Vehicle Speed Sensor "B" Circuit Low
The powertrain control module detected a low input signal from Vehicle Speed Sensor B, which provides critical speed data for transmission control, ABS, and traction systems. This electrical or mechanical fault must be addressed promptly as it can cause transmission and ABS malfunctions.
What You Might Notice
- Erratic speedometer or odometer operation
- Irregular or harsh transmission shift patterns
- Service engine soon lamp illuminated
- Traction control lamp illuminated
- Antilock brake lamp illuminated
Most Common Causes
- 1
Faulty Vehicle Speed Sensor B
The speed sensor itself has failed electrically or mechanically, no longer sending proper signal voltage to the PCM.
- 2
Wiring or connector issues
Corroded, loose, or damaged wiring harness or connectors to speed sensor B causing intermittent or low signal.
- 3
Low sensor power supply voltage
The PCM is not supplying adequate voltage to the speed sensor due to a power circuit fault or relay failure.
- 4
PCM or module malfunction
The powertrain control module itself may be defective and unable to properly register the speed sensor input signal.
How to Diagnose It
- 1
Check Faulty Vehicle Speed Sensor B — The speed sensor itself has failed electrically or mechanically, no longer sending proper signal voltage to the PCM.
- 2
Check Wiring or connector issues — Corroded, loose, or damaged wiring harness or connectors to speed sensor B causing intermittent or low signal.
- 3
Check Low sensor power supply voltage — The PCM is not supplying adequate voltage to the speed sensor due to a power circuit fault or relay failure.
- 4
Check PCM or module malfunction — The powertrain control module itself may be defective and unable to properly register the speed sensor input signal.
How to Fix It
- 1
Inspect and test Vehicle Speed Sensor B
Locate sensor B (typically on transmission output), test voltage output with a multimeter while driving, and replace if voltage is below specification or absent.
- 2
Check wiring and connectors
Inspect the wiring harness and connector to speed sensor B for corrosion, loose pins, or damage. Clean connectors with electrical contact cleaner and ensure all connections are tight.
- 3
Verify sensor power supply
Test the power and ground circuits feeding the speed sensor with a multimeter to confirm proper voltage is available. Check for blown fuses or failed relays in the sensor circuit.
- 4
Reprogram or replace PCM if needed
If all sensors and wiring test normal, the powertrain control module may require reprogramming or replacement. Consult factory diagnostics to confirm PCM fault.
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