Code
C0376
HUMMER
C — Chassis
Front/Rear Shaft Speed Mismatch
Views:
UK: 9
EN: 12
RU: 7
AI status
Completed
Completed
100%
Causes
- Faulty front or rear shaft speed sensor (wheel speed, transfer case output, or driveshaft speed sensor)
- Damaged wiring or poor connector connection between sensor and control module
- Missing or damaged reluctor/trigger ring or tone wheel
- Incorrect sensor air gap or misalignment
- Faulty ABS/traction/stability control module or transfer case control module
- Mechanical issue in driveline (slipping transfer case, differential, or damaged gear teeth)
Symptoms
- ABS, traction, or stability warning lamp(s) illuminated
- Traction/stability control disabled or intermittent operation
- Vehicle speedometer or cruise control may operate erratically (if tied to affected sensor)
- Unusual driveline noise or vibration if mechanical damage present
- Fault present only at certain speeds or during certain drive conditions
What to check
- Read freeze frame and live data with a scan tool; note front and rear shaft speed values and conditions when code set
- Clear codes and attempt to re-create the fault on road using a scan tool to compare front vs rear shaft speed traces
- Visually inspect speed sensors, reluctor rings/tone wheels, and wiring harnesses at front and rear axles and transfer case
- Check connectors for corrosion, bent pins, moisture intrusion, or loose fits
- Check for service bulletins or calibration updates for ABS/TCM/transfer case modules
Signal parameters
- Type: pulse/AC signal (passive sensor) or digital square wave (active sensor) depending on vehicle design
- Voltage: passive sensors produce AC voltage proportional to wheel speed; active sensors produce 0–12V (or 0–5V) square pulses
- Frequency: pulses per second increases smoothly with vehicle speed; should be zero at rest
- Expected behavior: front and rear speed signals should track each other proportionally for vehicles with linked drivetrain; no dropouts, steady amplitude/frequency ramps with acceleration
Diagnostic algorithm
- Connect a capable scan tool and record live data: compare front and rear shaft speed values across speeds and during acceleration/deceleration.
- Clear the code and perform a monitored test drive to confirm reoccurrence and note conditions (speed range, turning, gear, transfer case mode).
- Visually inspect both speed sensors and tone wheels/reluctor rings for damage, debris, ringing tooth missing, or excessive air gap; correct as necessary.
- Inspect wiring and connectors at each sensor: wiggle test while watching live data for dropouts; repair any damaged wires or corroded connectors.
- Measure sensor outputs with a multimeter/oscilloscope: passive sensors should show AC voltage at speed; active sensors should show a square wave (check reference voltage and ground).
- Verify sensor resistance vs specification (manufacturer values) and check reference power/ground at sensor connector.
- If sensor output looks suspect on one side, swap sensors (if identical) to see if the code follows the sensor; this helps isolate sensor vs module/wiring.
- Check transfer case/differential health if electrical checks pass: inspect for mechanical slip, damaged gears, or internal sensor mounting issues.
- Inspect and test ABS/TCM/transfer case module grounds and power feeds; inspect module connectors for corrosion or water intrusion.
- After repair or replacement, clear codes and perform a calibrated road test to confirm front and rear shaft speeds track and code does not return. Consult wiring diagrams and service manual torque/air-gap specs for final adjustments.
Likely causes
- Worn or contaminated speed sensor or reluctor ring
- Broken or corroded wiring/poor connector at one speed sensor
- Reluctor ring missing/damaged on front or rear output
- Transfer case output speed sensor fault or internal transfer case slip
Fault status
Status
C0376 — Front/Rear Shaft Speed Mismatch. Control module detected a significant difference between front and rear shaft speed sensor signals.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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