P0490

DTC P0490: EGR Valve (stepper motor) Circuit Malfunction (battery short) [California]

EGR Valve (Stepper Motor) Circuit <California> (Part 1):

EGR Valve (Stepper Motor) Circuit <California> (Part 2):

CIRCUIT OPERATION
- The EGR valve power is supplied from the MFI relay (terminal No. 2).
- The ECM (terminals No. 31, No. 32, No. 47, No. 48) drives the stepper motor by sequentially turning "ON" the power transistors in the ECM and providing ground to the EGR valve (terminal No. 1, No. 3, No. 4, No. 6).

TECHNICAL DESCRIPTION
The ECM checks whether a short circuit to the power supply exists or not by measuring the EGR valve (stepper motor) drive circuit voltage when the current is not flowing through the coil of the EGR valve (stepper motor).

DESCRIPTIONS OF MONITOR METHODS
When the EGR valve (stepper motor) drive circuit voltage is over the specified range, it is judged that a malfunction exists.

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)
- Exhaust gas recirculation (EGR) stepper motor monitor

Sensor (The sensor below is determined to be normal)
- Mass airflow 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
- Ignition switch is "ON" position.
- Battery positive voltage is between 10 and 16.5 volts.

Judgement Criterion
- When EGR valve is energized, the ECM voltage should be 6.7 volts or more for 1.4 seconds.

OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 3. OBD-II Drive Cycle

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

DIAGNOSIS

Required Special Tools:
- MB991958: Scan tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991910: Main Harness A

STEP 1. Check harness connector B-114 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 5.

STEP 2. Measure the EGR valve motor coil resistance.

1. Disconnect the EGR valve connector B-114.




2. Measure the resistance between EGR valve connector terminal No. 2 and either terminal No. 1 or terminal No. 3.

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. 4 or terminal No. 6

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 5.

STEP 3. Check harness connector B-108 at ECM for damage.

Q: Is the harness connector in good condition?

YES : Go to Step 4.

NO : Repair or replace it. Then go to Step 5.

STEP 4. Check for short circuit to power supply between EGR valve connector B-114 and ECM connector B-108.

a. EGR valve connector B-114 (terminal No. 1) and ECM connector B-108 (terminal No. 31).
b. EGR valve connector B-114 (terminal No. 3) and ECM connector B-108 (terminal No. 32).
c. EGR valve connector B-114 (terminal No. 4) and ECM connector B-108 (terminal No. 47).
d. EGR valve connector B-114 (terminal No. 6) and ECM connector B-108 (terminal No. 48).

Q: Is the harness wire in good condition?

YES : Replace the ECM. When the ECM is replaced, register the ID code. Then go to Step 5.

NO : Repair it. Then go to Step 5.

STEP 5. 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 3. OBD-II Drive Cycle
2. Check the diagnostic trouble code (DTC).

Q: Is DTC P0490 set?

YES : Retry the troubleshooting.

NO : The inspection is complete.