Code
C0237
Generic
C — Chassis
Left Front Wheel Speed Sensor Circuit Fault
AI status
Completed
Completed
100%
Causes
- Damaged or disconnected wheel speed sensor wiring or connector
- Corroded or contaminated sensor connector pins
- Damaged or faulty wheel speed sensor (Hall or passive tone sensor)
- Physical damage or misalignment of the tone ring/reluctor (missing teeth, heavy rust, debris)
- Short to power or ground in sensor circuit
- Faulty ABS/traction control module or poor module ground
Symptoms
- ABS warning lamp illuminated
- Traction control or stability control warning active
- Possible loss of ABS/traction control functionality
- Speedometer may show erratic behavior on some vehicles
- Possible intermittent behavior related to steering or wheel movement
What to check
- Read ABS and body control module codes and freeze frame data with scan tool
- Visual inspection of left front sensor, wiring harness, and connector for damage, corrosion, and contamination
- Check wheel bearing and hub area for loose components or excessive play
- Inspect tone ring/reluctor for missing teeth, cracks, heavy rust, or debris
- Wiggle test wiring while monitoring live wheel speed data for intermittent changes
- Measure resistance and/or output signal of sensor with multimeter or oscilloscope
Signal parameters
- Passive (magneto) sensor: AC voltage increases with speed; low speed generates small mV, higher speeds up to ~1–2 VAC depending on vehicle
- Active (Hall/electronic) sensor: digital square-wave output; typically 0–5V or 0–12V switching between reference and ground
- Expected resistance (passive type) commonly ~800–2000 Ω (vehicle-specific — consult manual)
- Reference/supply for active sensors typically 5V (some systems use 12V); verify with vehicle data
- Signal frequency: increases with wheel speed; expect a clean, consistent waveform on oscilloscope (roughly 10s–1000s Hz depending on speed)
- Duty cycle often near 50% for active sensors; look for missing pulses or irregular amplitude
Diagnostic algorithm
- Connect a scan tool. Read and record trouble codes, pending codes, freeze frame data and live left front wheel speed sensor values.
- Perform visual inspection of left front wheel area: sensor, tone ring, hub/bearing and wiring harness. Address obvious damage or debris first.
- With ignition ON (engine off), disconnect sensor connector and inspect pins for corrosion, bent pins, or water intrusion. Clean and reconnect or replace connector as needed.
- Check reference voltage and ground at the sensor connector for active sensors: backprobe connector with key ON. Verify supply voltage (typically ~5V) and good ground.
- Measure sensor resistance (passive type) across sensor leads with multimeter. Compare to vehicle spec. Replace sensor if open or out of spec.
- With wheel lifted and safe supports in place, spin the wheel and observe sensor signal using an oscilloscope or multimeter AC mode: passive should produce AC waveform; active should produce switching waveform. Look for missing pulses, low amplitude or noise.
- Perform continuity and short-to-power/ground checks on the wiring from the sensor connector to the ABS module connector. Repair any open or shorted wiring.
- Wiggle test the wiring and connectors while monitoring live data or scope to reproduce intermittent faults. Repair chafed/broken wires and secure harness.
- If wiring and sensor check good, inspect tone ring closely; replace or repair if teeth are damaged or air gap excessive. Correct air gap to spec.
- If sensor, wiring, and tone ring are good, consider module fault: verify other wheel sensors operate normally and, if suspect, test/replace ABS module per service manual.
- After repairs, clear codes and perform a road test while monitoring left front wheel speed data to confirm proper operation and that code does not return.
Likely causes
- Connector corrosion or loose connector at left front sensor
- Open or shorted wiring between sensor and ABS module
- Failed left front wheel speed sensor
- Tone ring damage or excessive air gap
Fault status
Status
Left front wheel speed sensor circuit fault detected — signal out of range, missing, open or shorted. This may disable ABS/traction control for the affected wheel until corrected.
Repair difficulty: Medium
Diagnostic time: 0.5-2 hours
Similar codes
Repair manuals
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Code
C0237
HUMMER
C — Chassis
Right Rear Ride Height Sensor Circuit Range/Performance
AI status
Completed
Completed
100%
Causes
- Damaged or disconnected wheel speed sensor wiring or connector
- Corroded or contaminated sensor connector pins
- Damaged or faulty wheel speed sensor (Hall or passive tone sensor)
- Physical damage or misalignment of the tone ring/reluctor (missing teeth, heavy rust, debris)
- Short to power or ground in sensor circuit
- Faulty ABS/traction control module or poor module ground
Symptoms
- ABS warning lamp illuminated
- Traction control or stability control warning active
- Possible loss of ABS/traction control functionality
- Speedometer may show erratic behavior on some vehicles
- Possible intermittent behavior related to steering or wheel movement
What to check
- Read ABS and body control module codes and freeze frame data with scan tool
- Visual inspection of left front sensor, wiring harness, and connector for damage, corrosion, and contamination
- Check wheel bearing and hub area for loose components or excessive play
- Inspect tone ring/reluctor for missing teeth, cracks, heavy rust, or debris
- Wiggle test wiring while monitoring live wheel speed data for intermittent changes
- Measure resistance and/or output signal of sensor with multimeter or oscilloscope
Signal parameters
- Passive (magneto) sensor: AC voltage increases with speed; low speed generates small mV, higher speeds up to ~1–2 VAC depending on vehicle
- Active (Hall/electronic) sensor: digital square-wave output; typically 0–5V or 0–12V switching between reference and ground
- Expected resistance (passive type) commonly ~800–2000 Ω (vehicle-specific — consult manual)
- Reference/supply for active sensors typically 5V (some systems use 12V); verify with vehicle data
- Signal frequency: increases with wheel speed; expect a clean, consistent waveform on oscilloscope (roughly 10s–1000s Hz depending on speed)
- Duty cycle often near 50% for active sensors; look for missing pulses or irregular amplitude
Diagnostic algorithm
- Connect a scan tool. Read and record trouble codes, pending codes, freeze frame data and live left front wheel speed sensor values.
- Perform visual inspection of left front wheel area: sensor, tone ring, hub/bearing and wiring harness. Address obvious damage or debris first.
- With ignition ON (engine off), disconnect sensor connector and inspect pins for corrosion, bent pins, or water intrusion. Clean and reconnect or replace connector as needed.
- Check reference voltage and ground at the sensor connector for active sensors: backprobe connector with key ON. Verify supply voltage (typically ~5V) and good ground.
- Measure sensor resistance (passive type) across sensor leads with multimeter. Compare to vehicle spec. Replace sensor if open or out of spec.
- With wheel lifted and safe supports in place, spin the wheel and observe sensor signal using an oscilloscope or multimeter AC mode: passive should produce AC waveform; active should produce switching waveform. Look for missing pulses, low amplitude or noise.
- Perform continuity and short-to-power/ground checks on the wiring from the sensor connector to the ABS module connector. Repair any open or shorted wiring.
- Wiggle test the wiring and connectors while monitoring live data or scope to reproduce intermittent faults. Repair chafed/broken wires and secure harness.
- If wiring and sensor check good, inspect tone ring closely; replace or repair if teeth are damaged or air gap excessive. Correct air gap to spec.
- If sensor, wiring, and tone ring are good, consider module fault: verify other wheel sensors operate normally and, if suspect, test/replace ABS module per service manual.
- After repairs, clear codes and perform a road test while monitoring left front wheel speed data to confirm proper operation and that code does not return.
Likely causes
- Connector corrosion or loose connector at left front sensor
- Open or shorted wiring between sensor and ABS module
- Failed left front wheel speed sensor
- Tone ring damage or excessive air gap
Fault status
Status
Left front wheel speed sensor circuit fault detected — signal out of range, missing, open or shorted. This may disable ABS/traction control for the affected wheel until corrected.
Repair difficulty: Medium
Diagnostic time: 0.5-2 hours
Similar codes
Repair manuals
Manual library for HUMMER
138
Browse 138 HUMMER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.
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Code
C0237
OPEL
C — Chassis
Accelerator Pedal Position Sensor Incorrect Signal
AI status
Completed
Completed
100%
Causes
- Damaged or disconnected wheel speed sensor wiring or connector
- Corroded or contaminated sensor connector pins
- Damaged or faulty wheel speed sensor (Hall or passive tone sensor)
- Physical damage or misalignment of the tone ring/reluctor (missing teeth, heavy rust, debris)
- Short to power or ground in sensor circuit
- Faulty ABS/traction control module or poor module ground
Symptoms
- ABS warning lamp illuminated
- Traction control or stability control warning active
- Possible loss of ABS/traction control functionality
- Speedometer may show erratic behavior on some vehicles
- Possible intermittent behavior related to steering or wheel movement
What to check
- Read ABS and body control module codes and freeze frame data with scan tool
- Visual inspection of left front sensor, wiring harness, and connector for damage, corrosion, and contamination
- Check wheel bearing and hub area for loose components or excessive play
- Inspect tone ring/reluctor for missing teeth, cracks, heavy rust, or debris
- Wiggle test wiring while monitoring live wheel speed data for intermittent changes
- Measure resistance and/or output signal of sensor with multimeter or oscilloscope
Signal parameters
- Passive (magneto) sensor: AC voltage increases with speed; low speed generates small mV, higher speeds up to ~1–2 VAC depending on vehicle
- Active (Hall/electronic) sensor: digital square-wave output; typically 0–5V or 0–12V switching between reference and ground
- Expected resistance (passive type) commonly ~800–2000 Ω (vehicle-specific — consult manual)
- Reference/supply for active sensors typically 5V (some systems use 12V); verify with vehicle data
- Signal frequency: increases with wheel speed; expect a clean, consistent waveform on oscilloscope (roughly 10s–1000s Hz depending on speed)
- Duty cycle often near 50% for active sensors; look for missing pulses or irregular amplitude
Diagnostic algorithm
- Connect a scan tool. Read and record trouble codes, pending codes, freeze frame data and live left front wheel speed sensor values.
- Perform visual inspection of left front wheel area: sensor, tone ring, hub/bearing and wiring harness. Address obvious damage or debris first.
- With ignition ON (engine off), disconnect sensor connector and inspect pins for corrosion, bent pins, or water intrusion. Clean and reconnect or replace connector as needed.
- Check reference voltage and ground at the sensor connector for active sensors: backprobe connector with key ON. Verify supply voltage (typically ~5V) and good ground.
- Measure sensor resistance (passive type) across sensor leads with multimeter. Compare to vehicle spec. Replace sensor if open or out of spec.
- With wheel lifted and safe supports in place, spin the wheel and observe sensor signal using an oscilloscope or multimeter AC mode: passive should produce AC waveform; active should produce switching waveform. Look for missing pulses, low amplitude or noise.
- Perform continuity and short-to-power/ground checks on the wiring from the sensor connector to the ABS module connector. Repair any open or shorted wiring.
- Wiggle test the wiring and connectors while monitoring live data or scope to reproduce intermittent faults. Repair chafed/broken wires and secure harness.
- If wiring and sensor check good, inspect tone ring closely; replace or repair if teeth are damaged or air gap excessive. Correct air gap to spec.
- If sensor, wiring, and tone ring are good, consider module fault: verify other wheel sensors operate normally and, if suspect, test/replace ABS module per service manual.
- After repairs, clear codes and perform a road test while monitoring left front wheel speed data to confirm proper operation and that code does not return.
Likely causes
- Connector corrosion or loose connector at left front sensor
- Open or shorted wiring between sensor and ABS module
- Failed left front wheel speed sensor
- Tone ring damage or excessive air gap
Fault status
Status
Left front wheel speed sensor circuit fault detected — signal out of range, missing, open or shorted. This may disable ABS/traction control for the affected wheel until corrected.
Repair difficulty: Medium
Diagnostic time: 0.5-2 hours
Similar codes
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