1995 Geo Prizm Base, AutomaticFACTORY OEM SERVICE PROCEDURE

DTC Definitions

NOTE: DTCs will be recorded at various operating times. Some DTCs require sensor or switch operation for 5 seconds and others may require longer under certain conditions. Some DTCs may not set in a service bay operational mode.
DTC IDENTIFICATION

DTC Circuit Affected Probable Cause
12 No RPM Signal No Signal
13 No RPM Signal No Signal
14 Ignition Signal No Signal
16 PCM Control Signal PCM Failure
21 O2S Open/Short Circuit
22 ECT Sensor Open/Short Circuit
24 IAT Sensor Open/Short Circuit
25 O2S Air/Fuel Ratio Lean
26 Oxygen Sensor Air/Fuel Ration Rich
27 (1) Sub-O2S Open/Short Circuit
27 Sub-HO2S Open/Short Circuit
31 MAP Sensor Open/Short Circuit
41 TP Sensor Open/Short Circuit
42 VSS Open/Short Circuit
43 Crank Signal No Signal
51 Switch Condition Signal No Signal
52 Knock Sensor Open/Short Circuit
71 (1) EGR System Out Of Calibration
(1) 1.6L (VIN 6) California models only.
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.