96 accord no start without scan tool

Alright guys got a new one here I've never seen. 96 honda accord 2.2 liter. Car came to me half torn apart for a head gasket job. Put it back together and car wouldnt start. Traced it back to no power to the fuel pump. Fuse had power, found the pgmf1 relay which incorporates the fuel pump relay. Removed it from car and tested it, tested fine. Decided to plug my scanner in, car fired right up. I thought nothing of it and chalked it up to the relay being removed might have jarred it fixed. Let the car run and topped off coolant, before I cut the car off I removed my scanner and the car died immediately. Wouldnt start back until I plugged scanner in. Anyone ever ran across this? I'm guessing my scanner is acting as a connection for whatever the fuel pump relay is missing. Wiring diagram shows 2 grounds for the DLC connector. One of which shares a ground with the pgmf1 (fuel pump relay). Its likely that I missed a ground since I wasnt the one who tore the engine down. However is it possible that for my scan tool to jump these 2 grounds together? Gonna try and jump the grounds at the connector tomorrow or better yet I might just ground the shared ground at the dlc. Any input/advice welcomed!

It's absolutely possible for your scan tool to be completing a path between pins 4 and 5 at the DLC. Not all scan tools are designed this way, but most are. Ohm check between those two male pins on the scanner cable if you want to prove it.

I've seen this as well, most recently on a Ford Probe with a corroded PCM ground. Would run all day with the scanner in it, but never without. :silly:

Shorting 4 and 5 at the DLC together would probably be easiest? But I'd still suggest tracking it down, just for peace of mind. By bridging them, you may end up putting too much load on the working ground.

So pins 4 and 5 aren't used here... however 12 and 13 are the 2 grounds. I'm gonna bridge them today and see if it starts if so il work back wards from their checking ground integrity.

This might be obd 1.5

Obd 2 conector pinned out with obd 1

Some car makers did this inbetween 95 and 97 so double check this as pin 4 and 5 are grounds in obd 2 but not in obd 1.5.

Yal were right, pins 4 and 5 are grounds. Nothing was in 12 and 13. Kinda makes you question wiring diagrams now lol. However it turned out to be a disconnected ground, I recieved the car broken down to the head with the intake having nothing connected to it, this ground went to the intake. I ran a jumper between pins 4 and 5 and car started. Turns out pin 5 was open and was the shared ground with pgmf1 relay. Thanks for the help guys. I will post a pic of the disconnected ground, you can barely see it, even more so in the pic.

Good job those little boogers are hard to see when they match all the dirt lol.. congrats

You know, I've seen wiring diagrams for DLC's do that occasionally. I don't think it's a diagram translation problem, either. I got this out of the OE diagrams:



I'll give Honda a pass on this one, 'cause this was the early days of OBDII. :silly:

Well done on the fix. Putting something back together after someone else tore it apart is never a good time.

Thanks guys, I've came along way with my diag (I'm still lacking alot) since finding scanner danner. I was pretty proud of myself

Thrashnasty13 wrote: Thanks guys, I've came along way with my diag (I'm still lacking alot) since finding scanner danner. I was pretty proud of myself

You should be. Many techs would have replaced the PGM-FI relay two or three times, replaced the PCM, then given up.