Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1991 Geo Tracker Base, RWDFACTORY OEM SERVICE PROCEDURE
Diagnostic Circuit Check
NOTE:
Test numbers refer to test numbers on diagnostic chart.
Diagnostic circuit check is the starting point for identifying a problem caused by the fuel injection system.
- If CHECK ENGINE light illuminates with ignition on and engine off, it confirms battery and ignition voltage to ECM.
- ECM uses the CHECK ENGINE light to flash 2-digit codes. All fault codes stored in ECM will be flashed 3 times. The lowest code number will be flashed first. If no fault codes are stored, Code 12 will flash (until fuse is removed from fuse box), indicating ECM diagnostics are working. If engine starts, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section. If engine cranks but will not start, see BASIC TESTING article in the ENGINE PERFORMANCE Section.
- Record all fault codes. Go to appropriate code chart(s).
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.