GM Import / GEO >> 91 Geo 1.6L

91 Geo 1.6L

Accessing Trouble Codes

To get a trouble code out of the ECM, it is necessary to jumper the BLACK wire and the BLUE/YELLOW wire at the ECM check connector, located under the hood by the battery.

Clearing Trouble Codes

  1. Clearing Stored Codes. (Long Term Memory)
    1. Turn “OFF” the ignition.
    2. Remove the tail/dome fuse for 20 seconds.
    3. Re-install fuse.
  1. Resetting the “CHECK ENGINE” light. ONLY after the maintenance service has been performed (Federal Only).
    1. Locate the cancel switch behind the access panel, below the steering column.
    2. To reset the switch, move the switch to “OFF.”

NOTE: Federal equipped vehicles have a cancel switch which needs to be reset after the 50,000, 80,000, and 100,000 mile maintenance service is completed.

Trouble Codes

89 – 92 GEO

13 Oxygen Sensor circuit.
14 Coolant Temperature Sensor circuit. High temperature indicated.
15 Coolant Temperature Sensor circuit. Low temperature indicated.
21 Throttle Position Sensor Signal Voltage High (Automatic Transmission).
22 Throttle Position Sensor Signal Voltage Low.
23 Intake Air temperature (MAT) Sensor. Low temperature indicated.
24 Vehicle Speed Sensor circuit.
25 Intake Air temperature (MAT) Sensor. High temperature indicated.
31 MAP Sensor circuit – Signal Voltage Low Vacuum.
32 MAP Sensor circuit – Signal Voltage High Vacuum.
33 MAP Sensor circuit.
41 Ignition Signal circuit.
42 Crank Angle Sensor.
44 Idle switch open or improper adjustment.
45 Idle Switch Circuit Grounded or Improper Adjustment.
46 Idle Speed Control Motor circuit.
51 EGR circuit.
53 Ground circuit.


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