EVAP Leak Detection Test Tips
EVAP Leak Detection Test TipsIf all of the conditions for running the EVAP Leak Detection Test (see "Enabling Conditions to Run EVAP Leak Detection Test" section on page 5 of this bulletin) are not met, the tests will not run and could lead to misdiagnosis.
- If the "battery temperature" value displayed on the MUT-II is too high, you can blow cool air on the PCM with a fan to cool the PCM sensor that estimates battery temperature. If "battery temperature" is too low, try warming the PCM by blowing warm air on it. However, do not expose the PCM to extreme temperatures or the PCM could be damaged.
- QUICK SYSTEM CHECK
If you want to quickly determine if a fault condition is still present, you can perform a quick check of the EVAP system as follows. The readiness test will not complete, because purge will not take place, but you will be able to see if the PCM detects any problems that could set DTC 183, 184, 187, 160, or 161.
Connect a test light, logic probe, or voltmeter between the LDP solenoid control terminal (A-109, terminal 3) and B+ by backprobing into the connector with the harness connected to the LDP. When the PCM energizes the LDP solenoid, you will hear a click from the LDP and your tester will indicate that the solenoid is turned on. (You can also touch the LDP and feel the solenoid clicking.)
Refer to the EVAP Leak Detection Test Sequence chart and description on pages 6 - 8 of this bulletin. Compare the LDP solenoid activity with the monitor sequence in the chart. By watching to see which tests complete, you can see if any conditions are present that the PCM considers abnormal. If LDP solenoid activity indicates the possibility of a system leak, allow LDP solenoid activity to complete (which may take several minutes), then turn off and restart the engine. Allow the leak detection sequence to run, which may take several minutes. If a leak of 1.0 mm (0.040") or more is judged to be present, the PCM should turn on the MIL and set a DTC.
^ When performing the above quick check procedure, if the engine coolant temperature (ECT) reading on the MUT-II is not within 10°F of "battery temperature" reading, it may be necessary for the vehicle to sit several hours to cool sufficiently. Or you can save time by substituting an inexpensive resistor for the ECT sensor to bring the reading into the required range. This will also allow you to run the test repeatedly (if necessary) since the resistor provides a consistent ECT reading within the required temperature range.
Insert a resistor as follows to change the coolant temperature reading to meet required monitor conditions:
a. Note the battery temperature reading on the MUT-II.
b. Turn the ignition key to OFF.
c. Disconnect the harness connector from the coolant temperature sensor.
d. The chart below lists three resistor values that will cover the temperature range for the EVAP leak detection test to run. Select a resistor value that will bring the ECT reading to within 10°F of the battery temperature reading.
! WARNING
To prevent damaging the connector, use only a 1/2 watt resistor (Radio Shack or equivalent) which has the correct lead diameter to properly fit into the connector terminals.
e. Bend the resistor leads so they are parallel and spaced the same distance apart as the coolant temperature sensor terminal pins.
f. Insert the resistor leads into the ECT harness connector in place of the ECT.
g. Turn the A/C on at maximum setting so that the cooling fan will come on when the engine is running. If the vehicle is not equipped with A/C, use a jumper wire between the cooling fan and B+ to activate the fan.
h. Turn the ignition key to ON and confirm that the engine coolant temperature (ECT) reading on the MUT-II is within 100 F of "battery temperature" reading.
i. Clear any DTCs from PCM memory that may have set. Start the engine and compare LDP solenoid operation with the "Leak Detection Sequence" chart.