P0442

DTC P0442 EVAPORATIVE EMISSION CONTROL SYSTEM LEAK DETECTED (SMALL LEAK)

CIRCUIT DESCRIPTION

DTC Detection Condition:

The vapor pressure sensor and the Canister Closed Valve (CCV) are used to detect abnormalities in the Evaporative Emission (EVAP) control system. The ECM evaluates if there is an abnormality in the evaporative emission control system based on the vapor pressure sensor signal.

DTCs P0442 or P0456 are recorded by the ECM when an EVAP leak from the components within the dotted line in Fig. 1 above, or when the vapor pressure sensor malfunctions.

HINT: Typical DTC output of each trouble part.

MONITOR DESCRIPTION

Monitor Strategy:

Typical Enabling Conditions:

Typical Malfunction Thresholds:

Monitor Result (Mode 06 Data):

The evaporative emission system consists of the vapor pressure sensor, the CCV (Canister Close Valve), the pressure switching valve and the EVAP VSV (Purge VSV). There systems are used by the ECM to detect malfunctions.

If the ECM detects stable vapor pressure in the fuel tank, the ECM will run a diagnostic test (step (a) to (e) below) once per drive cycle. The ECM will not run the test if the vapor pressure in the fuel tank is unstable. Driving on rough or winding roads causes movement of the fuel in the fuel tank and leads to unstable vapor pressure in the fuel tank.

The ECM performs the following steps:
a. The CCV is closed, sealing the system.
b. The fuel tank pressure stability is checked. The diagnostic test is disabled if the pressure change is more than the specified value.
c. The EVAP VSV is opened. This introduces negative pressure from the intake manifold to the fuel tank.
d. The EVAP VSV is closed and the negative pressure is sealed in the fuel tank.
e. The ECM monitors the increase in fuel tank pressure for:
1. A rapid increase in the internal pressure occurs. A small, 0.04 inch leak is present.
2. A slight increase in the internal pressure occurs. A very small, 0.02 inch leak is present.

If the ECM detects either of above conditions, it will interpret this as a leak in the EVAP system. The ECM will illuminate the MIL (2 trip detection logic) and set a DTC.

Wiring Diagram:

CONFIRMATION READINESS TEST

First Trip Procedure
a. The vehicle must be cold, and the ambient temperature must be between approximately 10 to 35°C (50 to 95°F).
b. The Intake Air Temperature (IAT) and the Engine Coolant Temperature (ECT) sensor almost the same value.

c. Clear the DTCs.
- Disconnect the battery terminals or the EFI1 fuse.
- Readiness tests will show INCMPL (incomplete).

d. Drive the vehicle according to the LA#4 driving cycle. Note the state of the Readiness Tests. They will change to COMPL (complete) as the evaluation monitors operate and if the system passes. This procedure may take approximately 20 minutes or more.

NOTE: Do not shut off the engine - the results will be invalid.

Pass Condition - No Problem Found by the ECM

If the EVAP evaluation monitor (EVAP EVAL), shows COMPL, go to the Non-Continuous Tests screen.

NOTE: Do not shut off the engine - the results will be invalid.

- Enter the following menus: ADVANCED OBD II / ONBOARD TESTS / NON-CONTINUOUS TESTS.
- If all of the tests in the "Time $02" category tests show "Pass", the evaluation monitor has operated and no problem was detected.

Fail Condition - Problem Detected by the ECM

If the EVAP evaluation monitor (EVAP EVAL) shows INCMPL, go to the Non-Continuous Test screen.

1. If all Tests show "Pass", the following may have occurred.
- The EVAP evaluation monitor did not operate.
- The EVAP evaluation monitor did not finish.
- The ECM withheld judgement.

2. If one or more of the tests in the time $02 category show "Fail", the EVAP evaluation monitor did operate and the ECM detected a problem.

3. Go to Continuous Tests screen. This is the only place DTC's are listed for the first trip.

NOTE: The DTC listed may not be valid. A second trip is needed to confirm the DTC.

Second Trip Procedure

a. Vehicle must be cold, ambient temperature between approximately 10 to 35°C (50 to 95°F).
b. Go to Readiness Tests screen.
c. Drive the vehicle according to LA#4 drive cycle. Note the state of the EVAP evaluation monitor (EVAP EVAL). This procedure may take approximately 20 minutes or more.

NOTE: Do not shut off the engine - the results will be invalid.

d. If Readiness Tests change to COMPL, the EVAP evaluation monitor has operated. Check for any stored DTC's.
- If a DTC has stored, the problem has been detected and confirmed by the ECM.
- If no DTC was found, EVAP evaluation monitor operated but no problem was detected.

INSPECTION PROCEDURE

HINT:
- Ask the customer if, after the MIL turned ON, the customer noticed that the fuel tank cap was loose and tightened it. Also ask the customer if the fuel tank cap was loose when refuelling. If the fuel tank cap was loose, the loose fuel cap caused the DTCs. If the fuel tank cap was not loose or if the customer was not sure if it was loose, troubleshoot according to the following procedure.
- Read freeze frame data using the hand-held tester or the OBD II scan tool. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.
- When ENGINE RUN TIME in the freeze frame data is less than 200 seconds, carefully check the vapor pressure sensor.