GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Monte Carlo 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 DTC P0405

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 detect an excessively low EGR Position sensor signal voltage, this diagnostic trouble code (DTC) will set.

Conditions for Running the DTC

The system voltage is greater than 10 volts.

Conditions for Setting the DTC
    • The EGR Position sensor is less than 0.14 volts at any time.
    • The condition is present for more than 20 seconds.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle in which the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.
    • The PCM disables the EGR valve for the ignition cycle.

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 number below refers to the step number on the diagnostic table.

  1. This step verifies that the malfunction is present.

DTC P0405 - EGR Valve Pintle Position Circuit Low Voltage

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Important: If a DTC P1635 is set diagnose that DTC first.

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF
  3. With a scan tool, observe the EGR position sensor voltage parameter.

Does the scan tool indicate that the EGR position sensor voltage is less than the specified value?

0.14 V

Go to Step 4

Go to Step 3

3
  1. Observe the Freeze Frame/Failure Records data for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or as close to the Freeze Frame/Failure Records data that you observe.

Does the DTC fail this ignition?

--

Go to Step 4

Go to Intermittent Conditions

4
  1. Turn OFF the ignition.
  2. Disconnect the EGR valve connector.
  3. Connect a fused jumper wire between the 5-volt reference circuit of the EGR position sensor and the EGR valve position signal circuit of the EGR position sensor.
  4. Turn ON the ignition, with the engine OFF.
  5. With a scan tool , observe the EGR position sensor parameter.

Does the scan tool indicate that the EGR position sensor is near the specified value?

100%

Go to Step 10

Go to Step 5

5
  1. Disconnect the fused jumper wire.
  2. Probe the 5-volt reference circuit of the EGR position sensor with a test lamp connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 9

Go to Step 6

6

Test the 5-volt reference circuit of the EGR 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 15

Go to Step 7

7

Test all 5-volt reference circuits for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 8

8

With a DMM connected between the EGR position sensor 5-volt reference circuit and the EGR position sensor ground circuit, observe voltage while disconnecting all sensors, one at a time, that use a 5-volt reference signal. A change in voltage indicates the faulty component. Replace that component as necessary. Refer to the appropriate replacement procedure

Did you find and correct the condition?

--

Go to Step 15

Go to Step 11

9

Test the EGR valve position signal circuit for the following conditions:

    • A short to ground
    • High resistance
    • An open

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 11

10

Test the EGR valve position signal circuit for a short to the EGR solenoid high control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 12

11

Inspect for poor connections at the harness connector of the PCM . 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 15

Go to Step  14

12

Inspect for poor connections at the harness connector of 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  15

Go to Step 13

13

Replace the EGR valve. Refer to Exhaust Gas Recirculation Valve Replacement .

Did you complete the replacement?

--

Go to Step 15

--

14

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 15

--

15
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 16

Go to Step 2

16

With a scan tool, observe the stored information, Capture info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK