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.
1990 Geo Tracker LSi, AutomaticFACTORY OEM SERVICE PROCEDURE
Retrieving Codes
- Insert spare fuse into diagnostic switch terminal, located in fuse block under left side of dash. Turn ignition switch to ON position. Read trouble code(s). Proceed to CODE CHARTS for diagnosing stored codes.
- If no trouble codes are stored, CHECK ENGINE light will flash rapidly on then off until fuse is removed. Count the number of flashes and look for pauses in flashing to ensure no trouble codes are overlooked. If trouble codes are stored, code will flash 3 times and the lowest code will be given first.
TROUBLE CODE IDENTIFICATION CHART
| Code | Circuit Affected | Probable Cause | ||||||
|---|---|---|---|---|---|---|---|---|
| 13 | Oxygen Sensor | Open Circuit | ||||||
| 14 | Coolant Temp. Sensor | High Temp. Indicated | ||||||
| 15 | Coolant Temp. Sensor | Low Temp. Indicated | ||||||
| 21 (1) | Throttle Switch | Both Idle Switch & | ||||||
| Throttle Switch ON | ||||||||
| 21 (2) | Throttle Position Sensor | Signal Voltage High | ||||||
| 22 (2) | Throttle Position Sensor | Signal Voltage Low | ||||||
| 23 | Manifold Air Temp. Sensor | Low Temp. Indicated | ||||||
| 24 | Vehicle Speed | Incorrect Signal Voltage | ||||||
| 25 | Manifold Air Temp. Sensor | High Temp. Indicated | ||||||
| 31 | MAP Sensor | Signal Voltage Low High Vacuum | ||||||
| 32 | MAP Sensor | Signal Voltage High Low Vacuum | ||||||
| 41 | Ignition Signal | No Signal | ||||||
| 42 | Crank Angle Sensor | No Signal | ||||||
| 51 (3) | EGR System | Shorted Circuit | ||||||
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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.