C1407

What Does Code C1407 Mean?

DTC C1407 indicates a “Traction Control Valve Rear Circuit Short To Battery.” This diagnostic trouble code is specific to the Anti-lock Braking System (ABS) and Traction Control System (TCS) module, rather than the Engine Control Module (ECM) or Powertrain Control Module (PCM). The ABS/TCS control module monitors the electrical circuits for the various hydraulic solenoids within the ABS modulator assembly. The C1407 code is triggered when the ABS/TCS module detects an abnormally high voltage, specifically a voltage level approaching or equal to battery voltage, on the control circuit for the rear traction control valve solenoid, when this solenoid is commanded off or when its circuit should exhibit a different voltage characteristic based on system operation. This typically signifies an unintended direct connection between the solenoid’s control wire and a constant power source, or a fault within the solenoid itself causing an internal short to power.

Common Symptoms

• Traction Control Light Illuminated: The primary indicator, signaling a fault within the TCS.
• ABS Warning Light Illuminated: Since the TCS shares components and functions with the ABS, an ABS warning light may also illuminate.
• Reduced Traction Control Effectiveness: The system may be disabled, leading to wheelspin during acceleration on slippery surfaces.
• No ABS Operation: In some cases, a severe fault in the hydraulic unit can disable the entire ABS functionality.
• Abnormal Brake Pedal Feel: While less common for this specific code, severe internal modulator issues can sometimes affect pedal feel.

What Causes the Code C1407?

• Damaged Wiring Harness: A short circuit to battery voltage in the wiring leading to the rear traction control valve solenoid. This can be caused by chafing, pinching, or corrosion allowing contact with a constant power wire.
• Faulty Rear Traction Control Valve Solenoid: An internal short within the solenoid itself, causing its control circuit to draw excessive current or exhibit a constant high voltage when not commanded.
• Corrosion in Electrical Connectors: Moisture and corrosion can create an unintended electrical path, bridging the solenoid’s control circuit to a power supply within the connector.
• Failed ABS/TCS Control Module: While less common, an internal fault within the ABS/TCS module could cause it to incorrectly interpret circuit voltage or, in rare cases, supply inappropriate voltage to the solenoid circuit.

How to Diagnose and Troubleshoot

Diagnosing C1407 requires a methodical approach, focusing on circuit integrity and component functionality:

1. Retrieve and Record DTCs: Connect an OBD-II scanner capable of communicating with the ABS/TCS module. Note all present and pending C-codes. Observe live data for the ABS/TCS system if available, paying attention to solenoid states and circuit voltages.
2. Visual Inspection:
   • Inspect the wiring harness leading to the ABS hydraulic unit for visible signs of damage, chafing, pinching, or melting.
   • Examine the electrical connectors at the ABS hydraulic unit and the ABS/TCS control module for corrosion, bent pins, or loose connections.
   • Pay particular attention to areas where the harness passes through firewalls, over sharp edges, or near exhaust components.
3. Perform a Circuit Voltage Test (Ignition On, Engine Off):
   • Locate the specific wire for the rear traction control valve solenoid at the ABS hydraulic unit connector. Refer to the vehicle’s specific wiring diagram for pinout identification.
   • With the connector disconnected from the ABS hydraulic unit, use a digital multimeter (DMM) to measure voltage between the solenoid’s control wire terminal (on the harness side) and a known good ground.
   • A reading close to battery voltage (e.g., 12V) indicates a short to battery in the harness. If the voltage is 0V or close to it, the short might be internal to the solenoid or an intermittent wiring fault.
4. Perform a Continuity and Resistance Test:
   • With the battery disconnected and the ABS hydraulic unit connector unplugged, measure the resistance of the rear traction control valve solenoid itself (between its two terminals, or between its terminal and vehicle ground, depending on the solenoid’s design, using the wiring diagram). Compare this reading to manufacturer specifications. An open circuit or extremely low resistance indicates a faulty solenoid.
   • Test for continuity between the solenoid’s control wire terminal (harness side) and battery positive (+) with the battery disconnected. This will confirm a direct short to battery in the wiring.
5. ABS/TCS Module Output Test (Advanced):
   • If available, use a bi-directional scan tool to command the rear traction control valve solenoid on and off while monitoring the circuit voltage at the module and at the solenoid connector. This can help isolate whether the module is erroneously supplying voltage or if the short exists externally.

Recommended Repairs and Solutions

• Repair or Replace Damaged Wiring: If the diagnosis confirms a short to battery within the wiring harness, the damaged section of the wire must be repaired or the entire sub-harness replaced. Ensure proper insulation and routing to prevent future damage.
• Replace Faulty ABS Hydraulic Unit (Solenoid): If the rear traction control valve solenoid is found to be internally shorted, it typically necessitates the replacement of the entire ABS hydraulic modulator assembly, as individual solenoids are often not serviceable separately. Some specialized repair facilities might be able to rebuild these units, but complete replacement is the most common solution.
• Clean or Repair Corroded Connectors: If corrosion is present in the connectors, carefully clean the terminals using electrical contact cleaner and a small brush. If pins are severely corroded or damaged, the connector housing or individual terminals may need to be replaced. Ensure a tight, weather-sealed connection after reassembly.
• Replace ABS/TCS Control Module: Only consider replacing the ABS/TCS control module after thoroughly ruling out all wiring and solenoid issues. Module replacement often requires programming or calibration specific to the vehicle, which must be performed by a qualified technician with appropriate diagnostic tools.
• Post-Repair Procedures: After any repair involving the ABS hydraulic unit, it is crucial to perform a proper brake fluid bleed, including a scan tool-assisted ABS bleed if specified by the manufacturer, to purge air from the system. Clear the DTCs and perform a test drive to confirm the repair and ensure the code does not return.