Fixed Spark Mode Procedure

1. Purpose of test is to verify proper adjustment of spark timing. In this test procedure, the ECM commands a fixed spark advance of 10° and prevents EGR operation under the following conditions: Engine running and warm (parameter "P.0.4" above 185°F/85°C), engine speed below 900 RPM and transmission in "P".
2. Exit diagnostics (press "Auto") and jumper pins "A" and "B" (circuit Nos. 150 and 451) of ALDL connector. See Fig 1 . The SERVICE SOON" light may begin to flicker when pins are jumpered.

Fig 1: Location of ALDL Pins "A" and "B"