Diagnostic Aids

Engine Runs Okay, Check the following:

• Faulty light bulb.
• Circuit No. 419 open.
• Gauge fuse blown. This will result in no oil or generator light, seat belt reminder, etc.

Engine Cranks But Will Not Start, Check the following:

• Continuous battery fuse or fusible link.
• ECM ignition fuse open.
• Battery circuit No. 240 to ECM open.
• Ignition circuit No. 439 to ECM open.
• Poor connection at ECM.

Fig 1: No Service Engine Soon (SES) Light (Chart A-1, Schematic)

Courtesy of GENERAL MOTORS CORP.

Fig 2: No Service Engine Soon (SES) Light (Flow Chart A-1)

Courtesy of GENERAL MOTORS CORP.