GM Service Manual Online
For 1990-2009 cars only

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. The EGR position sensor voltage varies depending on the position of the EGR valve. If the voltage on the signal circuit of the EGR valve position sensor is pulled higher than a calibrated value, DTC P0406 sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0406 Exhaust Gas Recirculation (EGR) Position Sensor Circuit High Voltage

Conditions for Running the DTC

    • The ignition is ON or the engine is operating.
    • DTC P0406 runs continuously once the above condition is met.

Conditions for Setting the DTC

The ECM detects that the EGR position voltage is more than 4.99 volts for more than 1 second.

Action Taken When the DTC Sets

    • The malfunction indicator lamp (MIL) will illuminate after 3 consecutive trips with a fail.
    • The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.

Conditions for Clearing the MIL/DTC

    • The MIL will turn OFF after 4 consecutive ignition cycles in which the diagnostic runs without a fault.
    • DTCs can be cleared by using the scan tool.
    • Disconnect the ECM battery feed for more than 10 seconds.

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

Go to Diagnostic System Check - Engine Controls

2

  1. Start the engine.
  2. Allow the engine to idle for 30 seconds.
  3. Observe the DTC Information with a scan tool.

Did DTC P0406 fail this ignition?

--

Go to Step 4

Go to Step 3

3

  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Operate the vehicle within the Conditions for Running the DTC.

Did the DTC fail this ignition?

--

Go to Step 4

Go to Intermittent Conditions

4

  1. Turn OFF the ignition.
  2. Disconnect the harness connector of the exhaust gas recirculation (EGR) valve.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage between the 5-volt reference circuit of the EGR valve position sensor and a good ground.

Is the voltage less than the specified value?

5.2 V

Go to Step 5

Go to Step 8

5

Important: Use a test lamp that measures between 25-30 ohms for this test.

Connect a test lamp between the 5-volt reference circuit and the low reference circuit of the EGR valve position sensor.

Does the test lamp illuminate?

--

Go to Step 6

Go to Step 11

6

Measure the voltage between the signal circuit of the EGR valve position sensor and a good ground.

Is the voltage less than the specified value?

5 V

Go to Step 7

Go to Step 10

7

  1. Connect a 3-ampere fused jumper wire between the signal circuit and the low reference circuit of the EGR valve position sensor.
  2. Observe the EGR Position Sensor parameter on the scan tool.

Is the parameter less than the specified value?

0.05 V

Go to Step 12

Go to Step 10

8

Test the 5-volt reference circuit of the following sensors for a short to voltage:

    • Manifold absolute pressure (MAP) sensor
    • Throttle position (TP) sensor
    • A/C pressure sensor
    • Fuel level sensor

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 9

9

Test the 5-volt reference circuit of the EGR valve position sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 13

10

Test the signal circuit of the EGR valve position sensor for one of the following conditions:

    • An open
    • High resistance
    • Short to voltage

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 13

11

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 16

Go to Step 13

12

Test for an intermittent and poor connection at the EGR valve. 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 16

Go to Step 14

13

Test for an intermittent and poor connection at the engine control module (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 16

Go to Step 15

14

Replace the EGR valve.

Did you complete the replacement?

--

Go to Step 16

--

15

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the replacement?

--

Go to Step 16

--

16

  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 17

17

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK