P0446

DTC P0446: Evaporative Emission Control System Vent Control Circuit

CIRCUIT OPERATION

- The evaporative emission ventilation solenoid power is supplied from the MFI relay (terminal No. 4).
- The ECM [M/T] or the PCM [A/T] controls the evaporative emission ventilation solenoid ground by turning the power transistor in the ECM [M/T] or the PCM [A/T] ON and OFF.

TECHNICAL DESCRIPTION

- To judge if there is open circuit in the evaporative emission ventilation solenoid drive circuit, ECM [M/T] or PCM [A/T] measures the surge voltage of the evaporative emission ventilation solenoid coil.
- The ECM [M/T] or the PCM [A/T] drives the evaporative emission ventilation solenoid. After the solenoid is turned off, the ECM [M/T] or the PCM [A/T] will check if the solenoid coil produces a surge voltage (battery positive voltage + 2 volts).

DESCRIPTIONS OF MONITOR METHODS

Off-surge does not occur after solenoid 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)

- Not applicable
Sensor (The sensor below is determined to be normal)

- Not applicable

DTC SET CONDITIONS

Logic Flow Chart

Check Conditions

- Engine is being cranked.
- Battery positive voltage is between 10 and 16.5 volts.
Judgement Criteria

- The evaporative emission ventilation solenoid coil surge voltage (battery positive voltage + 2 volts) is not detected for 0.2 second.
- The ECM [M/T] or the PCM [A/T] monitors for this condition once during the drive cycle.
Check Conditions

- Battery positive voltage is at between 10 and 16.5 volts.
- ON duty cycle of the evaporative emission purge solenoid is 0 percent.
- Evaporative emission ventilation solenoid is ON.
- More than 1 second has elapsed after the above mentioned conditions have been met.
Judgement Criterion

- The evaporative emission ventilation solenoid coil surge voltage (battery positive voltage + 2 volts) is not detected for 1 second after the evaporative emission ventilation solenoid is turned OFF.

OBD-II DRIVE CYCLE PATTERN

Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 23 Monitors, Trips, Drive Cycles and Readiness Codes .

TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)

- Evaporative emission ventilation solenoid failed.
- Open or shorted evaporative emission ventilation solenoid circuit, harness damage, or connector damage.
- ECM failed.[ M/T]
- PCM failed.[ A/T]

DIAGNOSIS

Required Special Tools:

- MB991958: Scan tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991910: Main Harness A
- MB991923: Power Plant ECU Check Harness

STEP 1. Using scan tool MB991958, check actuator test item 15: Evaporative Emission Ventilation Solenoid.

CAUTION:
To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.

(1)Connect scan tool MB991958 to the data link connector.
(2)Turn the ignition switch to the "ON" position.
(3)Set scan tool MB991958 to the actuator test mode for item 15, Evaporative emission ventilation solenoid.

- An operation sound should be heard and vibration should be felt when the evaporative emission ventilation solenoid is operated.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the solenoid operating properly?

YES It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.

NO Go to Step 2.

STEP 2. Check harness connector F-13 at the evaporative emission ventilation solenoid for damage.

Q. Is the harness connector in good condition?

YES Go to Step 3.

NO Repair or replace it. Harness Connector Inspection.
Then go to Step 12.

STEP 3. Check the evaporative emission ventilation solenoid.

(1)Disconnect the evaporative emission ventilation solenoid connector F-13.

(2)Measure the resistance between evaporative emission ventilation solenoid side connector terminal No. 1 and No. 2.
Standard value: 17 - 21ohms [at 20°C (68°F)]

Q. Is the measured resistance between 17 and 21 ohms [at 20°C (68°F)]?

YES Go to Step 4.

NO Replace it. Then go to Step 12.

STEP 4. Measure the power supply voltage at evaporative emission ventilation solenoid harness side connector F-13.

(1)Disconnect the connector F-13 and measure at the harness side.
(2)Turn the ignition switch to the "ON" position.

(3)Measure the voltage between terminal No. 2 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 6.

NO Go to Step 5.

STEP 5. Check harness connector B-16X at MFI relay for damage.

Q. Is the harness connector in good condition?

YES Check connectors A-15 and C-26 at intermediate connectors for damage, and repair or replace as required. Harness Connector Inspection.
If intermediate connectors are in good condition, repair harness wire between MFI relay connector B-16X (terminal No. 4) and evaporative emission ventilation solenoid connector F-13 (terminal No. 2) because of open circuit or short circuit to ground. Then go to Step 12.

NO Repair or replace it. Harness Connector Inspection.
Then go to Step 12.

STEP 6. Measure the power supply voltage at ECM [M/T] or PCM [A/T] connector B-18 by using power plant ECU check harness special tool MB991923.

(1)Disconnect all ECM [M/T] connectors or PCM [A/T] connectors.
Connect the power plant ECU check harness special tool MB991923 between the separated connectors.
(2)Turn the ignition switch to the "ON" position.

(3)Measure the voltage between terminal No. 2 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 9.

NO Go to Step 7.

STEP 7. Check harness connector B-18 at ECM [M/T] or PCM [A/T] for damage.

Q. Is the harness connector in good condition?

YES Go to Step 8.

NO Repair or replace it. Harness Connector Inspection.
Then go to Step 12.

STEP 8. Check for open circuit and short circuit to ground between evaporative emission ventilation solenoid connector F-13 (terminal No. 1) and ECM [M/T] or PCM [A/T] connector B-18 (terminal No. 2).

Q. Is the harness connector in good condition?

YES Go to Step 10.

NO Repair or replace it. Harness Connector Inspection.
Then go to Step 12.

STEP 10. Check for harness damage between MFI relay connector B-16X (terminal No. 4) and evaporative emission ventilation solenoid connector F-13 (terminal No. 2).

NOTE:
Check harness after checking intermediate connectors A-15 and C-26. If intermediate connectors are damaged, repair or replace them. Harness Connector Inspection.
Then go to Step 12.

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 evaporative emission ventilation solenoid connector F-13 (terminal No. 1) and ECM [M/T] or PCM [A/T] connector B-18 (terminal No. 2).

NOTE:
Check harness after checking intermediate connector C-26. If intermediate connector is damaged, repair or replace it. Harness Connector Inspection. Then go to Step 12.

Q. Is the harness wire in good condition?

YES Replace the ECM or the PCM. When the ECM or the PCM is replaced, register the encrypted code. Immobilizer System.
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 23 Monitors, Trips, Drive Cycles and Readiness Codes.

(2)Check the diagnostic trouble code (DTC).

Q. Is DTC P0446 set?

YES Retry the troubleshooting.
NO The inspection is complete.