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.
1989 Geo Prizm LSi, AutomaticFACTORY OEM SERVICE PROCEDURE
Tests W/Codes
- Introduction
- Check Engine Light
- Retrieving Codes
- Trouble Code Identification Charts
- Clearing Codes
- Diagnostic Charts
- Diagnostic Circuit Check
- Chart A-1, No "Check Engine" Light
- Chart A-2, "Check Engine" Light Won't Flash "On" Steady
- Chart A-3, Engine Cranks But Will Not Run
- Chart A-5, Engine Cranks But Will Not Run, (Fuel System Electrical Test)
- Chart A-7, Fuel System Pressure Test
- Chart A-9, Cold Start Injector Valve
- Codes 12 & 13, No Rpm Signal No Signal For 2 Seconds
- Code 14, Ignition Signal Circuit No Signal
- Code 21, Oxygen Sensor Circuit Open Or Shorted Circuit
- Code 22, Coolant Temperature Sensor Circuit Open
- Code 24, Manifold Air Temperature (Mat) Sensor Circuit Low Temperature Indicated
- Code 25, Oxygen Sensor Circuit Lean Exhaust Indicated
- Code 26, Oxygen Sensor Circuit Rich Exhaust Indicated
- Code 31, Manifold Absolute Pressure Sensor Open Or Shorted Circuit
- Code 41, Throttle Switch Circuit
- Code 42, Vehicle Speed Sensor (VSS) Circuit
- Code 43, No Crank Signal No Signal From Starter
- Code 51, No A/C Signal
- Code 71, EGR Gas Temperature Sensor Circuit (CALIFORNIA Only)
- Summary
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.