Fix C0035: Mechanic’s Solutions That WORKED!

The C0035: Left Front Wheel Speed Sensor Circuit indicates issue within the left front wheel speed sensor circuit. This sensor plays a crucial role in your vehicle’s anti-lock braking system (ABS), helping to monitor the speed of the left front wheel to adjust braking pressure accordingly.

When this code pops up, it indicates an intermittent or faulty signal from the sensor, which can lead to problems like random ABS activation. Addressing this issue is vital for maintaining the safety and effectiveness of your vehicle’s braking system.

C0035 quick overview

MeaningC0035: Left Front Wheel Speed Sensor Circuit
Is it serious?Yes, it affects the ABS, a critical safety feature.
Possible causes– Faulty or intermittent wheel speed sensor
– Damaged wiring or connectors
– Issues with the hub assembly that includes the sensor
– Corrosion or damage within the wiring harness
How to diagnose?Check the wiring and connectors for damage or corrosion.
Monitor the wheel speed sensor’s output while driving to catch intermittent issues.
Inspect the hub assembly for play or damage if it includes the sensor.
Replace the wiring harness if damage is suspected within the insulation.
Consult a Technical Service Bulletin (TSB) for known issues related to this code.
Overview of C0035 trouble code

C0035 Meaning

Imagine driving and suddenly your car decides to pump the brakes on its own — that’s the kind of scenario the C0035 code can hint at. This code tells you there’s a glitch in the system that checks how fast the front left wheel is spinning.

It could be a simple wiring issue, something wrong with the sensor itself, or even a problem with the wheel’s bearing if the sensor is part of the hub. Fixing it might require checking the wires for hidden damage, replacing the sensor, or sometimes even getting a new hub assembly if that’s where the sensor lives.

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How to fix C0035 – learn from mechanics

I looked into C0035 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Chevrolet C0035

Vehicle information 2005 Chevrolet Equinox LT 3.4L

Issue + repair history

  • ABS pump randomly comes on for no reason.
  • Sets code C0035 (left front wheel speed sensor intermittent).
  • Checked wiring and connections for opens, found no problems.
  • Replaced hub assembly due to play in the hub, which includes a new sensor.
  • Symptom seemed fixed for two days but then returned with the same intermittent problem.
  • Code sets after several occurrences of engaging for no apparent reason.
  • Monitored sensors with Verdict while driving but did not observe any issues.

Other OBD2 Codes + Test Results

  • No additional codes mentioned.
  • No further test results provided.

Mechanic suggestions

  • Suggested checking for breaks in the wiring harness, particularly the harness between the wheel speed connector and the frame.
  • Advised stretching and wiggling the harness between the wheel and frame while measuring continuity to identify breaks.
  • Recommended replacing both circuits inside the wire loom between the wheel speed connector and the frame, particularly where it connects to the lower control arm, and soldering both ends.
  • Proposed replacing the wire harness that the sensor plugs into, as breaks in the harness can be challenging to find.
  • Mentioned the availability of a replacement plug with a harness from GM for the wiring harness to the speed sensor.
  • Pointed out the existence of a Technical Service Bulletin (TSB) on this issue and advised measuring voltage while turning the wheel.
  • Warned about aftermarket hub assemblies not reading correctly.
  • Suggested removing the RIGHT ABS sensor and cleaning the surface under the sensor, as rust may push the sensor away from the tone ring, causing ABS activity during non-ABS conditions.
  • Recommended closely inspecting the wiring harness running along the lower control arm, as broken wires may be hidden inside the insulation.
  • Advised replacing the harness on that wheel, as they are known to be broken inside the insulation, causing an open circuit.

Final fix

  • Removed the long harness from the vehicle, ohmed it while wiggling it up and down, and replaced it, which resolved the issue.

Case #2: Chevrolet C0035

Vehicle information 2007 Chevrolet Tahoe LS 4.8L

Issue + repair history

  • Vehicle sets code C0040 (RF Speed Sensor Circuit).
  • Occurred after the customer got new tires; Brake and ABS lights came on, and DIC displayed “Service Traction Control System.”
  • No 12V detected on the Grey/White wire, which should be present according to Alldata.
  • Tested sensor power wire to ground and signal return wire to ground separately; readings indicated open, not shorted to ground.
  • Oddity: LF sensor reads 1375 ohms on the power wire.
  • When applying 12V to the RF sensor and hooking up a Modis to the signal wire, a signal is obtained. Similar signal observed from the LF sensor.

Other OBD2 Codes + Test Results

  • No additional codes mentioned.
  • Test results included readings on power wire, signal return wire, and resistance tests.

Mechanic suggestions

  • Check the connector at the wheel speed sensor for broken wires inside the insulation.
  • Inspect the 12V wire from the connector to the EBCM for an open circuit, as tire replacement might have caused damage to the connector or wires.
  • Swap right and left sensors to see if the code follows, eliminating the sensor and wires as potential issues.
  • Consider the possibility of the sensor being damaged during tire rotation, as seen in similar cases.
  • Utilize GM’s Tech2 tool to determine if the sensor voltage has been disabled, providing clues about the circuit’s integrity.
  • Load circuits to examine them under real-world conditions, as resistance testing may not provide accurate results.
  • Consider external factors like snow chains or poorly fitted traction devices causing sensor damage, especially in snow-prone areas.

Final fix

  • Moving the sensor left to right indicated a sensor issue, and replacing it resolved the problem.

Case #3: Oldsmobile C0035

Vehicle information 2002 Oldsmobile Intrigue GX 3.5L

Issue + repair history

  • Car came in with ABS light on and Code C0035 (Left Front Wheel Speed Sensor Circuit).
  • Left front sensor inspected; found something in the axle. Replaced axle, wheel bearing, and ABS wiring harness.
  • After work was completed, got code C0040 (Right Front Wheel Speed Sensor Circuit).
  • If left sensor is unplugged, code C0040 disappears, but C0035 comes back.

Other OBD2 Codes + Test Results

  • No additional codes mentioned.
  • Test results indicate issues with the right front speed sensor despite inspection showing everything seems fine on the right.

Mechanic suggestions

  • Verify if OEM parts were used for replacements.
  • Check the harness attached to the lower control arm for any issues, as there have been many reported problems with this wiring. Consider using a dealer-offered pigtail for this.
  • Scan the vehicle to see what the speed sensors are picking up or not picking up. In more difficult cases, use a lab scope on the sensors and compare the waveforms. Bad sensors usually show up as a smaller pattern at the same speed.
  • Ensure all tires are the same, as differences in tire size or type can affect sensor readings.
  • Consider the brand of wheel bearing used, as using OEM parts might be preferable.

Final fix

  • After replacing the front left hub, the right front speed sensor kept checking bad. Replaced the right front hub, and the issue was resolved with no more codes.

How to diagnose C0035

I made you an overview of solving this DTC, based on all the advice that was suggested by certified mechanics to address this issue in previously mentioned service cases.

Diagnostic StepExplanation
Inspect wiring and connectorsLook for visible signs of wear, corrosion, or damage that could interrupt the sensor’s signal.
Monitor sensor output while drivingUse diagnostic tools to observe the sensor’s performance in real conditions, looking for drops or spikes in signal.
Check the hub assemblySince the sensor might be integrated, inspect for any mechanical issues that could affect its performance.
Replace the wiring harnessIf there are suspected breaks inside the insulation, a complete harness replacement might be necessary.
Consult TSBs for known issuesManufacturers may have identified and provided solutions for common issues related to this code.
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