speedometer wiring for 01 5.3 into 91 gmc k1500

just finishing swapping a 01 5.3/4l60e into my 91 gmc 1/2 ton

being a 91 the truck has its drac/vssb built into the cluster (not in a seperate white box)

meaning that the cluster expects to see the ac waveform from the 40 tooth reluctor wheel in the tranfercase

the problem is that the 411 pcm also expects an ac waveform from the 40 tooth reluctor wheel

connecting both to the same vss sensor results in neither receiving the signal


is there a solution to my problem (besides swapping speedometers I consider that a last resort)

Believe it or not, you should be able to split the signal between both items.
If you wire it in and they don't work, then switch the wires going in to one of the 2 (either ECU or speedo) and see if that doesn't fix it. I know polarity shouldn't matter, but I think you'll find that it should work.
Worst case, you may need a module from Dakota Digital or something to run the speedo.

I'm curious on this one too. I had my 89 up on the rollers and had to switch it into higher gear to get tuned but would like to tackle this issue. Does anyone have a pinout handy for the cluster? At this point I don't even care, it's more important that the transmission works right...I just dont know the wiring pinout so I don't even know where to grab the VSS signal from

Here is what I did on my swap. There are two wires coming the original VSS on the 700r4. One is Yellow (400 High) and the other one is Purple (401 Low). I spliced them to the LS1 pcm Purple/White (821 High) and Light Green/Black (822 Low). That got it working. Are you doing an LS1 or another Gen III/IV engine. If so the colors may be different. Hope this helps.

Personally I am doing a 2000 5.3...I DO have the complete pin out for the ECU so that is not something I am worried about...I AM wondering where you ran the wires from/to and how did you keep your gauge operational? DID you tap into the existing wires leaving the gauge wiring intact? OR did you just say screw the speedo? OR did you do something else?

i will know later this weekend if swapping the polarity works (I've been to busy to work on my truck)

twisted454

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I AM wondering where you ran the wires from/to and how did you keep your gauge operational

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oil pressure sender just works i connected the brown wire from c100 in the 5.3 harness to the wire going to the drivers side bulkhead

tach works after changing settings in computer to 3 (high and low) and connecting the output wire (AT C100) to the white wire in the connector inside the pass side dash

the coolant temp sensor you need a 3 wire sensor out of a 98 firebird and to rewire it to the 2 wires in the 5.3 harness and the third wire connects to the truck

volt gauge just works (I taped up my alternator control wire so the warning light is off as I prefer pcm alternator control)

there is a bunch more info on the site if you search for it but if you get stuck on a wiring/computer issue feel free to pm me i run a 2 bay garage (have access to wiring diagrams/pinouts)

Thanks for the passing on of the information...I appreciate the input...fortunately, the rest of the gauges I had working properly but I honestly and truly appreciate the fact that you took the time to try to help out. The GOOD news is that I put the truck up on the lift and decided to try CPWire and Chevy's suggestions

Yellow/Purple from transfer case pick up routes to engine bay which tied into my main harness...from there I simply tapped into that signal. My ECU is a 2000-2001 circa truck ECU so the pin out is on red brick, 20 and 21 pins. Chevy IS in fact right on the money as to which colors the wires are. I simply tapped the ECU into those wires. The ECU only monitors that signal for speed information, it doesn't appear to draw anything from it because the ECU now sees tailshaft speed AND the gauge still works. My seat of the pants impression is that the gauge is still reading correctly too...that being said, I will leave that final analysis for when I put the truck back on the dyno to double check.

So...thanks everyone for the input...hopefully this helps someone in future. My only concern is, according to my harness book, that 1999 ECU's don't have the same pin out and I am unable to determine the hi signal input to the ECU so if you have a 1999 ECU, this might not be the definitive answer...but it appears that post 99 ECU's should be good to go.

This is great info. I'm swapping an 05 5.3 into and 88 C1500 right now. Hopefully all the gauges work properly for me when I'm done.

Glad this helped. Took the truck out for a test drive this evening...looks like all the bugs are worked out. I will be doing a write up shortly...there are a lot of helpful things I learned that are different from the TBI trucks to the newer models

finally got my speedo working wired as suggested i tried everything with no luck and finally swapped to a different cluster i had laying around then it just worked :)

evidently my cluster let the magic smoke out at somepoint (trucks been sitting for a year or so)

now i need to finish my efan wiring and drive it some (drove it fifteen miles last night & filled it up with premium. trying to add some octane to the half tank of year old gas)

now it needs tires nothing like square 285/75/16 bfg's

HAHAHAHA...Yeah, my tires are pretty flattened out at this point too after sitting for a year...lol...good news is I have a single wiring issue with a fan relay to tackle and this is DONE. I put the truck back up on the rollers yesterday, and did some final street tuning...had to lean out the idle a bit but other than that...speedo and ECU were good for speed signal and looks like the registered speed at the gauge was as good as it always was...probably a tire thing because it always registered a little faster than actual.

got my efan wiring done and balanced my square bfg's (23 OZ TOTAL!)

drove it another 15 miles before my transmission blew :( lost 3rd and 4th

the good news is that it was still under warranty (bought from local salvage yard with 90 day warranty)

and they supplied another one and extended my warranty to 6 months

this time i'm having my trans guy go thru it (master kit,beast sun shell and 29 tooth sprag) no need to build it any better than that and the 5.3 is stayin stock and I don't tow anything

going to see if this helps me, I've got a 1997 GMC with a 2000 4.8l swap. I've driven it a total of two miles....no speedo or trip working. The ABS is on as well. Now that being said, the speedo sensor was "Y'd" to both the OBS ecu and the NBS ecu. Supposedly, the signal was split in order for new ecu to run shifting duties and the old ecu to deal with gauges.

Any suggestions