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 Isuzu Trooper II Base, AutomaticFACTORY OEM SERVICE PROCEDURE
TCU Code 1 - Knock Sensor Signal
- Check for short between ECU and TCU harness. Disconnect harness connectors at ECU and TCU. Check that continuity exists between pin No. 23 on ECU and pin No. 20 on TCU. Check that no continuity exists between pin No. 20 on TCU and ground. If tests are not proper, repair or replace harness.
- If tests in step 1) are proper, go to ECU CODE 66 (IMPULSE) - KNOCK SENSOR CIRCUIT .
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.