ABS and brakes

C0070 — Rear Wheel Speed Sensor Signal Correlation Fault

Severity: medium Drive with care, to a shop

What C0070 means

The ABS control module constantly compares the rear wheel speed sensor signals with each other and with the front wheels. C0070 is stored when those signals disagree more than they should or do not make sense together. Because the module cannot trust wheel speed data, it usually disables ABS and stability control.

Symptoms

  • ABS warning light is on
  • Stability control or traction control light is on
  • ABS and ESC work in a reduced way or not at all
  • Traction control activates on a straight, dry road
  • False stability control intervention
  • Wheels may lock up under hard braking

Possible causes

  1. Failed or dirty rear wheel speed sensor on one side
  2. Damaged wiring harness or poor connector contact at the sensor
  3. Damaged or dirty tone ring (reluctor) on one side
  4. Worn rear wheel bearing with excess play
  5. Mismatched tire sizes or very uneven wear on the rear axle
  6. ABS module fault or a communication error between modules

How to diagnose

  1. Scan all ABS module codes and freeze frame data, and note any other wheel speed sensor codes
  2. Inspect the tires: same size, pressure and wear across the rear axle
  3. Compare live wheel speed data for all four wheels on a test drive to find the odd one out
  4. Inspect the rear sensors and wiring for breaks, chafing, corrosion and loose connectors
  5. Check the sensor air gap and clean metal debris off the sensor tip
  6. Inspect the tone ring for cracks, missing teeth and rust
  7. Check the rear wheel bearing for play
  8. Test the sensor resistance or signal and check the wiring to the module, including ground

Common fixes

  • Replace the faulty rear wheel speed sensor
  • Repair the wiring harness or replace a damaged connector
  • Replace the tone ring or the wheel bearing hub assembly
  • Fit matching tires with even wear on the rear axle
  • Update software or repair the ABS module if sensors and wiring test good

Questions and answers

What does code C0070 mean?

It is a rear wheel speed sensor correlation fault. The ABS module sees signals that do not agree and cannot rely on them. The exact wording can vary slightly by manufacturer.

Can I drive with C0070 set?

Yes, but carefully and not for long. Normal brakes usually work, but ABS and stability control may be disabled, which is risky on wet or slippery roads.

Can mismatched tires cause C0070?

Yes. Different tire sizes or heavily uneven wear on the rear axle make the wheels turn at different speeds, and the module may read that as a sensor problem.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.