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

Related videos
- Operation and testing of a Honda main relay (PGM-FI) - an SD Premium video
- How to identify a bad main relay on a Honda (PGM-FI)
- How to test fuel pressure, injector pulse and spark with basic tools

On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!

Disclaimer:
Due to factors beyond the control of ScannerDanner LLC, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. ScannerDanner LLC assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. ScannerDanner LLC recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of ScannerDanner LLC, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not ScannerDanner LLC.

[martythepainter]

I seldom comment on videos but wanted to say VERY WELL DONE! Bright video, loud and Clear audio, and no bullshit nobody has time for. Your the man.

[esroberto]

THANK YOU for the only USEFUL video on main relays on all of youtube. No one else bothered to show us exactly where the thing is mounted under the dash, they all assume we take cars apart for a living like they do -- useless! Can't thank you enough for this.

[kneedownGOD]

this was a reminder to look for the simple things first.just like today one of my techs couldnt get an a.c. compressor to run, after looking for almost an hour he came and got me, i checked schematic told him to check fuse 16 and he said he already checked all the fuses.i suggested a recheck and sure enough a blown fuse from the previous compressor, s bad clutch.loved this vid as always brother, GOD bless!

[doubledeeeeeeez]

Just fixed buddies 98 Honda Accord reflowing solder on bad board thanks to this video.  Kudos to uploader.  Wiggle check wires with key in 2 click position to verify you have cracked joints.  you will hear relay click and green key light will show.

[tommydeese]

Thanks Man, I thought I was going to have to change the the fuel pump until I saw your video, found circles on two of them soldered and fixed it but bought a new relay anyway.Great Video !!! Thanks

[thedronezone]

Hi, I've been searching for days to find the no-go-problem on my Honda Civic 2.0 i TD from 1998 with a ratteling main relay...
finally, after checking the complete wiring, I found this video. In a matter of minutes it is fixed !
Thank you thousand times,
Best regards,
Rudi (Belgium)

[RAFICKDAMISONMOYO]

I don't know Paul how to thank you for the information, Knowledge, Skills and Experience I'm gaining from you through your YouTube channel. You really Know things.

You Are Greater Person I'm my life as Auto Electrician.

Thanks Forever Paul Danner ❤❤❤❤❤

[patagualianmostly]

Spot on Video & advice there, ScannerDanner. Had an Accord fail to start right outside my door. Turned out the car was always parked in the shade at home but was outside in full sun that day for several refused to start.

Took out that board & there they were...little rings around those big terminals: Re-soldered them plus a couple that looked a bit up straight was a month more problems reported....despite the outside temps increasing on a daily basis. (Southern hemisphere.)

[ScannerDanner]

I totally just saw that! That confirms a loose fuse doesn't it. I will have to let this student know that he needs to tighten up the fuse terminals for sure. Great catch guys!

[happy]

I love that chirp that the 90's Hondas made when they start up. I used to own a 96 Prelude. It's still running after 300K miles.

[ScannerDanner]

no problem at all my friend. glad to help

[Avicron]

Thanks for taking time to put your great informative videos out . I was able to fix my main relay on my 91 civic and get running again . Cheers mate !

[iraysirs]

This is helpful information for my SE coupe 2002. Now I'm in the process of fixing that problem on my 1990 accord. Thank a million times.

[carpediem]

Thanks you so much again for the valuable information that I know most people would've charged me for, and also for your time. I'll have to do a good deed to compensate now. Cheers!

[mattsedlacek]

I had this problem on my 2003 Honda Pilot and it finally died completely on the freeway where I coasted to an exit safely. An hour of it cooling down and about 20 cranks and lots of taping the module with my knuckles didn't help start it. Had it towed home. Two days later, I tried starting it and it started right up. It had been doing this on and off for about nine months and just got worse and worse over time. What I learned was that my 25W soldering iron wasn't enough heat for the joint and the large relay pins, etc. I switched to a adjustable soldering station and at 700 degrees F it still wasn't enough heat. I finally cranked it up to 850 degrees F and it was able to do a good job. I first used solder wick to remove all the old solder and cleaned up the joint real well. I then used a rosin-core solder and got real nice new solder connections. The car started right up and has worked fine (so far) for about seven restarts, even when the engine was hot and then sat for about 10 minutes (a typical stop at a store, run-in, and back out). Really appreciate your videos. Thank you.

[technodance_me]

Thanks. This really helped out a bunch. I checked my fuse but didn't realize this relay was the issue. Popped it out soldered it and Bob's your uncle.

[COSHAM]

Thanks for that just fixed my sons 89 crx i never would have found the problem turned the key and it roared into life starts quicker now to. Thanks mate

[typhooni]

Thanks for the in depth look! Both my Accords have suffered from a bad relay.

[ScannerDanner]

It didn't blow, it was an arch from poor contact, at least that's what I think it was. I didn't even realize that happened until you guys pointed it out. The fuse never blew so it has to be from that. Also that matches why a simple bump with the foot could pop the fuse out. It was loose to begin with.

[mdvalenz]

Thank you for the walk through. My wife's car is starting again.