Strange Speedo / RPM / Trans problem

craigix · #1 10-28-2005, 04:45 PM

Just had my full size dually 1999 7.4 classic dropped off by the garage and its came back with a weird fault it didn't go there with:

The speedo and RPM are not working, and the trans won't change above first gear.

No blown fuses. No check engine light. All other electrics working fine.

The garage is not open until monday now, I'm hoping this is just a case of them not reconnecting something and I can fix it myself, but since its dark now I thought I'd ask for some ideas of what it could be.

Any help? It would save me a lot of time.

Thanks,

Craig

2000CAYukon · #2 10-28-2005, 06:38 PM

The speedo and tranny need a functional speed sensor (at the tranny) to work properly. That would be the first thing I would check.

Not sure about the tack though.

//2000CAYukon

craigix · #3 10-29-2005, 09:17 AM

Thanks, I'll check that now.

Just noticed that also the trip isn't working either and the PRND321 does not light up.

Stranger and stranger.

-Craig

maxwedge · #4 10-29-2005, 09:37 AM

What was done by the garage, any connection here. The symptoms can pont to an ign switch or a main power circuit to it disabled.

craigix · #5 10-29-2005, 10:29 AM

They were giving it a large service (100,000 mile service). I did ask that they check everything, so I think a lot of things are going to have been opened up and removed and put back and such.

Is there someone with a workshop manual who could pinpoint whats not working or hooked up correctly? Driving me mad. I am slowly going through each area on the engine bay just checking for obvious things, but its like a needle in a haystack at the moment.

Thanks for all the help,

Craig

2000CAYukon · #6 10-29-2005, 12:44 PM

Is this the new body style or the old? I have manuals for the 2000 model year and if you have the new body style, it might be the same.

//2000CAYukon

craigix · #7 10-29-2005, 01:45 PM

Its the old shape, 7.4

Still no progress here

everything looks fine. Argh.

maxwedge · #8 10-29-2005, 02:14 PM

You need a wiring diagram, to check for current feed out of the ign switch to these functions, one is a subscription to alldata.com or get a pro to look a it for you.

craigix · #9 10-29-2005, 03:14 PM

yep, looks like its going to be going back for a day or 2 now. Yet I am sure it is all down to one thing not being connected. Oh well. Was worth a try

Thanks Everyone, but you know, if you think of anything, do post I still have sunday!

troy1 · #10 10-30-2005, 12:46 AM

I would take a look at the Ignition switch it will cause an inop. tach, shifting problems and various other complaints. have them check voltage at the trans fuse.

Jeremy-WI · #11 10-30-2005, 07:06 AM

If they find voltage at trans fuse, have them check for voltage at the tranny connector and check for bent pins there. There is actually a TSB from GM about this problem, but I don't remember the number

craigix · #12 11-02-2005, 05:32 PM

Just for closure this was indeed a power issue, all fixed and collected today, but the battery has been off and the radio is locked! Oh well, at least it is back on the road!

2000CAYukon · #13 11-02-2005, 08:30 PM

Quote:

Originally Posted by craigix

Just for closure this was indeed a power issue, all fixed and collected today, but the battery has been off and the radio is locked! Oh well, at least it is back on the road!

Where exactly was the power issue? Battery, ignition switch, tranny?

Thanks,
2000CAYukon

craigix · #14 11-03-2005, 02:41 PM

They just said it was 'electrical' so i'm guessing they left something unplugged or had damaged a wire. I didn't press them on it as it was working, there was no charge and I just wanted to get going.

Alas it still isn't running quite right so time to replace even more parts! Seems to vibrate and stutter around 40-50mph and the power just isn't what it was. Think i'll be placing a large parts order, got to get this thing perfect for winter!

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