1991 Acura Legend Base, AutomaticFACTORY OEM SERVICE PROCEDURE

Code 6: Coolant (TW) Sensor

NOTE: For wiring diagrams, see WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section. For vacuum diagrams, see VACUUM DIAGRAMS article in the ENGINE PERFORMANCE Section.
  1. Turn ignition off. Remove ACG fuse in underdash fuse box for 10 seconds to reset ECU. Start engine, and connect jumper wire to diagnostic connector. Observe CHECK ENGINE light. If light is not flashing, problem is intermittent. Check for poor or loose connections at TW sensor and at connector C353 at right shock tower. Test drive, and check again.
  2. If CHECK ENGINE light flashes Code 6, warm engine until cooling fan comes on. Turn ignition off. Disconnect 2-pin connector at TW sensor. Measure resistance between sensor terminals. If reading is 200-400 ohms, go to next step. If reading is not 200-400 ohms, replace sensor.
  3. Turn ignition on. Measure voltage between Red/White wire and ground. If about 5 volts are present, go to step 5). If 5 volts are not present, disconnect ECU connector "D" from ECU only. Connect ECU test harness to "D" connector of ECU side only. See Figure .
  4. Measure voltage between ECU terminals D13 (positive) and D22 (negative). If about 5 volts are present, repair open or short in Red/White wire between ECU and TW sensor. If voltage is not about 5 volts, substitute a known good ECU, and recheck. If 5 volts are now present, replace ECU.
  5. If 5 volts are present from test in step 3), measure voltage between Red/White (positive) and Green/White (negative). If about 5 volts are present, check for open circuit in Green/White wire between ECU terminal D22 and TW sensor. If 5 volts are not present, substitute a known good ECU. If condition goes away, replace ECU.
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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.