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.
1989 Geo Spectrum L4-91.5 1.5LFACTORY OEM SERVICE PROCEDURE
Electronic/Powertrain Control Module (ECM/PCM)
ECM Wiring Diagram (1 of 2):
10 = EFE HEATER
18 = ALTITUDE SWITCH
14 = FUEL CUT-OFF RELAY GROUND
21 = M/C SOLENOID GROUND
4 = ECM CEL GROUND
15 = ECM SHIFT LAMP AND THROTTLE OPENER OUTPUT
17 = COOLANT TEMPERATURE SENSOR INPUT
22 = ECM SENSOR GROUND
13 = AIR VSV SOLENOID ECM INPUT
ECM Wiring Diagram (2 of 2):
7 = 5V REFERENCE
5 = TPS SIGNAL
22 = SENSOR GROUND
8 = IDLE SWITCH INPUT
17 = COOLANT SENSOR INPUT SIGNAL
3 = OXYGEN SENSOR INPUT SIGNAL
20 = OXYGEN SENSOR CIRCUIT GROUND
1 = SYSTEM GROUND
2 = SYSTEM GROUND
19 = DISTRIBUTOR REFERENCE INPUT SIGNAL
9 = INLET AIR TEMPERATURE INPUT SIGNAL
Factory Service Tools
Use the Manual With the Right Hardware
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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.