Circuit Description
The exhaust gas recirculation (EGR) vacuum sensor is used to monitor the amount of vacuum that is available to the EGR valve. A low reference circuit, 5 volt reference circuit and a vacuum sensor signal circuit are used to interface the ECM with the EGR vacuum sensor. If the EGR vacuum sensor signal voltage is above a calibrated value, DTC P0406 sets.
Conditions for Running the DTC
| • | DTC P1639 is not set. |
| • | The ignition is ON. |
| • | The Ignition 1 Signal parameter is between 11-18 volts. |
Conditions for Setting the DTC
| • | The EGR Vacuum Sensor parameter is more than 158 kPa. |
| • | The above conditions are met 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 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. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
Is DTC P1639 also set? | -- | Go to DTC P1639 | Go to Step 3 | |
3 |
Is the EGR Vacuum Sensor parameter more than the specified value? | 158 kPa | Go to Step 4 | Go to Intermittent Conditions |
4 |
Does the test lamp illuminate? | -- | Go to Step 6 | Go to Step 5 |
5 | Test the low reference circuit of the EGR vacuum sensor for high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 7 |
6 |
Does the scan tool indicate that the EGR Vacuum Sensor parameter is less than the specified value? | 18 kPa | Go to Step 8 | Go to Step 7 |
7 | Test the signal circuit of the EGR vacuum sensor for a short to voltage. Refer to Testing for a Short to Voltage and Wiring Repairs in Wiring Systems. 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 EGR vacuum sensor. 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 ECM. 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 EGR vacuum sensor. Refer to Exhaust Gas Recirculation Valve Vacuum Sensor Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
11 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
12 |
Did 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 | |
