Code
C00A500
BYD
C — Chassis
Rear left wheel-speed sensor signal line short to UBATT
Views:
UK: 5
EN: 13
RU: 10
AI status
Completed
Completed
100%
Causes
- Chafed or pinched signal wire contacting a battery-positive conductor or fused power feed
- Corroded or damaged sensor connector with battery-voltage feedback
- Faulty wheel speed sensor with internal short to supply
- Aftermarket/previous repair wiring routed incorrectly and tied into a 12V feed
- Short inside ABS/ESC control module (less common)
- Water intrusion or corrosion at connector creating a conductive path to power
Symptoms
- ABS and/or traction/stability warning lamp illuminated
- Loss or reduction of ABS/ESC functionality for that wheel
- Erratic or no speed reading for rear-left wheel in scan tool live data
- Possible speedometer or cruise control faults if vehicle derives speed from ABS sensors
- ABS pump/valve cycling or limited braking intervention depending on system logic
What to check
- Read and record freeze-frame and live data with a scan tool; note rear-left wheel speed value and compare to other wheels
- Visually inspect sensor, connector and wiring from wheel hub to chassis and to ABS module for damage, corrosion, kinks or pinching
- With ignition ON (engine OFF), back-probe the sensor connector and check for battery voltage on the signal pin
- Disconnect the wheel sensor at the harness and check voltage at the harness side to determine if short is in sensor side or upstream
- Measure resistance/continuity between the signal wire and battery positive and between signal wire and module pins to locate the short
- Wiggle test harness while monitoring live data/voltage to reproduce intermittent shorts
Signal parameters
- There should not be a constant battery voltage (≈12 V) on the wheel speed signal line at rest or while rotating
- Passive (magnetic) sensors: near 0 V at rest, generate AC pulses proportional to wheel speed when rotated
- Active (Hall/effect) sensors: typically produce 0–5 V square/pulsed signal referenced to ground; pulse frequency increases with speed
- Pulse frequency and amplitude should correlate with vehicle speed and match other wheel sensors
Diagnostic algorithm
- Connect a scan tool and confirm C00A500 is current; capture live wheel-speed values and freeze-frame data.
- Visually inspect rear-left sensor, mounting, and harness routing for obvious damage, corrosion, or pinch points.
- With ignition ON (engine OFF) back-probe the sensor harness connector signal pin: if ~12 V is present, proceed to step 4. If not, inspect sensor for open/short to ground and test sensor output while spinning the wheel.
- Disconnect the wheel sensor at the harness. Recheck voltage at the harness connector. If battery voltage remains, the short is upstream (harness or module). If voltage disappears, the sensor is likely internally shorted—remove and bench-test/replace sensor.
- If voltage persists on disconnected harness, trace the harness toward the ABS module: unplug intermediate connectors, inspect factory splices, and check for contact with battery-fed circuits or chafed areas touching bodywork or a power feed.
- Measure continuity between the signal wire and battery positive to pinpoint section of short. Use a multimeter and isolate segments by disconnecting connectors to localize.
- If harness and connectors intact, disconnect the ABS/ESC module connector and check whether the short disappears. If short remains only when module connected, suspect internal module fault—verify with manufacturer guidance before replacing.
- Repair: replace/repair damaged wiring or connector, replace sensor if internally shorted, or replace control module only after confirming the harness and sensor are good.
- After repair, clear codes, perform a road test while monitoring wheel speed readings to confirm proper operation and that C00A500 does not return.
Likely causes
- Damaged/chafed harness at suspension, body harness chafe point, or near wheel arch
- Corroded/contaminated sensor connector (moisture ingress) causing high voltage on signal pin
- Failed wheel speed sensor with internal short to its supply conductor
Fault status
Status
Rear-left wheel speed sensor signal circuit shorted to battery positive (UBATT). ABS/ESC module detects abnormally high voltage on the signal line, preventing valid wheel-speed input.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
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