Circuit Description
The engine control module (ECM) monitors the position of the exhaust gas recirculation (EGR) valve through the EGR valve position sensor. The EGR valve position sensor sends a feedback voltage on the signal circuit to the ECM. This voltage varies depending on the position of the EGR valve. The ECM interprets this voltage as the position of the EGR valve. When the ignition switch is turned ON, the ECM records the minimum value of the EGR valve position sensor which is the learned closed position. If the ECM detects a difference between the actual closed EGR position and the learned closed position of the EGR valve, DTC P0488 sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0488 Exhaust Gas Recirculation (EGR) Closed Position Performance
Conditions for Running the DTC
| • | DTCs P0112, P0113, P0405, P0406, and P0502 are not set. |
| • | The ambient air temperature is more than 3°C (37°F). |
| • | The engine is running. |
| • | The desired EGR position is 0 percent. |
| • | The ignition voltage is between 11.7-16 volts. |
| • | DTC P0488 runs continuously once the above conditions are met. |
Conditions for Setting the DTC
| • | The ECM detects a difference of more than 10 percent between the actual and the learned position of the EGR valve for more than 5 seconds. |
| • | The above condition must be detected 3 times. Each set of test samples are separated by more than 5 seconds with the desired EGR position being more than 30 percent. |
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 | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine 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 | |||||
2 |
Is the EGR Position Sensor parameter less than the specified value? | 1% | Go to Step 3 | Go to Step 4 | ||||
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Intermittent Conditions | ||||
4 |
Important: Use the J 35616-200 Test Lamp Kit for this test. If the J 35616-200 is not available, use a test lamp that measures between 25-30 ohms. Does the test lamp illuminate? | -- | Go to Step 6 | Go to Step 5 | ||||
5 | Connect a test lamp between the 5-volt reference circuit of the EGR valve position sensor and a good ground. Does the test lamp illuminate? | -- | Go to Step 9 | Go to Step 7 | ||||
6 | Connect a 3-amp fused jumper wire from the 5-volt reference circuit to the signal circuit of the EGR valve position sensor. Is the EGR Position Sensor parameter more than the specified value? | 99% | Go to Step 10 | Go to Step 8 | ||||
7 | Test the 5-volt reference circuit of the EGR valve position sensor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 11 | ||||
8 | Test the signal circuit of the EGR valve position sensor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 11 | ||||
9 | Test the low reference circuit of the EGR valve position sensor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 11 | ||||
10 | Test the EGR valve for the following conditions:
Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 12 | ||||
11 | Test for an intermittent and poor connection at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 13 | ||||
12 | Replace the EGR valve. Refer to Exhaust Gas Recirculation Valve Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- | ||||
13 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- | ||||
14 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 15 | ||||
15 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||
