1993 Geo Prizm Base, StandardFACTORY OEM SERVICE PROCEDURE

Malfunction Indicator Light (Mil): Notes

NOTE: MIL is also known as the CHECK ENGINE light.

All vehicles are equipped with a Malfunction Indicator Light (MIL), located on instrument panel. Light comes on, as a bulb check, when ignition switch is turned to ON position and engine is not running. Light should not flash at this time and should go out when engine is started.

If MIL remains on or flashes with engine running, self-diagnostic system has detected a problem. If problem goes away, light will go out after 10 seconds, but a fault code will be stored in ECM memory.

All trouble codes except Code 16 (PCM control signal on Prizm LSi), Code 43 (crank signal) and Code 51 (switch condition signal) are stored in ECM memory. Codes 16, 43 and 51 are erased from memory as soon as ignition is turned off. In order to detect an active Code 16, 43 or 51, ignition switch must be in ON position (engine off) with diagnostic request terminal TE1 in Data Link Connector (DLC) grounded. See Figure . Diagnostic check connector is located on left shock tower.

If ignition switch is turned to OFF position at any time during this procedure, a hard or active Code 16, 43 or 51 will be lost.

Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.