Speed sensor took a crap?

[sy2206]

I think my speed sensor took a crap on me. I don't have my laptop yet, so I can't put datamaster on it. Anyway, my speedometer, odometer, and cruise control just stopped working. On top of that, when I pull up to a stoplight, it wants to die on me, and has actually stalled a couple times. I know most cars have a higher idle speed when the ECU see the car is still moving, then once it comes to a complete stop, it idles down a couple more hundred RPM. So I'm thinking the speed sensor is bad, and is reading zero all the time. That would cause these symptoms. If I had my DM up and running, I could just drive and watch the vehicle speed, but my laptop hasn't got here yet....

Any input?

 

[sy2206]

Re: Speed sensor took a crap?

Hey Dave,
I checked all the fuses, they're fine. I was hoping to have my datamaster up and running by now, but the "New" laptop that I bought wasn't even close to new, so I had to send it back. I'll have to see if I can get my friends scan tool on it, that should show vehicle speed. I'm really thinking it's the speed sensor...

 

[turbodig]

Re: Speed sensor took a crap?

Check the blue wire on the DRAC. It's short and gets pulled out easily.

 

[BoostedSUV]

Re: Speed sensor took a crap?

^x2. Had this happen to me. I had to solder the blue wire back to the DRAC. From moving ecu around it must have pulled out. Check there first.

 

[sy2206]

Re: Speed sensor took a crap?

Short ALDL pins A&B. Turn on key. Watch check engine light. If you see code 24, you have a VSS issue. If you don't see code 24, the VSS and DRAC are functioning, and it's in the speedo, cluster, or wiring.

If you have Code 24: Block the car up so you can put it in L1 gear and let the tires spin. With an AWD all four must be off the ground.

Put your VOM on AC volts. Put the probes on the pur and grn wires at the DRAC. You should see a fluctuating (pulsing) AC voltage. If you don't, you have a bad VSS or wiring.

If you have access to another sensor, go for it. But new ones are over $100.00. I'm trying to help you be sure you really need one, rather than test by substitution. I've never had one go bad. Wiring, yes. VSS sensor itself, no.

No Datamaster, Laptop, or Scan tool required.

The blue wire at the DRAC seems fine. There are no visible breaks or damage. So I took a paperclip and jumpered pins A and B, and all I get is a code 12. So I get out the VOM, put it between the purple and green, and I get nothing. Swapped out the DRAC module for another one I have here, and it did the same thing.

So voltage would point towards VSS, but there's no code?

 

[sy2206]

Re: Speed sensor took a crap?

Ok, I'm pretty sure I've got it figured out now. I went out to look things over again real good, and when I moved the harness on the VSS, the green wire broke. I barely even touched it, so I'm sure the wire itself was broke, just a little piece of the coating was holding it togather. Looks like I'm off to the junkyard to get a pigtail....

Solder that on and I think I'll be good to go.

 

[turbodig]

Re: Speed sensor took a crap?

Ok, I'm pretty sure I've got it figured out now. I went out to look things over again real good, and when I moved the harness on the VSS, the green wire broke. I barely even touched it, so I'm sure the wire itself was broke, just a little piece of the coating was holding it togather. Looks like I'm off to the junkyard to get a pigtail....

Solder that on and I think I'll be good to go.

Drac uses the same terminals the ECM does, if I remember right.

 

[sy2206]

Re: Speed sensor took a crap?

Not sure what the deal is here. Based on your next post, it seems there should be a code 24. Perhaps the battery has been disconnected since the last time you drove it?

How'd I do? I didn't think it was going to be the Sensor itself.

That 18" "extension harness" is SyTy only. You're not going to find one in a wrecking yard. You didn't say which wire broke, but if the one on the main harness is OK, but won't 'reach', extend it with some wire. Easy enough to do. If originality is important, I have one of those harnesses around here somewhere. Let me know, and I'll start digging.

Glad to see you've made some progress.:tup:
Dave

LOL, yeah, you hit it dead on! The wire broke within 1/4" of the connector(sensor). To be honest with you, I didn't even crawl under there too far, I don't have the truck up on stands yet. I didn't know there was an extension harness. From the sounds of it, what you're saying is there's a plug on the harness, which doesn't reach the speed sensor, so they made an extension cable to lengthen it? I'm not concerned with 100% originallity. If thats the case, I'll probably cut the first plug off the harness and just solder in an extension cable. I have some of that good OEM heat shrink(with the sealer in it) so I think I'll just lengthen it up, solder them up, use the good heat shrink, loom it, and call it good!

 

[sy2206]

Re: Speed sensor took a crap?

Ok, I got uder there this morning. There is no extension harness, so that must be a Bravada only thing, or maybe some Ty's had it? I'm not sure, but my truck definately doesn't have it.

Incase anyone else runs into this in the future, GM sells a connector package for the speed sensor. It's part number 12085498, $33 list. Au-ve-co also has the harness(they probably make it for GM). The Au-ve-co part number is #16694. This same plug is used for the AWD transfer case speed sensor(Sy, Ty, Astro van, Bravada) and many cornering lamp and fog lamp applications on GM cars also. I went to the junkyard and got the exact same harness off a mid 90's Caddilac front cornering light.

I'm going to go solder this on and see how it works....

 

[sy2206]

Re: Speed sensor took a crap?

Soldered my new harness on the end, and it works great! Speedo, cruise, odometer all work great, and it doesn't die everytime I roll up to a stop.

Thanks Dave!

 

[gkrcr882]

Re: Speed sensor took a crap?

Good to hear. I actually had the unfortunate luck of tracking down a low-reading speedometer and non-functioning odometers to a bad gauge cluster itself. Swapped in one purchased from another member here, and all is good. Even switched over the fuel/oil/temp/volts cluster and they function better. Just food for thought, the gauges themselves can and do go bad! :2cents: