OBD-II Diagnostic Trouble Code
C0070 — Front Wheel Speed Sensor Asymmetric Output
C0070 indicates the two front wheel speed sensors are producing mismatched outputs. The ABS module saw a speed difference between the left and right front wheels larger than it allows during straight-line driving. Unequal tire size or one weak sensor signal is the usual cause.
Severity 3/5
Truck-relevant
Service this week
Severity
Service this week
Front Wheel Speed Sensor Asymmetric Output
Code
C0070
Category
Chassis
Subsystem
Brakes
Truck-relevant
Yes
What this means for truckers
C0070 (Front Wheel Speed Sensor Asymmetric Output) — the two front sensors disagree under conditions where they shouldn't (straight-line driving). Tire-size mismatch can cause this — a smaller tire on one side reads higher speed.
Before you replace parts — try this first
C0070 on the Brakes system is most often mismatched tire sizes, uneven wear or low inflation on one side — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
The ABS lamp comes on, usually after driving at steady speed. ABS and traction control may be disabled until the code clears.
Common causes
- CommonMismatched tire sizes, uneven wear or low inflation on one side ($0–$800)
- CommonExcessive sensor air gap on one side ($50–$200)
- OccasionalDamaged tone ring on one side ($150–$600)
- RareWrong tone ring tooth count after a hub replacement ($150–$600)
How to fix
Check tire sizes, tread depth and inflation on both front wheels
When to use: First step
Reset both front sensors against their tone rings and compare live wheel speeds on a scan tool
When to use: When tires match
Inspect both tone rings and verify the tooth count matches spec
When to use: When the code persists or a hub was recently replaced
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → C0035 — Left Front Wheel Speed Sensor Circuit
- → C0036 — Left Front Wheel Speed Sensor Circuit Range/Performance
- → C0040 — Right Front Wheel Speed Sensor Circuit
- → C0041 — Right Front Wheel Speed Sensor Circuit Range/Performance
- → C0045 — Left Rear Wheel Speed Sensor Circuit
Frequently Asked Questions
Can I drive with code C0070?
C0070 is severity 3 — plan service within a few days. Performance is likely degraded already (you may feel reduced power, harsher shifts, or slightly worse fuel economy). Continuing to drive risks additional damage to adjacent components.
How much does it cost to fix C0070 on a commercial truck?
Total repair cost ranges varies depending on the root cause. The cheapest fix is usually the first one listed below — Mismatched tire sizes, uneven wear or low inflation on one side — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will C0070 fail a DOT inspection?
C0070 is generally not a direct DOT inspection fail item by itself. Inspectors focus on safety-critical systems (brakes, steering, tires, lights, hours-of-service). However, the check engine light alone can trigger additional inspection scrutiny. Best practice: fix the code and clear it before a planned inspection.
What's the difference between C0070 and related codes?
C0070 is closely related to: C0035 (Left Front Wheel Speed Sensor Circuit), C0036 (Left Front Wheel Speed Sensor Circuit Range/Performance), C0040 (Right Front Wheel Speed Sensor Circuit), C0041 (Right Front Wheel Speed Sensor Circuit Range/Performance). These codes share the same subsystem (brakes) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only C0070 is set without the companions, the issue is more isolated.
How do I prevent C0070 from coming back after a repair?
For C0070 (Front Wheel Speed Sensor Asymmetric Output), prevention centers on the brakes system. Clean wheel speed sensors at every brake service. Inspect tone rings for cracks or rust. Keep ABS sensor harnesses away from chafe points. Don't drive through deep water that can flood the rear wheel-speed sensor connectors.