How to test and fix a PGM-FI main relay - Honda/Acura

Honda PGM-FI Main Relay Testing (1998 Honda Prelude)
How to test and fix a main relay on a Honda or Acura.

Engine Performance Diagnostics chapter 18

Symptoms (typical of a main relay issue)
- intermittent no start
- start/stall
- stalls and will not restart for a period of time

Fix
- replaced PGM-Fi main relay fuse

Tests shown
- how to determine what is powered by the main relay
- main relay wiring diagram review
- how to identify condition of the main relay by testing for power at the fuel injectors and idle speed control motor
- how to test a PGM-FI main relay
- how to locate the main relay
- how to remove the main relay
- how to locate a cracked solder joint on a circuit board

Tools used
- incandescent test light
- soldering gun

Playlist
- (Chapters 17, 18 and 19) Fuel Injector Testing
https://www.youtube.com/playlist?list=PLAFYVCyenqcoYm94zK0-EP0ICsGWj_ICs

Related videos
- Operation and testing of a Honda main relay (PGM-FI) - an SD Premium video
https://youtu.be/QVxOQTSPyGY
- How to identify a bad main relay on a Honda (PGM-FI)
https://youtu.be/6CMZ4g8n0FQ
- How to test fuel pressure, injector pulse and spark with basic tools
https://youtu.be/SUxagOAVS5M

For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available at www.scannerdanner.com as an eBook or paper book.
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