Speedometer won't work in 97 Astro, replaced sensor..help
What sensor ? VSS - vehicle speed sensor on the transmission ? Colud be the speedometer gauge is bad . Do you know how the insturment cluster get's that info. ? Your best bet , take it to a qualified repair shop . You have no idea how it works , don't have the diagnostic tool's to find the problem ,so do yourself a favor . The first step would be to hook up a factory or professional type scan tool to see if the VSS info is seen in the VCM ,then to see what the VCM is sending over the serial data network . Do you know what a serial data communication network is ? VCM is vehicle control module .
Speedometer and Odometer Circuit Description
An electronic speedometer is standard equipment on all models. Integrated circuits control the air core speedometer and the stepper motor odometer. Removable bulb and socket assemblies provide the lighting. The socket assembly inserts into the back of the instrument cluster.
The speedometer system consists of the following components:
• The instrument cluster
• The vehicle speed sensor (VSS) calibrator
• The VSS
• The related wiring
The VSS calibration is part of the VCM that changes the analog output from the VSS to a digital signal. The digital signal contains 4000 pulses per mile (PPM) for the instrument cluster. The VCM sends the signal to the speedometer through CKT 389. The VSS calibration matches to the final drive and the tire size of each vehicle. Reprogram the VCM with the proper VSS calibration if the final drive or tire size changes for any reason. The signal will not be accurate for the proper speedometer/odometer operation if the necessary change is not made. An incorrect VSS calibrator can also affect the following components:
• The antilock brakes
• The vehicle control module (VCM)
The cruise control systems
The VSS calibration is programmed into the VCM. Do not service the VSS calibrator separately.
The VSS is a permanent magnet signal generator that sends an analog signal proportional to the propeller shaft speed to the VCM. The VSS mounts to the transmission tailshaft extension housing on the two-wheel drive model. The VSS mounts to the transfer case output shaft housing on the all-wheel drive models.
Use a Scan Tool in order to read the vehicle control module (VCM) diagnostic trouble codes.
Are there any vehicle speed sensor related trouble codes?
Testing an not guessing fixes problems
Sep 19, 2017 |
1997 Chevrolet Astro