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.
1991 Geo Metro XFiFACTORY OEM SERVICE PROCEDURE
Retrieving Codes
- Perform diagnostic circuit check before diagnosing vehicle using self-diagnostic system. See appropriate DIAGNOSTIC CIRCUIT CHECK chart under DIAGNOSTIC CODE CHARTS.
- Fault code(s) can be retrieved through either of the 2 diagnostic switch terminals. See Fig 1. One is located in the diagnostic connector in engine compartment, and the other one is located in the fuse block in the passenger compartment.
- To retrieve code(s) using the diagnostic terminal in fuse block, insert spare fuse into diagnostic switch terminal. The ECM will toggle the CHECK ENGINE light, flashing code(s).
- To retrieve code(s) using the diagnostic connector in the engine compartment, ground terminal "B" (diagnostic switch terminal) of connector. The ECM will then output self-diagnostic code(s). Both diagnostic switch terminals, when grounded, will set ignition timing to base timing (XFi w/ESC).
- If no fault codes exist, ECM will flash Code 12. If fault codes are stored, the lowest code will be flashed first. Each code will be displayed 3 times. Proceed to appropriate chart(s) under DIAGNOSTIC CODE CHARTS to diagnose fault codes.
FAULT CODE IDENTIFICATION
| Code | Circuit Affected | Probable Cause | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 12 | System Is Normal | ... | ||||||||
| Oxygen Sensor | Open Circuit | 13 | ||||||||
| Coolant Temp. Sensor | High Temp. Indicated | 14 | ||||||||
| Coolant Temp. Sensor | Low Temp. Indicated | 15 | ||||||||
| Throttle Switch | Idle Switch & Throttle Switch Are On | 21 (1) | ||||||||
| Throttle Position Sensor | Signal Voltage High | 21 (2) | ||||||||
| Throttle Position Sensor | Signal Voltage Low | 22 (2) | ||||||||
| Manifold Air Temp. Sensor | Low Temp. Indicated | 23 | ||||||||
| Vehicle Speed Sensor | No Speedometer | 24 | ||||||||
| Manifold Air Temperature | High Temp. Indicated | 25 | ||||||||
| MAP Sensor | Signal Voltage Low, High Vacuum | 31 | ||||||||
| MAP Sensor | Signal Voltage High, Low Vacuum | 32 | ||||||||
| Ignition Signal | No Signal | 41 | ||||||||
| Crank Angle Sensor | No Signal For 2 Seconds | 42 (3) | ||||||||
| EGR System | EGR VSV Inoperative | 51 (4) | ||||||||
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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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