Vehicle Speed Sensor "A" Range/Performance

What it means

The vehicle speed sensor (VSS) is sending a signal that is electrically valid but does not make sense compared with other sensors. The vehicle speed sensor (VSS) reports road speed to the ECU, transmission, speedometer and cruise control. This usually points to a sensor that is reading wrong, or to a real mechanical problem it is reporting correctly, rather than a broken wire.

Symptoms

• Check engine light on
• Speedometer not working or erratic
• Harsh or late automatic shifts
• Cruise control not working
• ABS or traction light on (if wheel sensors are used)

Probable causes

Most likely first

1. 1Damaged sensor drive gear or tone ring
2. 2Wrong tyre size fitted
3. 3ABS wheel speed sensor fault feeding bad data
4. 4Failing sensor giving an inaccurate reading
5. 5Poor connection at the sensor connector

How to diagnose it

Work through these in order before buying parts

1. 1Record the code and its freeze frame data (speed, load, temperature when it set), then clear it and see if it comes back.
2. 2Inspect the vehicle speed sensor (VSS) connector and wiring (on the transmission output, or the ECU uses the ABS wheel speed sensors). Look for corrosion, bent or pushed-back pins, oil contamination and chafed insulation.
3. 3Watch the vehicle speed sensor (VSS) reading on live data. Compare vehicle speed on the scan tool with GPS speed while driving. It should match closely.
4. 4Compare the vehicle speed sensor (VSS) reading against related sensors and the real-world condition. If they disagree, find out which one is telling the truth before buying parts.
5. 5If the wiring checks out, test the sensor itself against the specification in a service manual.
6. 6Check for technical service bulletins (TSBs) or software updates for your make and model; some codes have known factory fixes.

Common fixes

• Fix the underlying problem the sensor is reporting, if real
• Replace the vehicle speed sensor (VSS) if it reads wrong against a known-good reference