Chevy & GMC Vans

So over the weekend we drove down to a friends house about 4 hours drive away.
We've had the abs and brake lights coming on since we bought the van about 1000 miles ago.
When braking to a stop, like a surprise red light while going 60 down a dual carriageway, the brake seems to pulse like a warped rotor if the abs and brake lights are on.
Just this weekend the speedo cut out as we were cruising down the highway, when that went out, so did the abs and brake lights as well as the cruise control.
Occasionally after a bump the speedo came back but would soon go off again. I noticed braking to be smoother when stopping at a light from speed when the speedo was out..

It's like there's a faulty connection somewhere as the speedo comes and goes.

We've done some reading from various sources online but have not found a definitive answer as to what causes the speedo to go out. We had thought the abs and brake lights were due to the brake control module having faulty solder like so many people have experienced but I couldn't fix that due to a stripped out bolt. Perhaps it also has to do with whatever is causing the speedo to cut out??

The Mrs is supposed to be doing a roadtrip down Route 66 this coming weekend and I'd prefer she didn't get any tickets. (She could use the gps I suppose.)
Has anybody got any info. as to what is causing this? and how I can fix it.

Check the rear VSS speed sensor (and wiring) on the transfer case. There are three of them, one for front propshaft, one for rear propshaft and the rear VSS supplies rear wheel speed to PCM which is used by EBCM (abs computer), TCCM (transfer case module) and also for speedo. Could be a relatively simple fixaroo. All three sensors on the transfer case are the same so you could try swapping it with one of the others to see if the speedometer issue goes away.

It's #3 on the transfer case:



As for the ABS/brake lights and bad EBCM, you really need to try to get that screw out so you can repair it! Since it's stripped I would try attacking it with a Dremel and grinding bit. Perhaps a 90° adapter or even right angle drill as they are not that expensive anymore.

I've bought a new speed sensor so I'll try that this weekend. Thanks for the diagram, that should make it easy.

I put a new sensor in Friday night. The Mrs went on a mini roadtrip Saturday morning, drove about 400 miles with ni issues.
She then teied putting the cruise control on and the speedo stopped again. Argh, I thought we fixed it.

Any further ideas?