DTC P0405 Exhaust Gas Recirculation (EGR) Position Sensor Circuit Low Voltage. Buick GL7 (Export) 2000

For 1990-2009 cars

Refer to Engine Controls Schematics

#### Engine Data Sensors, MAF and EGR

.

### 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 and to detect a fault if the pintle position sensor circuit is open or shorted. If the PCM detects an excessively low EGR feedback signal voltage, DTC P0405 will set.

### Conditions for Running the DTC

• | The engine is running.

• | The system voltage is between 10 volts and 18 volts.

### Conditions for Setting the DTC

• | The EGR feedback is less than 0.35 volts at any time.

• | The 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 second consecutive trip in which the diagnostic test has been run and failed.

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

### Conditions for Clearing the MIL/DTC

• | The PCM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic has run and passed.

• | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

• | The DTC can be cleared by using a scan tool.

### Diagnostic Aids

• | Poor connection at the PCM or EGR valve--Inspect the harness connectors for:

- | Backed out terminals

- | Improper mating

- | Broken locks

- | Improperly formed or damaged terminals

- | Poor terminal to wire connection

• | Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

• | Damaged harness-- Inspect the wiring harness for damage. If the harness appears to be OK, connect a DMM and check the circuit continuity while moving connectors and wiring harnesses related to the EGR valve. A change in the DMM display will indicate the location of the malfunction. Refer to Wiring Repairs in Wiring Systems.

### Test Description

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

1. Verifies that the malfunction is present.

2. If DTC P0405 will only set under certain conditions, the malfunction may be intermittent; refer to Diagnostic Aids. If an intermittent wiring problem is not present, check for a poor connection at the PCM or the EGR valve.

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

#### DTC P0405 - EGR Valve Pintle Position Circuit Low Voltage

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: Go to DTC P1635 if it sets while the engine is running.

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 Actual EGR Position.

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

--

Go to Step 3

Go to Step 4

3

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 Specific DTC info for DTC P0405.

Does the scan tool indicate DTC P0405 failed this ignition?

--

Go to Step 4

Go to Diagnostic Aids

4

1. Disconnect the EGR valve electrical connector.
2. Connect a DMM to measure voltage between the EGR pintle position sensor ground circuit and the 5 volt reference A circuit at the EGR valve connector.

Is the voltage at the specified value?

5.0 V

Go to Step 5

Go to Step 9

5 | Probe the EGR valve pintle position circuit at the EGR valve harness connector with a test lamp connected to battery positive voltage. Is the test lamp on? | -- | Go to Step 8 | Go to Step 6

6

1. Connect a jumper between the 5 volt reference A circuit and the pintle position circuit at the EGR valve connector.
2. Observe the Actual EGR Position on the scan tool.

Is the Actual EGR Position at the specified value?

100%

Go to Step 13

Go to Step 7

7

1. Turn OFF the ignition switch.
2. Disconnect the PCM.
3. Check for an open in the EGR valve pintle position circuit.
4. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a problem found?

--

Go to Step 19

Go to Step 17

8

1. Turn OFF the ignition switch.
2. Disconnect the PCM.
3. Probe the EGR valve pintle position circuit with a test lamp to battery positive voltage.

Is the test lamp on?

--

Go to Step 12

Go to Step 15

9 | Probe the 5 volt reference A circuit with a test lamp to battery positive voltage. Is the test lamp on? | -- | Go to Step 10 | Go to Step 11

10

1. Turn OFF the ignition switch.
2. Disconnect the PCM.
3. Probe the 5 volt reference A circuit with a test lamp to battery positive voltage.

Is the test lamp on?

--

Go to Step 16

Go to Step 18

11

1. Test for an open in the 5 volt reference A circuit 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 19

Go to Step 17

12 | Locate and correct the short to ground in the EGR valve pintle position circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 19 | --

13

1. Inspect for the following conditions:

• | Poor terminal connections at the EGR valve.

• | The EGR pintle position signal circuit shorted to the EGR valve control circuit.

2. If a problem is found, repair as necessary. Refer to Testing for Continuity , Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems.

Was a problem found?

--

Go to Step 19

Go to Step 14

14

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.

Replace the EGR valve.

Is the action complete?

--

Go to Step 19

--

15

1. Test the EGR valve pintle position circuit for a short to the sensor ground circuit.
2. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a problem found?

--

Go to Step 19

Go to Step 18

16 | Locate and repair short to ground in the 5 volt reference A circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 19 | --

17

1. Test the circuits related to the EGR valve for a poor terminal connection at the PCM.
2. If a problem is found, repair as necessary. Refer to Testing for Continuity and Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Was a problem found?

--

Go to Step 19

Go to Step 18

18 | Important: : The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | Go to Step 19 | --

19

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 Specific DTC info for DTC P0405.

Does the scan tool indicate DTC P0405 failed this ignition?

--

Go to Step 2

System OK