For 1990-2009 cars

Table 1: | EGR Valve Terminal (Pin) Identification

EGR Valve and EVAP Controls
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The exhaust gas recirculation (EGR) system controls the formation of oxides of nitrogen (NOx) emissions by recirculating the exhaust gases into the combustion chamber. The EGR valve is a stepper motor design. The stepper motor moves a spring loaded plunger that controls the flow of exhaust gases into the intake manifold. The plunger movement is controlled by the powertrain control module (PCM). By turning the stepper motor in different directions, the PCM controls the opening of the exhaust gas passage to the intake manifold. The stepper motor has 4 coil windings that control the motor movement. The DTC P0403 diagnostic monitors the electrical circuits of the 4 coils.

### Conditions for Setting the DTC

The voltage observed by the PCM on the EGR valve coil control circuits is not within the expected values when the ignition is On.

OR:

The voltage observed by the PCM on the EGR valve coil control circuits is not within the expected values when the engine is running and the PCM requests the EGR valve On.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with the fault active.

• | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.

### Conditions for Clearing the MIL/DTC

• | The MIL turns off after 3 consecutively passing trips without a fault present.

• | A Hhistory DTC clears after 40 consecutive warm-up cycles without a fault.

• | Perform the scan tool Clear DTC Information function in order to clear the DTC.

### Diagnostic Aids

A normal engine operating temperature is specified as 80°C (176°F) or more.

Check for any of the following conditions:

• | An incorrect PCM can cause DTC P0403 to set. Verify that the correct PCM is installed in the vehicle as required for proper emission certification.

• | A faulty electrical connection at the PCM.

An intermittent malfunction may be caused by a fault in the EGR control system electrical circuits. Inspect the wiring harness and the components for any of the following conditions:

• | Any backed-out terminals

• | Any improper mating of terminals

• | Any broken electrical connector locks

• | Any improperly formed or damaged terminals

• | Any faulty terminal-to-wire connections

• | Any physical damage to the wiring harness

• | A broken wire inside the insulation

• | Any corrosion of the electrical connections, the splices, or the terminals

If a DTC P0403 is intermittent, driving the vehicle under the following conditions can verify whether the fault is present. Perform the scan tool Clear DTC Information function. Road test the vehicle while monitoring the DTC P0403 diagnostic on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0403 appears in the Not Ran Since Code Cleared list, the P0403 diagnostic has not yet run. When the DTC P0403 does not appear in the Not Ran Since Code Cleared list, the P0403 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the P0403 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status in order to determine the outcome of the diagnostic test involved.

If a DTC P0403 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC was first set.

Use the following table in order to locate the correct terminals to test during diagnosis. The table layout corresponds to the pin location of the EGR valve electrical terminals.

#### EGR Valve Terminal (Pin) Identification

Connector Lock Tab
Pin 3 | Pin 2 | Pin 1
Pin 6 | Pin 5 | Pin 4

### Test Description

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

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and to store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. This step checks the ignition positive voltage supply to the EGR coils.

3. This step tests the operation of the EGR valve. If the EGR valve responds to commands from the scan tool and the engine reacts to the valve opening, the system is operating normally at this time.

4. This step determines which EGR coil control circuits may be at fault. If a DTC P0403 resets within 1 minute, the circuits referred to in Step 8 or the PCM are at fault. If DTC P0403 DOES NOT reset within 1 minute, the circuits referred to in Step 6 or the PCM are at fault.

Step | Action | Value(s) | 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 |

1. Disconnect the EGR valve electrical connector.
2. Turn ON the ignition, leaving the engine off.
3. Connect a test lamp between the harness side of terminal 2 and ground.
4. Connect a test lamp between the harness side of terminal 5 and ground.

Does the test lamp illuminate on both circuits?

--

Go to Step 3

Go to Step 7

3 |

1. Use a digital multimeter (DMM) to measure the following EGR valve coil windings for the specified value of resistance. Refer to the EGR Valve Terminal Identification table in Diagnostic Aids.

• | Between pin 1 and pin 2

• | Between pin 2 and pin 3

• | Between pin 5 and pin 6

• | Between pin 4 and pin 5

2. Measure the resistance between pin 2 and EGR valve assembly, and between pin 5 and the EGR assembly. The resistance should be infinite.

Does the EGR valve pass all the resistance tests?

20-24 ohms at 20°C (68°F)

Go to Step 4

Go to Step 9

4 |

1. Connect the EGR valve electrical connector.
2. Install a scan tool.
3. Start the engine.
4. Operate the engine until the engine reaches a normal operating temperature.
5. Perform the scan tool Clear DTC Information function.
6. Using the scan tool, gradually command the EGR valve open to 100 percent.

Does the engine run rough or stall?

--

Go to Diagnostic Aids

Go to Step 5

5 |

1. Perform the scan tool Clear DTC Information function.
2. Start the engine.
3. Operate the engine for 1 minute or until the malfunction indicator lamp (MIL) illuminates.
4. Check for DTCs.

Is DTC P0403 set?

--

Go to Step 8

Go to Step 11

6 |

1. Test the EGR coil control circuits C4-14 and C4-15 for an open or a short circuit.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 11

Go to Step 10

7 | Repair the open in the ignition positive voltage circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 11 | --
8 |

1. Test the EGR coil control circuits C4-13 and C4-16 for an open or a short circuit.
2. Test the EGR coil control circuit C4-15 and circuit C4-14 for a short to ground.
3. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 11

Go to Step 10

9 | Replace the EGR valve. Refer to Exhaust Gas Recirculation Valve Replacement . Is the action complete? | -- | Go to Step 11 | --
10 | Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | Go to Step 11 | --
11 |

1. Perform the scan tool Clear DTC Information function and road test the vehicle within the Freeze Frame conditions that set the DTC.
2. Review the scan tool data and check for DTCs. The repair is complete if no DTCs are stored.

Are any DTCs displayed on the scan tool?

--

Go to Diagnostic Trouble Code (DTC) List

System OK