1993 Honda Prelude VTECFACTORY OEM SERVICE PROCEDURE

Main Relay Harness

  1. Turn ignition off. Unplug main relay harness connector. Check for continuity between connector terminal No. 2 and chassis ground. See Fig 1 . If continuity exists, go to next step. If continuity does not exist, repair open in Black wire from terminal No. 2 to ground. See WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.
  2. Measure voltage between connector terminal No. 1 and body ground. If battery voltage exists, go to next step. If battery voltage does not exist, check wiring between battery and main relay and check ECM fuse in underhood relay box. Repair as necessary.
  3. Turn ignition on. Measure voltage between relay connector terminal No. 5 and body ground. If battery voltage exists, go to next step. If battery voltage does not exist, check wiring from ignition switch and main relay. Check fuse No. 23 on Prelude, No. 2 on Accord, or AGC on Civic and Civic Del Sol. Check wiring from fuse box to main relay. Repair or replace as necessary.
  4. Connect voltmeter to connector terminal No. 6 and body ground. Turn ignition switch to START position. If battery voltage exists, go to next step. If battery voltage does not exist, check wiring between ignition switch and main relay. Check fuse No. 9. Check wiring from fuse box to main relay. Repair or replace fuse or wiring as necessary.
  5. Connect jumper between connector terminals No. 5 and 7. Turn ignition on. Fuel pump should operate. If fuel pump fails to operate, check fuel pump wiring.
    Fig 1: Main Relay Harness Connector Term. ID (Accord Shown; Other Models Are Similar)
    G90I17150Courtesy of AMERICAN HONDA MOTOR CO., INC.
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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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