Enabling Conditions To Run EVAP Leak Detection Test
The following values are approximate and vehicle specific. Use the values seen in pretest/monitor test screen on the DRB III or suitable scan tool. See TSB 25-02-98 for more detail.
Cold start: with ambient temperature (obtained from modeling the inlet air temperature sensor on passenger vehicles and the battery temperature sensor on Jeep & truck vehicles) between 4C(40F) and 32C (90F) for 0.040 leak. Between 4C(40F) and 29C (85F) for 0.020 leak.
Engine coolant temperature within: -12to -8C (10to 18F) of battery/ambient.
Battery voltage between 10 and 15 volts.
If battery voltage drops below 10 volts for more than 5 seconds during engine cranking, the EVAP leak detection test will not run.
Low fuel warning light off (fuel level must be between 15% and 85% for 0.040 leak and 30% and 85% for 0.020 leak).
MAP sensor reading 22 in Hg or above (This is the manifold absolute pressure, not vacuum).
No Engine Stall During Test
If the system does not pass the EVAP Leak Detection Test, the following DTCs may be set:
P0442 - EVAP LEAK MONITOR 0.040 LEAK DETECTED
P0455 - EVAP LEAK MONITOR LARGE LEAK DETECTED
P0456 - EVAP LEAK MONITOR 0.020 LEAK DETECTED
P1486 - EVAP LEAK MON PINCHED HOSE FOUND
P1494 - LEAK DETECTION PUMP SW OR MECH FAULT
P1495 - LEAK DETECTION PUMP SOLENOID CIRCUIT
A DTC will not be set if a one-trip fault is set or if MIL is illuminated for any of the following:
Purge Solenoid Electrical Fault
All Engine Controller Self Test Faults
All Cam and/or Crank Sensor Fault
All Map Sensor Faults
Ambient/battery Temperature Sensor Electrical Faults
All Coolant Sensor Faults
All TPS Faults
LDP Pressure Switch Fault
EGR Solenoid Fault
All Injector Faults
BARO Out Of Range
Vehicle Speed Faults
LDP Solenoid Circuit
When the ignition key is turned to ON the LDP diaphragm should be in the down position and the LDP reed switch should be closed. If the EVAP system has residual pressure, the LDP diaphragm may be up. This could result in the LDP reed switch being open when the key is turned to ON and a P1494 fault could be set because the PCM is expecting the reed switch to be closed.
After the key is turned ON, the PCM immediately tests the LDP solenoid circuit for electrical faults. If a fault is detected, DTC P1495 will set, the MIL will illuminate, and the remaining EVAP Leak Detection Test is canceled.
If battery temperature is not within range, or if the engine coolant temperature is not within a specified range of the battery temperature, the PCM will not run tests for DTC P1494, P1486, P0442, P0455 and P0441. These temperature calibrations may be different between models.