1987 Honda Prelude Base, AutomaticFACTORY OEM SERVICE PROCEDURE

Code 7, Throttle Angle Sensor

  1. Turn off ignition. Remove clock fuse in the under-hood relay box for 10 seconds to reset ECU. Start engine and observe PGM-FI warning light. If light is off, problem is intermittent. Test drive and check again.
  2. If light is on, turn ignition off. Disconnect 3-wire connector at throttle position sensor. Turn ignition on. Measure voltage between Yellow/White (pos.) and Green/White (neg.) terminals. If voltage is not about 5 volts, go to step 5). If voltage is about 5 volts, turn ignition off. Reconnect sensor connector. Connect system checker harness between ECU and ECU connector.
  3. Turn ignition on. Measure voltage between terminals C7 (pos.) and C12 (neg.). Voltage should read .5 volt at closed throttle, and about 4.5 volts at wide open throttle, with a smooth transition between the lower and upper voltage specification as the throttle is depressed.
  4. If sensor does not respond as indicated in step 3), replace throttle sensor or repair open or short in Red/Yellow wire between ECU terminal C7 and throttle sensor. On Prelude models, also check for short in Red/Yellow wire between throttle angle sensor and automatic transmission control unit. If throttle sensor responds as indicated, substitute a known good ECU. If condition is rectified, replace original ECU.
  5. If voltage reading between Yellow/White (pos.) and Green/White (neg.) terminals in step 2) was not about 5 volts, measure voltage between ground and Yellow/White wire terminal. If voltage is now about 5 volts, repair open in Green/White wire between ECU terminal C12 and throttle sensor. If about 5 volts is not present between ground and Yellow/White wire, turn ignition off.
  6. Connect system checker harness between ECU and ECU connector. Turn ignition on. Measure voltage between terminals C13 (pos.) and C12 (neg.). If voltage is still not about 5 volts, go to next step. If voltage is about 5 volts, repair open Yellow/White wire between ECU terminal C13 and throttle sensor.
  7. Substitute a known good ECU. If condition is rectified, replace original 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.

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