P046C

DTC P046C

DTC DESCRIPTOR

DTC P046C
Exhaust Gas Recirculation (EGR) Position Sensor Performance

DIAGNOSTIC FAULT INFORMATION






IMPORTANT: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

TYPICAL SCAN TOOL DATA

EGR Position Sensor:

CIRCUIT/SYSTEM DESCRIPTION
The engine control module (ECM) uses the exhaust gas recirculation (EGR) position sensor to determine the position of the EGR valve. The ECM sends a reference voltage through the 5-volt reference circuit to the EGR position sensor. The ECM provides a voltage return path for the sensor through the low reference circuit. A variable voltage signal, based on the EGR valve position, is sent from the sensor to the ECM through the EGR position sensor signal circuit. The ECM compares the actual EGR position with the desired EGR position when the EGR valve is commanded open or closed.

CONDITIONS FOR RUNNING THE DTC
- DTCs P0401, P0402, P0403, P0642, or P0643 are not set.
- The EGR valve is actively being controlled.
- DTC P046C runs continuously when the above conditions have been met.

CONDITIONS FOR SETTING THE DTC
- The difference between the actual EGR position and the desired EGR position is more than 3 percent.
- The above condition is present for more than 5 seconds.

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 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.

CIRCUIT/SYSTEM VERIFICATION

IMPORTANT: If you cannot duplicate the condition, operate the vehicle within the conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

- If DTC P0403 is also set diagnose P0403 first.
- Observe that the EGR Position Variance parameter remains less than 4 percent difference while commanding the EGR valve to 10 percent.

CIRCUIT/SYSTEM TESTING
1. Test the following EGR circuits for resistance over 10 ohms.
- The 5-volt reference circuit
- The low reference circuit
- The motor low control circuit
- The motor high control circuit
- If any circuit is more than 10 ohms repair as necessary.
2. Disconnect the EGR valve connector, connect jumper wires between the EGR valve and the EGR valve harness connector for the 5-volt reference circuit, signal circuit, and the low reference circuit. Connect a test lamp between the EGR motor low control circuit and the EGR motor high control circuit on the EGR harness connector. Turn the ignition ON, the test lamp should flash ON and OFF.
- If the test lamp does not flash replace the ECM.
3. Remove the EGR valve and inspect for debris that will cause the EGR to stick and clean as necessary.
- If the EGR valve is sticking, has a weak spring, or is damaged and cannot be cleaned replace the EGR valve.

COMPONENT TESTING

IMPORTANT: Direct battery voltage to the EGR valve is not to exceed 5 seconds. Failure to perform the following procedure can result in inaccurate test results.

To test the resistance of the EGR motor perform the following test. Disconnect the EGR valve connector. Start the engine. Measure the ignition voltage at the battery and note this as the supply voltage. Connect a 5 amp fused jumper between the battery positive terminal and the high control circuit terminal on the EGR valve. Setup a DMM to measure amperage. Connect the DMM between the battery negative terminal and the low control circuit terminal on the EGR valve. Measure the amperage, note this as the current draw. Remove the DMM and the 5-amp jumper. To calculate the resistance of the EGR valve motor coil , divide the supply voltage by the current draw. Verify that the calculated resistance correlates to the appropriate EGR coil case temperature using the following table.
- 40°C (40°F) 1.42-2.88 ohms
- 25°C (77°F) 1.62-3.28 ohms
- 90°C (194°F) 1.75-3.66 ohms
- 150°C (302°F) 1.89-4.05 ohms
- If the calculated resistance is outside the specified range replace the EGR valve.


REPAIR INSTRUCTIONS
Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.

REPAIR VERIFICATION
- Exhaust Gas Recirculation (EGR) Valve Replacement
- Exhaust Gas Recirculation (EGR) System Cleaning
- Control Module References for replacement, setup, and programming.