C1835

What Does Code C1835 Mean?

DTC C1835 indicates a detected fault within a specific current sense circuit. As a ‘C’ (Chassis) code, it typically points to an issue with a subsystem beyond the primary powertrain, often involving active chassis components such as the Anti-lock Braking System (ABS), Traction Control System (TCS), Electronic Stability Control (ESC), or potentially an Electronic Power Steering (EPS) system or other auxiliary motor-driven components. The diagnostic module responsible for monitoring this circuit (e.g., ABS Control Module, EPS Control Module, or an integrated Body Control Module/Chassis Control Module) has detected an implausible or incorrect current flow reading through a designated monitoring circuit. This circuit is designed to provide feedback on the current drawn by a specific component, often an electric motor or solenoid, to ensure its proper operation and to detect faults like opens, shorts, or excessive current draw. The module compares the sensed current value against predefined operational parameters and calibration limits. If the actual current deviates significantly from the expected range—either too high (indicating a short circuit or seized component) or too low (indicating an open circuit, high resistance, or component failure)—the module will set code C1835 and illuminate the corresponding warning light(s).

Common Symptoms

• ABS Warning Light: The Anti-lock Braking System indicator will likely illuminate on the instrument cluster.
• Traction Control/Stability Control Warning Light: The TCS or ESC warning light may also be illuminated, indicating these systems are compromised.
• Reduced Braking Performance: While basic hydraulic braking may remain, the advanced ABS/TCS functionalities will be disabled, potentially leading to increased stopping distances or loss of control during emergency braking on slippery surfaces.
• Stiff Brake Pedal: In systems where the current sense circuit relates to a brake booster pump motor, the pedal may become firm and difficult to depress, especially after multiple applications.
• No Apparent Symptoms (Intermittent Fault): In some cases, especially with intermittent electrical issues, the only symptom might be the illumination of a warning light without any noticeable change in vehicle operation, or the code may be stored in history without an active light.

What Causes the Code C1835?

• Faulty Component: The component whose current draw is being monitored (e.g., ABS pump motor, brake booster motor, EPS motor) may be faulty. This could include a seized motor, internal short, or open winding, causing incorrect current draw.
• Wiring Harness Issues: An open circuit, short to ground, short to power, or excessive resistance within the power, ground, or signal wires connecting the monitored component to its control module. This is a very common cause of current sense circuit failures.
• Corroded or Loose Electrical Connections: Poor contact at multi-pin connectors for the component or the control module can lead to intermittent or permanent high resistance, affecting current flow and sensor readings.
• Faulty Current Sense Resistor/Shunt: The current sense circuit often incorporates a precision resistor or shunt within the control module itself to measure current flow. If this component fails internally, it can lead to inaccurate readings.
• Defective Control Module: The primary control module (e.g., ABS Control Module) responsible for monitoring the current sense circuit may have an internal fault, such preventing it from correctly interpreting current signals or having an internal short/open in the driver circuit.
• System Voltage Issues: While less common as a direct cause, severely low or unstable system voltage can sometimes lead to erroneous current sense readings or prevent components from drawing their expected current.

How to Diagnose and Troubleshoot

Diagnosing C1835 requires a systematic approach using a digital multimeter (DMM) and a capable OBD-II scanner:

1. Retrieve All DTCs: Use an advanced OBD-II scanner capable of reading chassis codes. Note C1835 and any other related ‘C’, ‘B’, or ‘U’ codes, as they may provide clues to the root cause (e.g., communication issues or other component failures).
2. Visual Inspection:
   • Inspect the wiring harness associated with the suspected current-monitored component (e.g., ABS pump motor, EPS motor) for signs of damage, chafing, corrosion, or modifications. Pay close attention to areas where the harness passes through firewalls, over sharp edges, or near moving parts.
   • Check the electrical connectors at the component and the control module for corrosion, bent pins, or signs of overheating. Ensure they are securely seated.
3. Verify System Voltage:
   • Using a DMM, check battery voltage. Ensure it is stable, typically between 12.0V and 12.6V with the engine off, and 13.5V to 14.5V with the engine running. Low voltage can sometimes cause electrical anomalies.
   • Check for stable voltage supply at the control module’s power input and at the power supply terminal of the suspected component.
4. Test the Monitored Component:
   • Identify the component monitored by the C1835 circuit (consult service information for the specific vehicle).
   • If possible and safe, disconnect the component and check its internal resistance using a DMM. Compare readings to manufacturer specifications. An open circuit (infinite resistance) or a short circuit (near zero resistance) indicates an internal fault.
   • If the component is an electric motor, check for smooth, free rotation (if accessible) and ensure no mechanical binding.
5. Inspect the Current Sense Circuit Wiring:
   • With the ignition off and relevant connectors disconnected (both at the control module and the component), use a DMM to perform continuity checks on the individual wires in the current sense circuit. Check for continuity between the control module connector and the component connector for each wire (power, ground, and any dedicated sense lines).
   • Check for shorts to ground: With one DMM lead on each wire terminal (disconnected at both ends), place the other DMM lead to a known good chassis ground. There should be infinite resistance.
   • Check for shorts to power: With one DMM lead on each wire terminal, place the other DMM lead to a known good 12V power source. There should be infinite resistance.
   • Check for high resistance within the wires by measuring resistance end-to-end. Any reading above a few ohms indicates an issue.
6. Utilize Bi-directional Control (if available):
   • Some advanced scanners offer bi-directional control, allowing you to command the suspect component (e.g., ABS pump motor) to activate. While activated, monitor live data streams for the current sense circuit. Compare actual current draw to specified values.
   • If no current is drawn when commanded, or the current is excessively high/low, it further points to an issue with the component or its direct power/ground supply.
7. Test the Control Module:
   • If all wiring, connections, and the component itself test within specifications, the fault likely lies within the control module. This could be an internal failure of the current sense circuitry or the driver transistors.
   • Module replacement should only be considered after thorough verification of all external components and wiring, as module replacement is often expensive and may require programming/coding.

Recommended Repairs and Solutions

The resolution for C1835 depends entirely on the root cause identified during diagnosis:

• Repair or Replace Wiring/Connectors: If the diagnostic steps reveal an open circuit, short, or high resistance in the wiring harness or connectors, repair the damaged section of the harness using proper automotive wiring repair techniques (e.g., soldering and heat-shrinking) or replace the faulty connector. Ensure secure and corrosion-free connections.
• Replace the Faulty Component: If the component being monitored (e.g., ABS pump motor, EPS motor) tests as internally faulty (e.g., seized, open windings, shorted), it must be replaced. For ABS pump motors, this often means replacing the entire ABS hydraulic unit and control module assembly, or sometimes just the motor itself depending on the design.
• Replace the Control Module: If comprehensive testing of the component and all related wiring confirms their integrity, and the fault is isolated to the control module’s internal current sense circuitry or driver, then the control module (e.g., ABS Control Module) will require replacement. Be aware that many modern control modules require specific programming or coding to the vehicle’s VIN and options after installation. Always follow manufacturer-specific procedures for module replacement and calibration.
• Address Power Supply Issues: If diagnostic steps indicate issues with the vehicle’s electrical power supply, repair or replace the affected component (e.g., battery, alternator, main power fuses, or ground connections).
• Clear DTCs and Retest: After any repair, clear all stored diagnostic trouble codes using an OBD-II scanner. Then, perform a test drive or activate the affected system to verify the repair and ensure the C1835 code does not return.