Est Performance Check

The ECM will set timing at a specified value when ALDL "test" terminal is grounded. To check the EST operation, perform the following steps:

1. Start and run engine at 1500 RPM. Ground ALDL "test" terminal. When "test" terminal is grounded there should be a noticeable change in engine RPM. When a fault in the EST system occurs, a Code 42 should be set.
2. If a Code 42 (or 43) is set, use appropriate CODE chart below for diagnosis. If symptom is engine miss and the DIS is suspected, use CHART C4M - DIS MISFIRE DIAGNOSIS below for diagnosis.