checks2rex

'93 Chevy Van G-20...5.7 liter...273,000 miles...Anti-lock brake light has started coming on just as van seems to lose power...speedometer will not function and vehicle acts as if tranny is slipping...Just changed tranny ATF and filter...no help...Ideas? Thx...

checks2rex

My 1993 Chevy G-20 Van 5.7 liter automatic has been running great (273,000 miles) until recently when it simultaneously lost power as the anti-lock light came on...feels as if the transmission is slipping...at same time, spedometer stops functioning...Can anyone pin-point the problem? We have already changed the ATF and Tran filter...Is this an electrical issue? I cannot drive the vehicle as-is...Many Thx for any advice...RB

comeback

I have a 98 Chevy g20 van with a 5.0L. The speedometer started to read inaccurate then all of a sudden it would either read double the mph that I was traveling or nothing at all. The anti lock brake light would come on as well. The fix for the problem cost me $145, but I spent a couple months diagnosing. The first two things to check are very simple all you need is a multi meter an 8mm socket and a 10mm socket. First remove the VSS located on the passenger side of the transmission tail shaft (one 8mm bolt). Hook a multi meter up to the prongs where the wiring harness would connect. Set the multi meter for AC voltage. drag a tool, piece of metal it doesn’t matter across the magnetic end of the VSS. if you get a AC voltage reading put it back in the transmission. Move onto the computer, it can be removed with a flathead screwdriver and a 10mm socket. First remove the three 10mm bolts found on the air box. Leave the hose clamp that connects the air box to the intake boot alone . Remove the 4 plugs that go into the computer and the two clips that hold the computer (using the flathead screwdriver helps). Remove the computer (when removing, move the airbox to the passenger side of the vehicle this will give you just enough room to get the computer out of the engine compartment), flip it over and remove the two allen head screws on the bottom. Remove that small cover and look inside, if you see what looks like corrosion, or battery acid. The computer has gone bad. You need to buy another and have it reprogrammed by your local dealer (the vehicle will not run if you try to install the new computer w/o reprogramming.). If no corrosion and everything looks good reinstall the computer and begin continuity checks from VSS all the way to the computer. Also check all grounds. I have been told by a mechanic at the dealership that almost always the computers go bad not the VSS. A certain chemical used in the capacitors breaks down after so many hours of run time and leaks out onto the motherboard destroying every connection it comes into contact with. Hence why your problems will be erratic and slowly get worse.

RacerX

Yea, sounds like a bad Vehicle Speed Sensor. Like the guy said above, it is in the tailshaft of the transmission accessible on the driver side. In the olden days they were mechanical, but these days are all electronic.