P0442

Engine Controls Schematics: MAF Sensor, EVAP System, EGR Valve:

SYSTEM DESCRIPTION
The EVAP SMALL LEAK TEST is based on applying vacuum to the EVAP system and monitoring vacuum decay. The PCM monitors vacuum level via the Fuel Tank Pressure sensor input. At an appropriate time, the EVAP canister purge valve and the EVAP vent valve are turned on allowing engine vacuum to draw a small vacuum on the entire evaporative emission system. After the desired vacuum level has been achieved, the EVAP purge valve is turned off, sealing the system. A leak is detected by monitoring for a decrease in vacuum level over a given time period, all other variables remaining constant. A small leak in the system will cause DTC P0442 to be set.

CONDITIONS FOR RUNNING THE DTC
^ No TP sensor, ODM, IAT sensor, or MAP sensor DTCs set.
^ The DTC P0440 diagnostic test has passed.
^ Startup engine coolant temperature is not more than 4°C and 30°C (40°F and 86°F).
^ Startup engine is not more than 8°C (14°F).
^ Startup Intake air temperature not more than 2°C and 30°C (40°F and 86°F).
^ Startup intake air temperature not more than 2°C (4°F).
^ Fuel tank level is between 15 percent and 85 percent.
^ BARO is more than 75 kPa.

CONDITIONS FOR SETTING THE DTC
A vacuum decay condition indicating a small leak is detected during the diagnostic test.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM will illuminate the MIL during the first trip in which the diagnostic runs and fails.
^ If equipped with traction control, the PCM will command the EBTCM via the serial data circuit to turn OFF traction control and illuminate the TRACTION OFF lamp.
^ The PCM will store conditions which were present when the DTC set as Freeze Frame/Failure Records data.

IMPORTANT: Although this diagnostic is considered type A, it acts like a type B diagnostic. Whenever the EVAP diagnostics report that a system has passed, or if the battery has been disconnected, the diagnostic must fail during 2 consecutive cold start trips before setting a DTC. The initial failure is not reported to the diagnostic executive or displayed on a scan tool. A passing system always reports to the diagnostic executive immediately.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The PCM will turn the MIL OFF during the third consecutive trip in which the diagnostic has been run and passed.
^ The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC can be cleared by using a scan tool.

DIAGNOSTIC AIDS
Inspect for the following:
^ Cracked or punctured EVAP canister.
^ Damaged source vacuum line, EVAP purge line, EVAP vent hose or fuel tank vapor line.
^ Poor connection at PCM.
Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
^ Damaged harness.
Inspect the wiring harness to the EVAP vent valve EVAP canister purge valve and the fuel tank pressure sensor for an intermittent open or short circuit.

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

TEST DESCRIPTION

Steps 1 - 4:

Steps 5 - 11:

Steps 12 - 16:

The numbers below refer to the step numbers on the diagnostic table:
1. The powertrain On-Board Diagnostic (OBD) System Check prompts you to complete some of the basic checks and store the Freeze Frame and Failure Records data on the scan tool if applicable.
2. If a vent valve or EVAP purge valve electrical malfunction is present, the purge system will not operate correctly. Repairing the electrical malfunction that caused the additional DTC to set will very likely correct the condition that set this DTC.
3. Inspects for a fuel tank pressure sensor stuck high condition. The fuel tank pressure must be relieved by removing the canister line from the fuel tank or EVAP canister. The fuel fill cap will not relieve the tank due to a check valve in the filler neck. the check valve seals when pressure is applied to prevent vapors from escaping through the filler neck. The scan tool should read within 1.0 inch H2O of the specified value.
4. Verifies that the fuel tank pressure sensor accurately reacts to EVAP system pressure changes. The EVAP station is pressurizing a sensor that normally reads vacuum. The scan tool reads high pressure at 0 volts and high vacuum at 5 volts. The scan tool can only read a max pressure of 6.0 inches of H2O (0 volts). However the EVAP service station can pressurize the system to much higher pressures. The scan tool value should be within 0.5 inch H2O of the specified value.
5. Inspects for a small leak in the EVAP system.
6. Inspects for a leak in the canister, vent line, or a leaking EVAP vent valve.
10. Inspects for a leaking or stuck open EVAP canister purge valve. The scan tool should read within 1.0 inch HG of the specified value.
16. The EVAP station is pressurizing a sensor that normally reads vacuum. The scan tool reads high pressure at 0 volts and high vacuum at 5 volts. The scan tool can only read a max pressure of 6.0 inches of H2O (0 volts), however the EVAP service station can pressurize the system to much higher pressures. The scan tool value should be within 0.5 inch H2O of the specified value.