1987 Honda Prelude Base, AutomaticFACTORY OEM SERVICE PROCEDURE

Code 15, Ignition Output Signal

  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 6-wire connector at ignitor. Turn ignition on. Measure voltage between ground and Black/Yellow wire terminal on ignition side of harness. If battery voltage is not present, repair open Black/Yellow wire between connector and ignition switch.
  3. If battery voltage is present, turn ignition off. Reconnect 2-wire or 6-wire connector. Connect system checker harness between ECU and ECU connector. Turn ignition on. Individually, measure voltage between terminal A18 (neg.) and terminals B15 and B17. If battery voltage is present, go to step 4). If battery voltage is not present, go to step 5).
  4. Substitute a known good ECU. If condition is rectified, replace original ECU.
  5. Turn ignition off. Disconnect 6-wire ignitor connector and connectors from ECU only, not main harness. Check for continuity between White wires and ECU terminals B15 and B17 and ignitor. If continuity does not exist, repair as necessary. If continuity does exist, check for continuity between ground and White wires of 6-wire connector. If continuity exists, repair short to ground. If continuity does not exist, replace ignitor.
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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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