DTC P1404 Exhaust Gas Recirculation (EGR) Closed Position Performance. Buick GL7 (Export) 2000

For 1990-2009 cars

### Circuit Description

The powertrain control module (PCM) monitors the exhaust gas recirculation (EGR) valve pintle position input to ensure that the valve responds properly to commands from the PCM. When the ignition switch is turned ON, the PCM learns the EGR closed valve pintle position. The PCM compares the learned EGR position to the actual EGR position when the EGR valve is commanded closed. If the actual EGR position indicates that the EGR valve is still open when the PCM is commanding the EGR valve closed, DTC P1404 will set.

### Conditions for Running the DTC

• | The IAT is more than -10°C (+14°F).

• | Desired EGR must equal 0.

• | The system voltage is between 10.0 and 18.0 volts.

### Conditions for Setting the DTC

• | The EGR feedback is 0.2 volts more than the EGR closed valve pintle position when the Desired EGR Position is commanded to 0 percent.

• | The above condition is present for more than 20 seconds.

### Action Taken When the DTC Sets

• | The PCM will illuminate the malfunction indicator lamp (MIL) during the first trip in which the diagnostic runs and fails.

• | If equipped with traction control, the PCM will command the EBTCM via the serial data circuit to turn OFF traction control and illuminate the TRACTION OFF lamp.

• | The PCM will store conditions which were present when the DTC set as Freeze Frame and Fail Records data.

### Diagnostic Aids

Inspect for the following conditions:

• | Any excessive deposits on the EGR valve pintle or seat. Remove the EGR valve and check for deposits that may interfere with the EGR valve pintle extending completely or cause the pintle to stick.

• | Any poor connections at the PCM or the EGR valve. Inspect the harness connectors for the following conditions:

- | Backed-out terminals

- | Improper mating

- | Broken locks

- | Improperly formed or damaged terminals

- | Poor terminal-to-wire connection

• | A damaged harness. Inspect the wiring harness for damage. If the wiring appears to be OK, connect a DMM and check the circuit continuity while moving the connectors and the wiring harnesses related to the EGR valve. A change in the DMM display indicates the location of the malfunction. Refer to the following procedures in Wiring Systems:

• | Testing for Continuity

• | Testing for Intermittent Conditions and Poor Connections

• | Repairing Connector Terminals

• | Connector Repairs

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. Verifies that the malfunction is present.

2. If DTC P1404 will only set under certain conditions, the malfunction may be intermittent; refer to DTC P1404 Diagnostic Aids. If an intermittent wiring problem is not present, inspect for a poor connection at the PCM or the EGR valve. If the connections are OK and DTC P1404 continues to set, replace the EGR valve.

3. This vehicle is equipped with a PCM which utilizes an electrically erasable programmable read-only memory (EEPROM). If the PCM is replaced, the new PCM must be programmed.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Important: : If DTC P0403 Exhaust Gas Recirculation (EGR) Solenoid Control Circuit are set, diagnose those DTCs first. With the engine idling, observe the Actual EGR Position display on the scan tool. Does the Actual EGR Position equal the specified value? | 0% | Go to Step 3 | Go to Step 5

3

1. Turn ON the ignition switch.
2. Select the scan tool EGR valve output control function.
3. Increment the EGR valve through all positions while comparing the Desired EGR Position to the Actual EGR Position.

Does the Desired EGR Position remain close to the Actual EGR Position at all commanded positions?

--

Go to Step 4

Go to Step 6

4

1. Review and record the scan tool Failure Records data.
2. Operate the vehicle within the Failure Records conditions.
3. Using a scan tool, monitor the Specific DTC info for DTC P1404 until the DTC P1404 test runs.

Does the scan tool indicate DTC P1404 failed this ignition?

--

Go to Step 5

Go to Diagnostic Aids

5

1. Disconnect the EGR valve.
2. Observe the Actual EGR Position on the scan tool.

Does the Actual EGR Position equal the specified value?

0%

Go to Step 6

Go to Step 7

6 | Probe the ground circuit of the EGR pintle position sensor at the EGR valve harness connector with a test lamp connected to B+ voltage. Does the test lamp illuminate? | -- | Go to Step 9 | Go to Step 8

7

1. Turn OFF the ignition switch.
2. Disconnect the PCM.
3. Turn ON the ignition switch.
4. Measure the voltage between the signal circuit of the EGR sensor and ground.

Is the voltage near the specified value?

0.0 V

Go to Step 12

Go to Step 11

8

1. Inspect the EGR sensor ground circuit for an open between the PCM and the EGR valve.
2. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a problem found?

--

Go to Step 15

Go to Step 13

9

1. Inspect for poor terminal connections at the EGR sensor.
2. If a problem is found, repair as necessary. Refer to Testing for Continuity , Testing for Intermittent Conditions and Poor Connections , Repairing Connector Terminals and Connector Repairs in Wiring Systems.

Was a problem found?

--

Go to Step 15

Go to Step 10

10

Replace the EGR valve. Refer to EGR Valve Replacement .

Notice: In order to prevent further damage if the EGR valve shows signs of excessive heat, check the exhaust system for blockage (possibly a plugged converter) using the procedure found on the restricted exhaust system check. If the exhaust system is restricted, repair the cause; one of which might be an injector which is open due to one of the following reasons:

• | Stuck

• | Grounded driver circuit

Check the oil for possible fuel contamination if a stuck open fuel injector is found.

Is the action complete?

--

Go to Step 15

--

11 | Locate and repair short to voltage in the signal circuit of the EGR sensor. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 15 | --

12

1. Test the following circuits:

• | The EGR valve pintle position signal circuit for a short to the 5 volt reference circuit.

• | The EGR valve pintle position signal circuit for a short to the EGR valve control circuit.

2. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a problem found?

--

Go to Step 15

Go to Step 14

13

1. Inspect the circuits related to the EGR valve for poor terminal connections at the PCM.
2. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a problem found?

--

Go to Step 15

Go to Step 14

14 | Important: : The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | Go to Step 15 | --

15

1. Review and record the scan tool Failure Records data.
2. Clear the DTCs.
3. Operate the vehicle within the Failure Records conditions.
4. Using a scan tool, monitor the Specific DTC info for DTC P1404.

Does the scan tool indicate DTC P1404 failed this ignition?

--

Go to Step 2

System OK