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.
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HOMESERVICE MANUALSTOYOTA1990TERCEL BASE, 2D COUPE, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - TESTS W/CODES - EFI
1990 Toyota Tercel Base, 2D Coupe, Standard
Engine Controls - Tests W/Codes - EFI
1990 Toyota Tercel Base, 2D Coupe, StandardSECTION Engine Controls - Tests W/Codes - EFI
- Introduction
- Ecu Location
- "Hard Failures"
- "Intermittent Failures"
- Check Engine Light
- Retrieving Trouble Codes
- Notes On Trouble Codes
- Clearing Trouble Codes
- Repair Procedure
- Summary
- Trouble Code Charts
- Trouble Code Diagnostic Hints
- Diagnostic Circuit Check
- Ecu Terminal Identification
- Diagnostic Tests
- Test 1 - Ecu (B+) Circuit
- Test 2 - Ecu Power Source
- Test 3 Or Code 12, 13, 14 - Ignition & Rpm Signal
- Code 21 - Oxygen (O2) Sensor Signal
- Test 4 Or Code 22 - Coolant Temperature Sensor Signal
- Test 5 Or Code 24 - Intake Air Temperature
- Code 25 - Lean Air Fuel Mixture
- Code 26 - Rich Air Fuel Mixture
- Test 6 Or Code 31 - Vacuum Switch Signal
- Test 7 Or Code 41 - Throttle Position Switch Signal
- Code 42 - Vehicle Speed Sensor Signal
- Test 8 Or Code 43 - Starter Signal
- Test 9 Or Code 71 - EGR System Malfunction
- Test 10 - Injector Circuit
- Test 11 - "Check Engine" Light Circuit
- Test 12 - A/C Switch Circuit
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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.