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.
1992 Geo Prizm Base, StandardFACTORY OEM SERVICE PROCEDURE
Trouble Code Definitions
FAULT CODE IDENTIFICATION
| Code | Circuit Affected | Probable Cause | ||||||
|---|---|---|---|---|---|---|---|---|
| 12 | No RPM Signal | No Signal For 2 Seconds | ||||||
| 13 | No RPM Signal | No Signal For 2 Seconds | ||||||
| 14 | Ignition Signal | No Signal | ||||||
| 21 | Oxygen Sensor | Open/Short Circuit | ||||||
| 22 | Coolant Temp. Sensor | Open/Short Circuit | ||||||
| 24 | Intake Air Temp. Sensor | Open/Short Circuit | ||||||
| 25 | Oxygen Sensor | Lean Exhaust Indicated | ||||||
| 26 | Oxygen Sensor | Rich Exhaust Indicated | ||||||
| 27 (1)(2) | Sub-O2 Sensor | Open/Short Circuit | ||||||
| 31 (2) | Mass Airflow Sensor | Short Circuit | ||||||
| 31 (3) | MAP Sensor | Open/Short Circuit | ||||||
| 41 (2) | Throttle Position Sensor | Open/Short Circuit | ||||||
| 41 (3) | Throttle Position Switch | Incorrect Signal Voltage | ||||||
| 42 | Vehicle Speed Sensor | Incorrect Signal Voltage | ||||||
| 43 | No Crank Signal | No Signal From Starter | ||||||
| 51 | Switch Condition Signal | No Signal Present | ||||||
| 52 (2) | Knock Sensor Signal | Open/Short Circuit | ||||||
| 53 (2) | Knock Control Signal | Faulty ECM | ||||||
| 71 (1) | EGR Temp. Sensor | Out Of Calibration | ||||||
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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.
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