OBD-II Diagnostic Trouble Code
C0306 — EBCM Range/Performance
C0306 indicates a range or performance fault reported by the EBCM, often tied to the ABS pump motor or an internal check that did not perform as expected. The module saw a result outside expected limits during its self-test or operation. This code definition varies a lot by OEM, so confirm with the service information.
Severity 4/5
Truck-relevant
Stop within 50 mi
Severity
Stop within 50 mi
EBCM Range/Performance
Code
C0306
Category
Chassis
Subsystem
Brakes
Truck-relevant
Yes
What this means for truckers
Stop within ~50 miles on a Cummins X15, Detroit DD15, PACCAR MX-13. Driving longer risks damaging adjacent components (turbo housing, head gasket, aftertreatment) and turning a $300 fix into a $3,000 fix.
Before you replace parts — try this first
C0306 on the Brakes system is most often low system voltage or poor ebcm ground — 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
ABS, traction and stability lamps on and ABS likely disabled. Base braking remains. The fault may be intermittent and tied to low voltage or hot conditions.
Common causes
- CommonLow system voltage or poor EBCM ground ($60–$300)
- OccasionalWeak ABS pump motor ($800–$2500)
- OccasionalCorroded EBCM connector ($80–$250)
- OccasionalInternal EBCM failure ($700–$2000)
How to fix
Test batteries, charging and EBCM grounds
When to use: First step
Run pump motor and solenoid tests with a scan tool
When to use: To find which part fails
Check for software updates or OEM bulletins
When to use: Before replacing the module
Replace the EBCM / modulator and bleed
When to use: Fault confirmed internal
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 C0306?
Drive with caution. C0306 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 C0306 on a commercial truck?
Total repair cost ranges $60–$2500 depending on the root cause. The cheapest fix is usually the first one listed below — Low system voltage or poor EBCM ground — 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 C0306 fail a DOT inspection?
C0306 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 C0306 and related codes?
C0306 is closely related to: C0300 (Pump Motor Loop Open). 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 C0306 is set without the companions, the issue is more isolated.
How do I prevent C0306 from coming back after a repair?
For C0306 (EBCM Range/Performance), 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.