1991 Geo Storm Base, 2D Hatchback, AutomaticFACTORY OEM SERVICE PROCEDURE

Retrieving Codes

  1. Ensure ignition switch is in the OFF position. Using a jumper wire, connect ground and diagnostic terminals of Assembly Line Diagnostic Link (ALDL) White connector. See Fig 1 . Connector is located behind right kick panel in passenger compartment. Turn ignition switch to ON position. Read fault code(s). Proceed to appropriate charts under DIAGNOSTIC CODE CHARTS to diagnose fault codes.
    WARNING: Ensure jumper wire is connected to ALDL White connector. A connector for Supplemental Inflatable Restraint (SIR) system is located next to ALDL connector.
  2. If no fault codes are stored, CHECK ENGINE light will flash on and off rapidly until jumper wire is disconnected. Count the number of flashes and look for pauses in flashing to ensure no fault codes are overlooked. If fault codes are stored, code will flash 3 times starting with the lowest code.
Fig 1: Identifying ALDL White Connector Terminals (Storm)
G121598Courtesy of GENERAL MOTORS CORP.
FAULT CODE IDENTIFICATION (STORM)

Code Circuit Affected Probable Cause
13 Oxygen Sensor Open Circuit
14 Coolant Temp. Sensor High Temp. Indicated
14 Coolant Temp. Sensor Low Temp. Indicated
21 Throttle Position Sensor Signal Voltage High
21 Throttle Position Sensor Signal Voltage Low
23 Intake Air Temp. Sensor Low Temp. Indicated
23 Intake Air Temp. Sensor High Temp. Indicated
24 Vehicle Speed Sensor Incorrect Signal Voltage
32 EGR System EGR Failure
33 MAP Sensor Signal Voltage High, Low Vacuum
33 MAP Sensor Signal Voltage Low, High Vacuum
42 Electronic Spark Timing Open/Short Circuit
44 Oxygen Sensor Lean Exhaust Indicated
45 Oxygen Sensor Rich Exhaust Indicated
51 ECM Failure ECM Failed Or PROM Failure
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  • • You smell fuel, burning insulation, or see smoke.
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  • • The engine overheats, stalls repeatedly, or misfires under load.
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