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.
1988 Chevrolet Spectrum ExpressFACTORY OEM SERVICE PROCEDURE
Feedback Carburetor System
- Description
- Operation
- Trouble Shooting
- Notes
- Feedback Carburetor System
- Diagnostic Circuit Check
- Clearing Trouble Code Memory
- System Performance Check
- Test 1 - Dwell Fixed Less Than 15 Degrees
- Test 2 - Dwell Fixed Between 15-50 Degrees
- Test 3 - Dwell Fixed Greater Than 50 Degrees
- Test 4 - TPS Wide Open Throttle
- Test 5 - "Check Engine" Light Inoperative
- Test 6 - Will Not Flash Code 12
- Test 7 - Fuel-Cut System Operational Check
- Trouble Codes
- CODE 12 (No Distributor Reference Pulse to ECM)
- CODE 13 (Open O2 Sensor Circuit)
- CODE 14 (Shorted Coolant Sensor Circuit)
- CODE 15 (Open Coolant Sensor Circuit)
- CODE 21 (TPS & Idle Switch Circuit)
- CODE 22 (Fuel-Cut Relay Circuit Open or Grounded)
- CODE 23 (Feedback Solenoid Circuit)
- CODE 25 (Vacuum Switching Valve Circuit)
- CODE 42 (Constant High Voltage from Fuel-Cut Relay)
- CODE 44 (Lean Exhaust Indication)
- CODE 45 (Rich Exhaust Indication)
- CODE 51 (PROM Problem)
- CODE 53 (Constant High Voltage Reading from Vacuum Switching Valve)
- CODE 54 (Constant High Voltage Reading from Feedback Solenoid)
- CODE 55 (Faulty O2 Sensor or ECM)
- Component Testing
- Wiring Diagrams
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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