Circuit Description
The exhaust gas recirculation (EGR) valve is vacuum operated. Vacuum for the EGR valve control system is supplied by a belt driven vacuum pump. The EGR valve vacuum control solenoid and the EGR valve vacuum vent solenoid work together to control the position of the EGR valve. The engine control module (ECM) monitors the EGR vacuum sensor signal to determine the amount of vacuum that is applied to the EGR valve. The ECM uses the mass air flow (MAF) sensor to calculate the amount of exhaust gas that is consumed by the engine. When the EGR valve is opened, the MAF rate will decrease. If the EGR vacuum sensor signal is higher than desired and the MAF rate is lower than expected, it is assumed that the EGR valve is not closing due to a vacuum problem and Diagnostic Trouble Code (DTC) P1404 sets.
Conditions for Running the DTC
| • | DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0405, P0406, P0489, P0490, P0500, P1639, P2142, P2144, P2144, and P2145 are not set. |
| • | The EGR valve vacuum control solenoid has been commanded to more than 70 percent. |
| • | The PCM is not in the Reduced Engine Power mode. |
| • | The BARO parameter is more than 72 kPa. |
| • | The Engine Speed parameter is between 610 - 820 RPM and is steady within 50 RPM for more than 3 seconds. |
| • | The ECT Sensor parameter is between 60° - 100°C (140°-212°F). |
| • | The Calculated Fuel Rate parameter is between 3 - 20 mm³. |
| • | The power take off (PTO) is disabled. (If equipted). |
| • | The IAT Sensor parameter is more than 0°C (32°F). |
| • | The APP Indicated Angle parameter is less than 1 percent. |
| • | The Ignition 1 Signal parameter is between 11-18 volts. |
| • | The Vehicle Speed Sensor parameter is less than 0.40 kPh (0.25 MPH). |
| • | The Engine Run Time parameter is more than 5 seconds. |
| • | All of the above conditions are met for more than 3 seconds. |
Conditions for Setting the DTC
| • | The ECM detects a higher than desired EGR vacuum sensor signal and a lower than expected MAF rate. |
| • | The above conditions are met for more than 4 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. |
Diagnostic Aids
Inspect for the following conditions:
| • | A stuck open EGR vacuum vent solenoid. |
| • | A stuck open EGR valve vacuum control solenoid. |
| • | Proper vacuum line connections. |
| • | A restriction in the exhaust system causing high back pressure. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The EGR vacuum vent solenoid is normally closed. When the EGR vacuum vent solenoid is closed, it will vent to atmosphere. Therefore it should not hold vacuum with this test.
-
The EGR valve vacuum control solenoid is normally closed. When vacuum is applied to the commanded open EGR vacuum vent solenoid it should hold vacuum. If the vacuum does not hold, then a stuck open EGR valve vacuum control solenoid is indicated.
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 | |||||
2 |
Did the DTC fail this ignition? | -- | Go to Step 3 | Go To Diagnostic Aids | ||||
|
Important: Mark all disconnected vacuum hoses for proper installation if necessary.
Does the vacuum hold steady? | -- | Go to Step 7 | Go to Step 4 | |||||
|
Important: Mark all disconnected vacuum hoses for proper installation if necessary.
Does the EGR vacuum control solenoid operate as described in the above test? | -- | Go to Step 5 | Go to Step 9 | |||||
5 |
Is the EGR Vacuum Sensor parameter within the specified value of the BARO parameter? | +/- 4 kPa | Go to Step 6 | Go to Step 8 | ||||
6 | Inspect for the following conditions:
Did you find and correct the condition? | -- | Go to Step 10 | Go to Diagnostic Aids | ||||
7 | Replace the EGR vacuum vent solenoid. Refer to Exhaust Gas Recirculation Valve Vent Solenoid Replacement . Did you complete the replacement? | -- | Go to Step 9 | -- | ||||
8 | Replace the EGR vacuum sensor. Refer to Exhaust Gas Recirculation Valve Vacuum Sensor Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- | ||||
9 | Replace the EGR valve vacuum control solenoid. Refer to . Did you complete the replacement? | -- | Go to Step 10 | -- | ||||
10 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 11 | ||||
11 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||
