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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1998 🢒 Cavalier (CNG) 🢒 DTC 🢒 DTC 31 EGR Valve Circuit

Object Number: 384481 Size: MF
Handling Electrostatic Discharge Sensitive Parts Notice
Handling Electrostatic Discharge Sensitive Parts Notice
Engine Controls Components
EVAP and EGR Controls (1 of 2)
OBDII Symbol Description Notice

Circuit Description

A linear exhaust gas recirculation (EGR) valve is used on this system. The linear EGR valve is designed to accurately supply exhaust gases to the engine without the use of the intake manifold vacuum. The EGR valve pintle position is monitored by the ECU in order to accurately calculate air flow of the engine at any given operating point. Control of the EGR valve is maintained by the PCM. EGR valve operation should not be affected by the ECU.

This is a type B DTC.

Conditions for Setting the DTC
    • The vehicle is in the CNG operation mode.
    • The ignition is ON.
    • The EGR valve position sensor signal is less than 0.088 volt, OR
    • The EGR valve position sensor signal is greater than 4.9 volts.

Action Taken When the DTC Sets

The ECU will set DTC 31 and turn ON the MIL after two consecutive driving cycles with the fault active.

Conditions for Clearing the MIL/DTC

The ECU turns the MIL OFF after three consecutive driving trips without a fault condition present. A DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 40°C (72°F) from the start-up coolant temperature and the engine coolant temperature exceeds 70°C (160°F) during that same ignition cycle) or the code clearing procedure has been used.

Diagnostic Aids

Always diagnose ANY PCM codes that are present before beginning this diagnostic procedure.

Inspect for the following conditions:

    • A poor connection, rubbed through wire insulation, or a wire that is broken inside the insulation may cause an intermittent problem.
    • Inspect the harness connectors for the following conditions:
       - Backed out terminals
       - Improper mating
       - Broken locks
       - Improperly formed or damaged terminals
       - A poor terminal to wire connection
       - Physical damage to the wiring harness

Refer to Intermittents in the powertrain diagnostics manual.

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. This step determines if DTC 31 is the result of low voltage or an open condition.

    2.

  2. This step isolates the ECU as the cause of a low circuit voltage problem.

    3.

  3. This step isolates the ECU as the cause of a high circuit voltage problem.

Step

Action

Value(s)

Yes

No

1

Was the AF Powertrain OBD System Check performed?

--

Go to Step 2

Go to Alternative Fuels (AF) Powertrain On Board (OBD) System Check

2

  1. Turn the key to the OFF position.
  2. Backprobe the EGR pintle position circuit at ECU connector C001 using a DVOM.
  3. Turn ON the ignition.

Does the DVOM display the EGR pintle position voltage less than the specified value?

0.24 V

Go to Step 4

Go to Step 3

3

Does the DVOM display the EGR pintle position voltage greater than the specified value?

4.9 V

Go to Step 6

Go to Diagnostic Aids

4

  1. Turn OFF the ignition.
  2. Disconnect ECU connector C001.
  3. Turn ON the ignition.

Does the DVOM display the EGR pintle position voltage less than the specified value?

0.24 V

Go to Step 5

Go to Step 10

5
  1. Turn OFF the ignition.
  2. Disconnect connector C018.
  3. Backprobe the EGR pintle position circuit in the engine harness side of connector C018, cavity B.
  4. Turn ON the ignition.

Does the DVOM display the EGR pintle position voltage less than the specified value?

0.09 V

Go to DTC P0405 EGR Valve Sensor Signal Low in Engine Controls - 2.2L in the J Platform Service Manual

Go to Step 9

6

  1. Turn OFF the ignition.
  2. Disconnect ECU connector C001.
  3. Turn ON the ignition.

Does the DVOM display the EGR pintle position voltage greater than the specified value?

4.9 V

Go to Step 7

Go to Step 10

7
  1. Turn OFF the ignition.
  2. Disconnect connector C018.
  3. Backprobe the EGR pintle position circuit in the engine harness side of connector C018, cavity B.
  4. Turn ON the ignition.

Does the DVOM display the EGR pintle position voltage greater than the specified value?

4.9 V

Go to DTC P0404 EGR Valve Open Pintle Position in Engine Controls - 2.2L in the J Platform Service Manual

Go to Step 8

8

Inspect for a short to voltage in the EGR pintle position circuit between connector C018 and C001.

Was a problem found?

--

Go to Step 11

Go to Diagnostic Aids

9

Inspect for an open or short to ground in the EGR pintle position circuit between connector C018 and C001.

Was a problem found?

--

Go to Step 11

Go to Diagnostic Aids

10

Inspect the ECU connector and the connector pins for damage or corrosion.

Was a problem found?

--

Go to Step 11

Go to Step 12

11

Repair the circuit as necessary. Refer to Wiring Repairs in Engine Controls - 2.2L in the J Platform Service Manual.

Is the action complete?

--

Go to Step 13

--

12

Replace the ECU. Refer to Engine Control Unit Replacement .

Is the action complete?

--

Go to Step 13

--

13
  1. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.
  2. Inspect to see if the MIL light still illuminates.

Did the diagnostic run and pass?

--

Go to Step 14

Go to Step 2

14

Are any ECU or PCM DTCs displayed that have not been diagnosed?

--

Go to the applicable DTC table

System OK