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John, Master A.S.E Automotive technician
Category: Chevy
Satisfied Customers: 9176
Experience:  A.S.E MasterTechnician A1-A8 w/L1,38 years experience General Motors Master Technician
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1998 Chevy Express 1500: van..5.7l V-8 w/170,000m..speedometer

Customer Question

My father has a 1998 Chevy Express 1500 conversion van, 5.7l V-8 w/170,000m. The speedometer started reading approx. double actual vehicle speed and the anti-skid light illuminates. Since this has happened the van will not go above 30mph (approx) and you can hear the engine does not go above 1500-2000 rpm. I changed the vehicle speed sensor to no avail other than it took about a half mile more before the anti-skid light came on. Braking appears to be normal to me as I do not drive this vehicle often. I was also under the van searching for the location of the wheel speed sensors and found the ones on the front wheels but found no wiring or evidence of sensors on the back.
Submitted: 8 years ago.
Category: Chevy
Expert:  John replied 8 years ago.


You should have the computer system scanned for failure codes & check the data of the vehicle speed sensor (for powertrain computer) to see is it is actual value.The ABS uses wheel speed sensors (mounted at front brakes & in the rear axle housing for the rear).If certain codes are set in the computer & the van has TAC (throttle actuator control-computer actuates throttle control) this can keep the vehicle from accelerating.If not it sounds like you may a plugged catalytic converter.

Customer: replied 8 years ago.
I have used a OBD II reader on the vehicle and no codes were given. I used this through the main connection under the dash. Would a service station be able to pull codes that the reader would not? Granted my reader is not the high end variety and I am not sure if after-market readers only read codes if the check engine light is tripped.
Expert:  John replied 8 years ago.
What you need to see is vehicle data from the computer & code readers only access the PCM,you need to view the EBCM for the brake data.A service station with a good scan tool can do this ,not any service stations around like that where I live.You will need a service center with someone that knows what they are doing.