Est Performance Check
- The ECM will set timing at a specified value when diagnostic test terminal of the ALDL connector is grounded. To check the EST operation, perform the following steps:
- Start and run engine at 1500 RPM with the ALDL diagnostic test terminal NOT grounded. Ground test terminal. When ALDL test terminal is grounded there should be a noticeable change in engine RPM. When a fault in the EST system takes place, a code 42 should be set.
- If code 42 is set, use appropriate chart for diagnosis. If symptom is engine miss and the direct ignition system is suspect, use CHART C-4D DIS MISFIRE in the 2.8L VINS [S,9] PFI CEC TESTS W/CODES article in the ENGINE PERFORMANCE section for proper diagnosis.