FAQ : How To Test Your Honda Main Relay

FAQ : How To Test Your Honda Main Relay

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The PGM-FI Honda main relay failure is a very common issue among Honda/Acuras and often times people may mis-diagnose the symptoms, or replace a different part. To test your PGM-FI main relay, you will have to first locate it in your vehicle. Many times it will be located near your driver side footwell in most Hondas and Acuras, near the fusebox for many Civics and Integras.

Other passenger vehicles like the Odyssey or CR-V will find the PGM-FI behind the passenger glovebox, mounted above the passenger side dashboard lower cover.

Once you have your PGM-FI removed, you will note the pinouts are labeled for your convenience and testing procedures. The part number for this unit can range, but for the Honda Civic and Acura Integra, you will want the part number 39400-S10-003, Fuel Injection Relay. the Mitsuba part number for this unit is RZ-0132 or RZ-0159.

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The Main Relay pinouts are as follows for testing purposes:

  • Pin 1 – To ECM/PCM Connector Terminal A16
  • Pin 2 – To Starter Switch
  • Pin 3 – To Chassis Ground
  • Pin 4 – To Fuel Pump
  • Pin 5 – To IGN 1
  • Pin 6 – To ECM/PCM Connector A11 and A24 for Fuel Pump
  • Pin 7 – To Battery

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1. To test your Honda Main Relay, first connect Pin 2 terminal on your relay to the positive terminal on your battery and the negative to Pin 1 terminal. Now check for continuity between Pin 5 and Pin 4 of the PGM-FI relay. If your relay has zero continuity in this test, it will need a replacement, if there is continuity, go to the next step.

2. Connect your positive terminal to Pin 5 of your relay and the negative terminal to Pin 3 of your relay. Now check continuity between Pin 7 and Pin 6. If your relay has zero continuity in this test, it will need a replacement, if there is continuity, go to the next step.

3. Connect your positive terminal to Pin 6 of your relay and the negative terminal to Pin 1 of your relay. You will be checking continuity between Pin 5 and Pin 4 in this last step. If there is continuity after these 3 steps, your problems with your car lie elsewhere and your main relay is good.

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You have now tested your Honda EFI Main relay, congratulations!

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