Circuit Description
The Knock Sensor (KS) circuit consists of two knock sensors connected in parallel and a single wire to the VCM-A. Each knock sensor has a resistance value of about 8,200 ohms. The VCM-A supplies a 5 volt reference signal to the sensors when, because of the sensor resistance, it is cut in half to about 2.5 volts. When a knock occurs, a small AC voltage is generated by the knock sensors riding on top of the existing 2.5 volts. An AC voltage monitor in the VCM-A will detect this AC voltage and provide a signal to begin retarding spark until the knock diminishes.
Conditions for Setting the DTC
| • | No ECT Sensor DTCs are set. |
| • | No TP Sensor DTCs are set. |
| • | The engine run time is more than 2 minutes. |
| • | The VCM is in closed loop fuel control. |
| • | The ECT is more than 60°C. |
| • | The engine speed is more than 2200 RPM. |
| • | The TP sensor angle is more than 6%. |
| • | If the VCM determines that the filtered KS signal is out of range for more than 5 seconds, DTC P0326 sets. |
Action Taken When the DTC Sets
The VCM turns the MIL ON after 2 consecutive driving cycles with the fault active.
Conditions for Clearing the MIL/DTC
The VCM turns OFF the MIL after 3 consecutive driving trips without a fault condition present. A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (the coolant temperature has risen 22°C (40°F) from the start-up coolant temperature and the engine coolant temperature exceeds 71°C (160°F) during that same ignition cycle) or the scan tool clearing feature has been used.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 |
Important: Before clearing the DTCs, use the scan tool to record the Freeze Frame and the Failure Records for reference. This data will be lost when the Clear Info function is used. Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | |
2 |
Is the voltage for both sensor circuits at the specified value? | 5 volts | Go to Step 3 | Go to Step 4 |
3 | Measure the resistance between the knock sensor terminal and ground on both sensors. Is the resistance within the specified range for both sensors? | 600ohms -- 55,000ohms | Go to Step 5 | Go to Step 6 |
4 | Test circuit 496 for an open or short to ground. Repair the circuit if necessary. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9 |
5 | Check the knock sensor connector for a poor or intermittent connection. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 7 |
6 | Ensure that the knock sensors are installed properly. A knock sensor that has a poor ground to the engine block could cause this DTC to set. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 8 |
7 | Ensure that the KS wiring is routed properly and away from the secondary ignition wires. Also, ensure that the shielding around the KS circuits is properly installed. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9 |
8 | Replace the knock sensor that was out of range. Refer to Knock Sensor Replacement Did you complete the replacement? | -- | Go to Step 10 | -- |
9 | Replace the VCM. Refer to VCM Replacement/Programming . Did you complete the replacement? | -- | Go to Step 10 | -- |
10 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | Go to Step 11 | Go to Step 2 |
11 | With a scan tool, select Capture Info in order to observe the stored information. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to the applicable DTC table | System OK |
