OBD-II Diagnostic Trouble Code
C0043 — Left Rear Wheel Speed Sensor Circuit Open
C0043 is set when the ABS module detects an open circuit in the left rear wheel speed sensor. The module saw a resistance or bias voltage consistent with a broken sensor loop. On tandem trucks, which rear axle the sensor sits on depends on the ABS configuration.
Severity 4/5
Truck-relevant
Stop within 50 mi
Severity
Stop within 50 mi
Left Rear Wheel Speed Sensor Circuit Open
Code
C0043
Category
Chassis
Subsystem
Speed
Truck-relevant
Yes
What this means for truckers
C0043 (Left Rear Wheel Speed Sensor Open) — same diagnosis as front sensors but harness routing differs.
Before you replace parts — try this first
C0043 on the Speed system is most often broken sensor lead or extension cable along the axle — 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 is on and ABS, and often automatic traction control, is disabled or limited. Normal service brakes still work.
Common causes
- CommonBroken sensor lead or extension cable along the axle ($80–$300)
- CommonFailed sensor (open coil) ($100–$300)
- OccasionalLoose or corroded connector ($50–$200)
- RareFaulty ABS module input ($600–$2000)
How to fix
Measure sensor resistance at the connector and at the module
When to use: First step
Repair the lead or extension cable
When to use: When the wiring is damaged
Replace the sensor and spring clip
When to use: When the sensor reads open
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 C0043?
Drive with caution. C0043 is severity 4 — stop within ~50 miles. Most commercial diesel codes at this severity (turbo, fuel rail, transmission solenoid) can damage adjacent expensive components if left unrepaired. Get to a service location before highway-speed loads.
How much does it cost to fix C0043 on a commercial truck?
Total repair cost ranges $50–$2000 depending on the root cause. The cheapest fix is usually the first one listed below — Broken sensor lead or extension cable along the axle — 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 C0043 fail a DOT inspection?
C0043 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 C0043 and related codes?
C0043 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 (speed) 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 C0043 is set without the companions, the issue is more isolated.
How do I prevent C0043 from coming back after a repair?
For C0043 (Left Rear Wheel Speed Sensor Circuit Open), prevention centers on the speed system. Inspect wheel speed sensor wiring at PM (rodents love it). Keep ABS tone rings clean.