OBD-II trouble code
C0300: Rear Propshaft Speed Sensor Circuit
The control module detected a fault in the rear propshaft (driveshaft) speed sensor circuit. On four-wheel-drive and all-wheel-drive vehicles this sensor feeds the transfer case and stability systems, so a fault commonly turns off automatic 4WD/AWD and lights the ABS and Service 4WD warnings.
Quick facts
- System
- Chassis
- Category
- ABS / Wheel Speed
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $90 – $400
- DIY difficulty
- Intermediate DIY
What does C0300 mean?
C0300 sets when a control module — usually the Transfer Case Control Module (TCCM), or on some vehicles the powertrain/ABS module — detects a problem with the rear propshaft speed sensor circuit. This sensor is a small magnetic pickup that watches a toothed ring on the rear driveshaft (propeller shaft), the shaft that carries power from the transmission or transfer case back to the rear differential. As the shaft turns, the sensor produces a pulsing signal whose frequency tells the module how fast the rear wheels are actually being driven.
On four-wheel-drive and all-wheel-drive vehicles that number is important. The transfer case compares rear driveshaft speed against front driveshaft (or wheel) speed to detect slip and decide how much torque to send to the front axle in automatic 4WD/AWD modes. Anti-lock braking, traction control, and stability control can also use the signal. When the module sees the circuit open, shorted, or reading an implausible value, it can no longer trust the data, so it disables the affected functions and turns on warning lights.
Different manufacturers use slightly different names for the same code — Rear Propeller Shaft Speed Sensor Circuit, Rear Driveshaft Speed Sensor, or simply Rear Wheel Speed Sensor on some applications — but the idea is the same. Because C-code definitions and pin assignments vary by make, confirm your specific vehicle's meaning before condemning parts.
A large share of C0300 faults are wiring and connector problems rather than a bad sensor. The sensor lives under the vehicle in a harsh environment, so corroded terminals, chafed wires, road-salt damage, and a debris- or rust-covered tone ring are all common. Inspect the wiring and the sensor tip before replacing the sensor itself.
Common causes
- Faulty rear propshaft (driveshaft) speed sensor
- Damaged, corroded, or loose sensor wiring and connector
- Debris, rust, or damage on the tone ring / reluctor the sensor reads
- Excessive air gap between the sensor tip and the tone ring
- Open or short in the circuit between the sensor and the control module
- Poor ground or low system voltage affecting the signal
Symptoms
- ABS and traction control warning lights on
- Service 4WD message; automatic 4WD/AWD may be disabled
- Erratic or dropped speedometer/odometer reading in some cases
- Cruise control disabled or cutting out
- Occasional erratic ABS or brake-pedal pulsing
Diagnostic steps
- 1.Scan for codes and note whether the front propshaft sensor (C0305) or wheel-speed codes are present too — several together point at a shared wiring or ground problem.
- 2.Locate the rear propshaft speed sensor and inspect its connector and wiring for corrosion, chafing, and road-salt damage.
- 3.Remove the sensor and check the tip and the tone ring for metal debris, rust, or damaged teeth; verify the air gap is correct.
- 4.Back-probe the circuit and compare the sensor's live signal to a known-good wheel/propshaft speed while driving or spinning the shaft.
- 5.Check for continuity, shorts to ground/power, and a clean ground on the sensor circuit back to the module.
- 6.If wiring and tone ring are good but the signal is missing or erratic, replace the sensor and clear the code.
Repair cost
$90 – $400
A rear propshaft speed sensor is often a modestly priced part; replacement typically runs $90-$300 including labor depending on access. Wiring or connector repair can be less if the sensor is fine. If the fault is actually inside the transfer case (tone ring/reluctor) the cost can be higher.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with wheel speed sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.