OBD-II Diagnostic Trouble Code
C0801 — EBCM Vehicle Speed Output Loss
C0801 indicates the EBCM vehicle speed output was lost or is faulty. On some trucks the brake module sends vehicle speed to the engine, transmission or cluster, and this code sets when that output circuit or message fails. The meaning varies by OEM.
Severity 3/5
Truck-relevant
Service this week
Severity
Service this week
EBCM Vehicle Speed Output Loss
Code
C0801
Category
Chassis
Subsystem
Brakes
Truck-relevant
Yes
What this means for truckers
Service within a few days on a Cummins X15, Detroit DD15, PACCAR MX-13. Performance is likely degraded. Continuing to drive without service risks additional component damage.
Before you replace parts — try this first
C0801 on the Brakes system is most often wiring short or open in the speed output circuit — 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
Speedometer may not work, cruise control may not engage, and the engine or transmission may log speed codes. ABS lamp may be on. Some trucks will limit road speed or shift poorly without a speed signal.
Common causes
- CommonWiring short or open in the speed output circuit ($80–$300)
- OccasionalNetwork fault between modules ($100–$500)
- OccasionalFaulty receiving module input (cluster or ECM) loading the circuit ($200–$900)
- RareEBCM output driver failure ($700–$2000)
How to fix
Check for related codes in engine, transmission and cluster modules
When to use: First step
Test the speed output circuit for shorts and opens
When to use: Hardwired speed output
Disconnect receiving modules one at a time to find a loaded circuit
When to use: Output shorted to ground
Replace the EBCM
When to use: Circuit is good and output still missing
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
Frequently Asked Questions
Can I drive with code C0801?
C0801 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 C0801 on a commercial truck?
Total repair cost ranges $80–$2000 depending on the root cause. The cheapest fix is usually the first one listed below — Wiring short or open in the speed output circuit — 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 C0801 fail a DOT inspection?
C0801 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 C0801 and related codes?
There are no directly related codes in the standard catalog. Diagnose this code on its own merits and check for any companion codes the ECM may have stored alongside it.
How do I prevent C0801 from coming back after a repair?
For C0801 (EBCM Vehicle Speed Output Loss), 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.