Evaporative Systems Monitoring

Evaporative Systems Monitoring (LDP System)

Overview of Evaporative System Leak Monitoring Conditions:

Comparing the temperature signals and correcting for the lowest possible temperature value provides safeguards against setting faults and ultimately an erroneous MIL activation. The following scenarios provide insight into how the system can provide guaranteed test results.
- The CAN bus ambient temperature signal is within range and a leak is detected during the leak test. After the conditions are met for comparing the CAN bus signal with the intake air temperature sensor signal which is detected as;
1. Out of range: test is ended with no fault stored
2. Within range, fault stored
- The ambient temperature is out of range at the time of engine start, this leads to a temporary end of test, the leak test is carried out as soon as all conditions are OK for an accurate test result
- Only when the ambient temperature is within specified range and no leak is detected during the leak test is the system considered to be "leak free".

ECM logic paths for meeting leak detection pre test conditions:

The following flow charts show how the ECM scrutinizes all operating conditions to minimize possible false test results. The Yes/No paths through the flow charts provide four possibilities based on conditions for the system to either abort or run the Leak Detection Test as follows:

Flow Chart 1: Cold Start Conditions

Yes Path = Continuation into next requirement and ultimately run the LDP while in Cold Start Conditions.

No Path = Go to next flow chart as required:

1. Temporary end of test. Condition causes the ECM to proceed to the "Test Repetition Flow Chart" (checked every 100 ms) for repeated attempts.
2. Final end of test. Final end of test informs ECM to proceed to the "Final End Of Test Flow Chart" to determine if the test can continue or abort until next drive cycle. (checked every 100 ms).

Flow Chart 1: Cold Start Conditions








Flow Chart 2: Temporary End of Test








Flow Chart 3 : Test Repetition Flow Chart







Flow Chart 4: Final End of Test Flow Chart