go to Step 9 | Go to Step 6 | ||||||
6 | Replace the knock sensor. Refer to Knock Sensor Replacement . Did you complete the replacement? | Go to Step 9 | -- | ||||||
7 |
Did you find and correct the condition? | Go to Step 9 | Go to Step 8 | ||||||
8 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | Go to Step 9 | -- | ||||||
9 |
Does the DTC run and pass? | Go to Step 10 | Go to Step 2 | ||||||
10 | With a scan tool, observe the stored information, Capture info. Does the scan tool display any DTCs that you have not diagnosed? | System OK | |||||||
