C1707

What Does Code C1707 Mean?

Diagnostic Trouble Code (DTC) C1707 signifies a “Left Rear Center Sensor Circuit Fault” within the vehicle’s Chassis (C-code) control system. This code typically indicates an electrical malfunction in the circuit of a sensor located at the left rear wheel assembly, which is monitored by a control module, most commonly the Anti-lock Braking System (ABS) module, Traction Control System (TCS) module, or Electronic Stability Control (ESC) module. The term “Center” often refers to a wheel speed sensor integrated within the wheel hub or axle assembly, or potentially another critical chassis sensor (e.g., for active suspension or yaw rate) positioned in that vicinity.

The control module detects this fault when it identifies an electrical anomaly within the sensor’s circuit. This could manifest as an open circuit (no signal), a short circuit to ground, a short circuit to voltage, or an out-of-range resistance value that deviates significantly from expected operational parameters. When the circuit integrity is compromised, the module is unable to receive reliable data from the sensor, leading to the illumination of associated warning lights and the setting of this DTC.

Common Symptoms

• ABS Warning Light: The Anti-lock Braking System warning lamp will illuminate on the instrument cluster.
• Traction Control System (TCS) Warning Light: The traction control warning lamp will often illuminate, and the system may be disabled.
• Electronic Stability Control (ESC/VSC) Warning Light: The stability control warning lamp will typically illuminate, and the system may be disabled.
• Impaired ABS/TCS/ESC Function: These safety systems may be partially or completely inoperative, potentially affecting braking performance and vehicle stability during evasive maneuvers or on low-traction surfaces.
• Unusual Braking Behavior: In some cases, the vehicle might exhibit a harder brake pedal or inconsistent braking feel due to the disablement of ABS.
• Cruise Control Inoperability: Many vehicles disable cruise control when ABS/TCS/ESC faults are present.
• Erratic Speedometer/Odometer Readings: While less common for a single rear wheel sensor fault, an intermittent signal could potentially affect speed readings if that specific sensor contributes to the vehicle speed calculation.

What Causes the Code C1707?

• Faulty Left Rear Wheel Speed Sensor: The sensor itself may have an internal electrical fault, such as an open circuit, short circuit, or degraded sensing element, preventing it from generating a proper signal.
• Damaged Wiring Harness: The electrical wiring connecting the left rear sensor to its control module can become chafed, cut, corroded, or stretched due to road debris, environmental exposure (water, salt), or contact with moving suspension components. This leads to an open or short circuit.
• Corroded or Loose Electrical Connector: The multi-pin connector at the sensor or at the control module can suffer from corrosion, dirt ingress, or become dislodged, resulting in high resistance or an intermittent connection within the circuit.
• Damaged Tone Ring/Reluctor Wheel: While a “circuit fault” primarily implies electrical integrity, severe damage to the magnetic or toothed tone ring (on the axle or hub) that the sensor reads can cause the sensor to produce such an erratic or absent signal that the control module interprets it as a circuit malfunction.
• Faulty ABS/TCS/ESC Control Module: Although less common, the internal circuitry of the chassis control module responsible for processing the signal from the left rear sensor may be damaged, leading to misinterpretation of the sensor’s circuit status.

How to Diagnose and Troubleshoot

Diagnosis of C1707 requires a systematic approach using specialized tools:

1. Visual Inspection: Begin by visually inspecting the left rear wheel speed sensor, its entire wiring harness routing from the sensor to the chassis, and all associated electrical connectors. Look for signs of physical damage, chafing, cuts, corrosion, bent pins, or loose connections. Pay close attention to areas where the harness passes through grommets or near moving parts. Inspect the wheel bearing and tone ring for visible damage, missing teeth, or excessive debris.
2. OBD-II Scan Tool Live Data: Connect an advanced diagnostic scan tool capable of communicating with the ABS/TCS/ESC module. Navigate to the live data stream and monitor the wheel speed sensor readings for all four wheels. While rotating the left rear wheel by hand (if possible) or driving the vehicle slowly, compare the left rear sensor’s output (typically in MPH or km/h) to the other wheels. A faulty circuit will likely show 0 MPH, an erratic reading, or a vastly different reading compared to the other wheels at the same speed.
3. Digital Multimeter (DMM) Tests:
   • Sensor Resistance Check (Passive Sensors): Disconnect the sensor’s electrical connector. Using a DMM, measure the resistance across the two sensor terminals. Compare the reading to manufacturer specifications (typically several hundred to a few thousand ohms). An “OL” (open loop) indicates an open circuit, while a reading close to 0 ohms suggests an internal short circuit. Note: Active (hall effect) sensors often do not have a simple resistance value and require different testing methods.
   • Sensor Voltage Output Check (Passive Sensors): With the sensor connected and the vehicle safely raised and secured, rotate the left rear wheel by hand. Using a DMM set to AC voltage, probe the sensor’s output wires (back-probe if necessary). A passive sensor should generate a low AC voltage signal (e.g., 0.1V to 1V) that increases in frequency and amplitude with wheel speed.
   • Voltage Supply Check (Active Sensors): Disconnect the sensor connector. With the ignition ON, use a DMM to check for reference voltage (typically 5V or 12V) and a clean ground signal at the vehicle-side harness connector terminals that supply power to the sensor. This confirms the control module is providing power.
   • Wiring Harness Continuity and Short Checks: Disconnect both ends of the wiring harness (at the sensor and at the control module). Use a DMM to perform continuity checks on each wire in the harness from end-to-end. Resistance should be very low (close to 0 ohms). Then, check each wire for shorts to ground and shorts to power.
4. Wiggle Test: With the scan tool monitoring live data, gently wiggle and manipulate the wiring harness and connectors around the left rear sensor, suspension components, and control module. Observe if the sensor reading or the DTC status changes, indicating an intermittent connection.

Recommended Repairs and Solutions

Based on the diagnostic findings, the following repairs are typically recommended:

• Replace the Left Rear Wheel Speed Sensor: If the sensor itself tests faulty (incorrect resistance, no voltage output, or erratic live data), replacement is the most common solution. Ensure the replacement sensor is a direct OEM-equivalent fit for your specific vehicle make and model, as incorrect sensors can cause further issues.
• Repair or Replace Damaged Wiring Harness: If the wiring harness is found to be cut, chafed, or corroded, perform a professional repair. Use appropriate automotive-grade wire, solder connections, and seal with heat-shrink tubing. For extensive damage, replacing the entire harness section is recommended. Ensure proper strain relief and routing to prevent future damage.
• Clean and Secure Electrical Connectors: If corrosion or poor contact is identified at the connectors, carefully clean the terminals using electrical contact cleaner and a small brush. Apply a small amount of dielectric grease to prevent future corrosion and ensure a secure connection. Reconnect firmly.
• Replace Damaged Tone Ring/Reluctor Wheel: If the tone ring is cracked, missing teeth, or excessively corroded, it must be replaced. This often involves significant disassembly of the wheel hub or axle assembly.
• Replace ABS/TCS/ESC Control Module: Only consider replacing the control module as a last resort, after thoroughly verifying that the sensor, wiring harness, and tone ring are all in perfect working order. Module replacement often requires specialized programming and calibration with a factory-level scan tool.
• Clear DTCs and Road Test: After completing any repairs, use an OBD-II scan tool to clear the C1707 DTC and any associated codes. Perform a comprehensive road test to confirm that the issue is resolved and the warning lights remain off. Ensure proper ABS/TCS/ESC functionality if conditions permit.