C1708

What Does Code C1708 Mean?

DTC C1708 indicates a specific electrical fault within the circuit of the right rear center sensor, specifically a “Short to Vbat” (Battery Voltage). This diagnostic trouble code is typically assigned to a chassis control module, such as the Electronic Brake Control Module (EBCM), Anti-lock Brake System (ABS) module, Traction Control System (TCS) module, or a suspension control module, depending on the vehicle’s specific configuration and the function of the “center sensor.” The term “center sensor” in the right rear context most commonly refers to a wheel speed sensor integrated into the wheel hub or a dedicated ride height sensor for active suspension systems.

The control module responsible for monitoring this circuit detects an abnormally high voltage level on the sensor’s signal wire, indicating that the circuit is receiving voltage at or near the vehicle’s battery potential (typically 12-14.5V) when it should be at a much lower reference voltage, fluctuating signal voltage, or ground. This condition suggests an unintended electrical path, preventing the module from receiving accurate or any data from the sensor. Consequently, the module interprets this as a critical circuit malfunction, rendering the associated system (e.g., ABS, TCS, stability control, or active suspension) inoperative or significantly impaired.

Common Symptoms

• Illumination of the ABS Warning Light on the instrument cluster.
• Activation of the Traction Control System (TCS) Warning Light.
• Reduced or complete loss of ABS, TCS, and/or Electronic Stability Control (ESC) functionality.
• Inconsistent or erroneous speedometer readings (less common for a dedicated “center” sensor, but possible if it’s a primary wheel speed input).
• Issues with vehicle handling or ride quality if related to an active suspension ride height sensor.
• Brake pedal pulsation or unusual noise during braking, especially during light braking or at low speeds.
• Potential activation of the Brake System Warning Light.

What Causes the Code C1708?

• Damaged Wiring Harness: The most frequent cause is chafed, cut, or otherwise compromised wiring in the right rear sensor circuit, leading to the sensor’s signal wire (or a related low-voltage wire) making direct contact with a fused 12V power supply wire (Vbat) somewhere along its path from the sensor to the control module. This can be due to external damage, vibration, or poor routing.
• Faulty Right Rear Center Sensor: An internal short circuit within the sensor itself, causing its internal signal generation components to short directly to its internal power supply provided by the vehicle, effectively sending Vbat down the signal line. This is more common with active (powered) sensors.
• Corroded or Damaged Connector: Corrosion, bent pins, or foreign material within the multi-pin connector for the right rear sensor, or even at the control module connector, creating an unintended bridge between the sensor’s signal pin and a Vbat pin.
• Internal Control Module Malfunction: While less common, an internal fault within the EBCM, ABS module, or relevant suspension control module could potentially misinterpret a normal signal as a short to Vbat, or in rare cases, an internal short within the module could apply Vbat to the sensor circuit.

How to Diagnose and Troubleshoot

A systematic diagnostic approach is crucial for C1708. Begin with a comprehensive visual inspection and then proceed with electrical testing using a digital multimeter (DMM) and an advanced OBD-II scan tool.

1. Verify the Code and Freeze Frame Data: Connect an OBD-II scan tool and confirm the presence of C1708. Review any associated freeze frame data to understand the operating conditions (vehicle speed, engine RPM, load, etc.) at the time the code was set. Check for other related ABS/TCS or chassis codes.
2. Perform a Thorough Visual Inspection: Carefully inspect the entire wiring harness leading to the right rear sensor. Pay close attention to areas where the harness passes through grommets, near sharp edges, exhaust components, moving suspension parts, or areas prone to road debris impact. Look for signs of chafing, cuts, rodent damage, or loose connections. Inspect the sensor itself for physical damage and ensure its mounting is secure. Disconnect and inspect the sensor’s electrical connector for bent pins, corrosion, moisture, or debris. Extend this inspection to the control module connector if accessible.
3. Isolate the Sensor Circuit:
   • Disconnect the right rear sensor’s electrical connector.
   • With the ignition OFF, use a DMM to measure resistance between the signal pin (refer to wiring diagram for correct pin) at the harness-side sensor connector and chassis ground. There should be infinite resistance (open circuit). If low resistance or continuity to ground is found, there is a short to ground. (Though the code is Short to Vbat, checking for unintended shorts is good practice).
   • With the ignition ON, measure the voltage on the sensor’s signal wire pin at the harness connector (with the sensor still disconnected). Expect to see a low reference voltage (e.g., 0-5V) or zero voltage, depending on the sensor type. If Vbat (12V+) is present, the short is in the wiring harness between the connector and the control module, or within the control module itself.
4. Check for Short to Vbat in the Wiring Harness:
   • If Vbat was found on the signal wire with the sensor disconnected, further isolate by disconnecting the control module (EBCM/ABS module).
   • With both the sensor and control module connectors disconnected, measure the resistance between the signal wire pin and all other power supply pins (e.g., 12V constant, ignition switched 12V) at both ends of the harness. There should be infinite resistance. Any continuity indicates a short between these wires.
5. Test the Sensor Itself (if accessible for electrical testing):
   • While C1708 points to a circuit short, an internally shorted sensor can cause this. If the sensor is an inductive type, measure its internal resistance (refer to manufacturer specifications). An active Hall-effect type sensor would require power and ground supplied to it and an oscilloscope to check for signal output while simulated motion (e.g., spinning the wheel) is applied. However, for a “short to Vbat” issue, if the wiring tests clean and Vbat is present on the signal wire only when the sensor is connected, it strongly implicates the sensor.
6. Control Module Self-Test and Data Monitoring: If all wiring and sensor tests pass, and no external short is found, use a scan tool to monitor live data from other wheel speed sensors or similar sensors to compare their readings. If the control module allows, perform a self-test of the ABS/TCS system to check for further internal faults.

Recommended Repairs and Solutions

Once the source of the short to Vbat has been identified through the diagnostic steps, the appropriate repair can be executed:

• Repair or Replace Damaged Wiring: If the wiring harness is found to be shorted to Vbat, the damaged section must be repaired. For professional and durable repairs, use solder and heat-shrink tubing for individual wire repairs, or replace the entire damaged section of the harness. Ensure proper routing and securement to prevent future damage.
• Replace the Right Rear Center Sensor: If the sensor itself is determined to have an internal short causing the Vbat condition, it must be replaced. Always use an OEM-quality replacement part to ensure compatibility and proper system function.
• Clean or Repair Connector Terminals: If corrosion, bent pins, or loose terminals at the sensor or module connector are the cause, carefully clean the terminals with electrical contact cleaner and a suitable brush, or use a pick tool to straighten bent pins. If the damage is severe, replacing the connector housing and individual terminals may be necessary. Ensure a tight, secure connection upon reassembly.
• Replace the Control Module (Last Resort): Only if all other components (wiring, sensor, connectors) have been thoroughly tested and confirmed to be functioning correctly should the control module (e.g., EBCM/ABS module) be considered for replacement. Control module replacement often requires programming or calibration with a specialized scan tool.
• Clear DTCs and Test Drive: After performing the repair, clear all diagnostic trouble codes from the control module memory using an OBD-II scan tool. Then, conduct a comprehensive test drive to confirm that the C1708 code does not return and that the affected system (ABS, TCS, stability control, or suspension) is operating correctly.