GM Service Manual Online
For 1990-2009 cars only

Object Number: 293709  Size: MF
A/C Refrigerant Pressure Sensor, TP Sensor, Map Sensor, ECT Sensor, IAT sensor
Engine Controls Components
OBD II Symbol Description Notice
ESD Notice

Circuit Description

The PCM monitors the 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 closed valve pintle 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

System voltage is greater than 10 volts.

Conditions for Setting the DTC

    • EGR Feedback is 0.5 volt greater than the EGR Closed Valve Pintle Position when the Desired EGR Position is commanded to 0%
    • The above condition is present for longer than 20 seconds.

Action Taken When the DTC Sets

    • The PCM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
    • The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Freeze Frame and/or Failure Records.

The PCM will disable EGR for the ignition cycle.

Conditions for Clearing the MIL/DTC

    • The PCM turns the MIL Off after three consecutive drive trips that the diagnostic runs and does not fail.
    • A last test failed (current DTC) clears when the diagnostic runs and does not fail.
    • A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures.
    • Use a scan tool in order to clear the MIL/DTC.
    • Interrupting the PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Powertrain Control Module (PCM) Description , Clearing Diagnostic Trouble Codes.

Diagnostic Aids

Notice: Use the connector test adapter kit J 35616-A for any test that requires probing the following items:

   • The PCM harness connectors
   • The electrical center fuse/relay cavities
   • The component terminals
   • The component harness connector
Using this kit will prevent damage caused by the improper probing of connector terminals.

Check for 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.

If the problem is intermittent, refer to Intermittent Conditions .

Test Description

Number(s) below refer to the step number(s) 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 Diagnostic Aids. If an intermittent problem is suspected, check for poor connections at the PCM or the EGR valve. If the wiring and connections are OK and DTC P1404 continues to set, replace the EGR valve. Refer to Exhaust Gas Recirculation Valve Replacement .

  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.

Step

Action

Value(s)

Yes

No

1

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to the Powertrain On Board Diagnostic (OBD) System Check

2

Important: If DTC P0403 is set, diagnose DTC P0403 Exhaust Gas Recirculation (EGR) Solenoid Control Circuit first.

With the engine idling, observe Actual EGR Position display on the scan tool.

Is Actual EGR Position at the specified value?

0%

Go to Step 3

Go to Step 5

3

  1. Turn the engine off, then turn the key to On.
  2. Select the scan tool EGR valve output control function.
  3. Increment the EGR valve through all positions while comparing Desired EGR Position to Actual EGR Position.

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

--

Go to Step 4

Go to Step 6

4

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

Does the scan tool indicate DTC P1404 failed this ign?

--

Go to Step 5

Refer to Diagnostic Aids.

5

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

Is Actual EGR Position at the specified value?

0%

Go to Step 6

Go to Step 7

6

Probe the EGR pintle position sensor ground circuit at the EGR valve harness connector with test light J 35616-200 to B+.

Is the test light ON?

--

Go to Step 9

Go to Step 8

7

  1. Turn the key to Off.
  2. Disconnect the PCM.
  3. Turn the key to On.
  4. Measure voltage between the EGR valve pintle position signal circuit and ground using DMM J 39200 .

Is the measured voltage near the specified value?

0V

Go to Step 12

Go to Step 11

8

  1. Check the EGR pintle position sensor ground circuit for an open between the PCM and the EGR valve.
  2. If a problem is found, repair as necessary.

Was a problem found and corrected?

--

Go to Step 15

Go to Step 13

9

  1. Check for poor terminal connections at the EGR valve.
  2. If a problem is found, repair as necessary. Refer to Intermittents and Poor Connections Diagnosis in Electrical Diagnosis.

Was a problem found and corrected?

--

Go to Step 15

Go to Step 10

10

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

Notice: If the EGR valve shows signs of excessive heat, inspect 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. Inspect for an open injector caused by one or more of the following conditions:

   • Stuck
   • Grounded driver circuit
   • Possible faulty control module
If one of the above conditions is found, inspect the oil for possible fuel contamination.

Is the action complete?

--

Go to Step 15

--

11

Locate and repair short to voltage in the EGR pintle position signal circuit.

Is the action complete?

--

Go to Step 15

--

12

  1. Check for the following conditions:
  2. • 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.
  3. If a problem is found, repair as necessary.

Was a problem found and corrected?

--

Go to Step 15

Go to Step 14

13

  1. Check the circuits related to the EGR valve for poor terminal connections at the PCM.
  2. If a problem is found, repair as necessary.

Was a problem found and corrected?

--

Go to Step 15

Go to Step 14

14

Replace the PCM.

Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming .

Is the action complete?

--

Go to Step 15

--

15

  1. Clear DTCs with the scan tool.
  2. Turn the key to Off and wait 15 seconds
  3. Operate vehicle within the conditions that are required for this diagnostic to run. Refer to Conditions for Running the DTC.

Does the scan tool indicate that this test ran and passed?

--

Go to Step 16

Go to Step 2

16

Review Captured Info using the scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to the applicable DTC table

System OK