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 Toyota 4Runner Base, AutomaticFACTORY OEM SERVICE PROCEDURE
Diagnosis & Testing: Diagnosis
- Ensure all engine systems NOT related to TCCS are fully operational. DO NOT proceed with testing until all other problems have been repaired. Ensure fuses, fusible links and wire connectors are in good condition before diagnosing ECU.
- Enter diagnostic mode and record trouble codes. Exit diagnostic mode. If no trouble codes were displayed, proceed to appropriate DIAGNOSTIC CIRCUIT CHECK charts. Follow instructions given there.
- If no trouble codes were displayed after performing diagnostic circuit check, perform voltage and resistance checks. See appropriate ECU PIN VOLTAGE TEST chart in this article.
- If trouble codes are displayed, perform tests to confirm cause of malfunction which set the corresponding trouble code.
- After any repairs are made, clear trouble codes and perform diagnostic circuit check. Normal system operation code should be displayed if repair solved cause of malfunction.
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.
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