P0403

DTC P0403: Exhaust Gas Recirculation Control Circuit

EGR Valve Circuit (Part 1):

EGR Valve Circuit (Part 2):

CIRCUIT OPERATION
- The EGR valve power is supplied from the MFI relay (terminal No. 4).
- The PCM (terminals No. 124, No. 130, No. 136, No. 142) drives the stepper motor by sequentially turning "ON" the power transistors in the PCM and providing ground to the EGR valve (terminal No. 1, No. 3, No. 4, No. 6).

TECHNICAL DESCRIPTION
- To judge if there is open circuit in the EGR valve (stepper motor) drive circuit, PCM measure the surge voltage of the EGR valve motor coil.

DESCRIPTIONS OF MONITOR METHODS
Off-surge does not occur after stepper motor is operated on to off.

MONITOR EXECUTION
Continuous

MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)

Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
- EGR stepper motor monitor

Sensor (The sensor below is determined to be normal)
- Mass air flow sensor
- Engine coolant temperature sensor
- Intake air temperature sensor
- Barometric pressure sensor
- Accelerator pedal position sensor
- Manifold absolute pressure sensor

DTC SET CONDITIONS

Logic Flow Chart:

Check Conditions
- Battery positive voltage is higher than 10.3 volts.
- In a few seconds, just after ignition switch is turned to the "ON" position from the "LOCK"(OFF) position. (While EGR valve is being initialized.)

Judgement Criterion
- The EGR valve motor coil surge voltage (battery positive voltage +2 volts) is not detected for 3 seconds.

Check Condition
- Battery positive voltage is higher than 10.3 volts.

Judgement Criterion
- The EGR valve motor coil surge voltage (battery positive voltage +2 volts) is not detected for 30 seconds when the EGR valve is turned to "OFF" from "ON".

OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 25. OBD-II Drive Cycle

TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- EGR valve (stepper motor) failed.
- Open or shorted EGR valve (stepper motor) circuit, harness damage or connector damage.
- PCM failed.

DIAGNOSIS

STEP 1. Check harness connector B-105 at EGR valve for damage.

Q: Is the harness connector in good condition?

YES : Go to Step 2.

NO : Repair or replace it. Then go to Step 12.

STEP 2. Measure the EGR valve motor coil resistance.

1. Disconnect the EGR valve connector B-105.

2. Measure the resistance between EGR valve connector terminal No. 2 and either terminal No. 4 or terminal No. 6.

Standard value: 20 - 24 ohms [at 20 °C (68 °F)]

3. Measure the resistance between EGR valve connector terminal No. 5 and either terminal No. 1 or terminal No. 3.

Standard value: 20 - 24 ohms [at 20 °C (68 °F)]

Q: Is the measured resistance between 20 and 24 ohms [at 20 °C (68 °F)]?

YES : Go to Step 3.

NO : Replace the EGR valve. Then go to Step 12.

STEP 3. Measure the power supply voltage at EGR valve harness side connector B-105.

1. Disconnect the connector B-105 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.

3. Measure the voltage between terminal No. 2, No. 5 and ground.
- Voltage should be battery positive voltage.

4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is battery positive voltage (approximately 12 volts) present?

YES : Go to Step 5.

NO : Go to Step 4.

STEP 4. Check harness connector B-17X at MFI relay for damage.

Q: Is the harness connector in good condition?

YES : Repair harness wire between MFI relay connector B-17X (terminal No. 4) and EGR valve connector B-105 (terminal No. 2, No. 5) because of open circuit or short circuit to ground. Then go to Step 12.

NO : Repair or replace it. Then go to Step 12.

STEP 5. Measure the power supply voltage at PCM connector B-23 by using power plant ECU check harness special tool MB991923.

1. Disconnect all PCM connectors. Connect the power plant ECU check harness special tool MB991923 between the separated connectors.

2. Measure the voltage between terminal (No. 124, No. 130, No. 136, No. 142) and ground.
- The voltage should be between 5 and 8 volts for approximately 3 seconds when the Ignition switch is turned from the "LOCK" (OFF) position to the "ON" position.

3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the voltage normal?

YES : Go to Step 8.

NO : Go to Step 6.

STEP 6. Check harness connector B-23 at PCM for damage.

Q: Is the harness connector in good condition?

YES : Go to Step 7.

NO : Repair or replace it. Then go to Step 12.

STEP 7. Check for open circuit and short circuit to ground between EGR valve connector B-105 and PCM connector B-23.

Q: Is the harness connector in good condition?

YES : Go to Step 9.

NO : Repair or replace it. Then go to Step 12.

STEP 9. Check the EGR valve operation using special tool MB991658.

1. Remove the EGR valve.

2. Connect special tool MB991658 to the EGR valve. (All terminals should be connected.)
3. Use the jumper wires to connect terminal No. 5 of the EGR valve connector to the positive battery terminal.
4. Check to ensure that the motor operates when the terminal No. 1 and No. 3 of the EGR valve connector are respectively connected to the negative battery terminal using a jumper wire.
- Vibration should be present at each application of voltage to test clip combination.

5. Then, use jumper wires to connect the terminal No. 2 of the EGR valve connector to the positive battery terminal.
6. Check to ensure that the motor operates when terminal No. 4 and No. 6 of the EGR valve connector are respectively connected to the negative battery terminal using a jumper wire.
- Vibration should be present at each application of voltage to test clip combination.

7. Reinstall the EGR valve, using a new gasket, and tighten to the specified torque.

Tighten torque: 24 ± 3 N.m [17 ± 2 ft.lb]

Q: Is the EGR valve operating properly?

YES : Go to Step 10.

NO : Replace the EGR valve. Then go to Step 12.

STEP 10. Check for harness damage between MFI relay connector B-17X (terminal No. 4) and EGR valve connector B-105 (terminal No. 2, No. 5).

Q: Is the harness wire in good condition?

YES : Go to Step 11.

NO : Repair it. Then go to Step 12.

STEP 11. Check for harness damage between EGR valve connector B-105 and PCM connector B-23.

a. EGR valve connector B-105 (terminal No. 1) and PCM connector B-23 (terminal No. 142).
b. EGR valve connector B-105 (terminal No. 3) and PCM connector B-23 (terminal No. 136).
c. EGR valve connector B-105 (terminal No. 4) and PCM connector B-23 (terminal No. 130).
d. EGR valve connector B-105 (terminal No. 6) and PCM connector B-23 (terminal No. 124).

Q: Is the harness wire in good condition?

YES : Replace the PCM. When the PCM is replaced, register the encrypted code. Then go to Step 12.

NO : Repair it. Then go to Step 12.

STEP 12. Test the OBD-II drive cycle.

1. Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 25. OBD-II Drive Cycle
2. Check the diagnostic trouble code (DTC).

Q: Is DTC P0403 set?

YES : Retry the troubleshooting.

NO : The inspection is complete.