What Does C0266 Mean?
C0266 indicates the Electronic Brake Control Module (EBCM) has detected a malfunction in its power relay circuit. The EBCM relay supplies power to the ABS/stability control system components, and this code means the module has detected an open circuit, short circuit, or excessive resistance in the relay control circuit. This prevents the EBCM from properly energizing the hydraulic pump motor and solenoid valves necessary for ABS and traction control operation.
Safety Warning
Not safe to drive normally as ABS, traction control, and stability control will be completely disabled. Vehicle will have conventional braking only with increased risk of wheel lockup during hard braking or loss of control on slippery surfaces. Repair immediately before driving in adverse conditions.
Common Causes
35%
Failed EBCM relay with burned or welded contacts, or internal coil failure
30%
Corroded, loose, or damaged wiring/connectors between EBCM and relay or relay and power source
20%
Blown fuse in EBCM relay power supply circuit or main ABS fuse
15%
Internal EBCM failure with faulty relay driver circuit or output stage
Diagnostic Steps
1
Step 1: Locate the EBCM relay (typically in underhood fuse/relay box) and inspect for physical damage, corrosion, or burning. Remove relay and check socket for corroded terminals, bent pins, or evidence of overheating.
2
Step 2: Using a digital multimeter, test the removed relay for proper resistance across coil terminals (typically 70-120 ohms) and verify contact continuity when 12V is applied to coil. Replace relay if readings are out of specification or contacts fail to close.
3
Step 3: With relay removed, check for battery voltage (12-14V) at relay socket power supply terminal with ignition on. Verify good ground at relay ground terminal (less than 0.5 ohms to battery negative).
4
Step 4: Using a multimeter on the relay control terminal, monitor voltage while a helper cycles ignition on/off. The EBCM should pull this terminal to ground (near 0V) when energizing relay. If voltage does not drop, suspect EBCM internal fault.
5
Step 5: Inspect all wiring between relay socket and EBCM connector for chafing, cuts, or pinched areas. Check EBCM connector terminals for corrosion, pushed-back pins, or moisture intrusion. Repair wiring/connectors as needed.
6
Step 6: After repairs, clear codes and perform functional test by driving vehicle above 15 mph to verify ABS/traction control system operates normally and code does not return.
Estimated Repair Cost
$150 - $800
Parts + labor, varies by vehicle and location
C0266 indicates the Electronic Brake Control Module (EBCM) has detected a malfunction in its power relay circuit. The EBCM relay supplies power to the ABS/stability control system components, and this code means the module has detected an open circuit, short circuit, or excessive resistance in the r...
The most common cause of C0266 (EBCM Relay Circuit) is: Failed EBCM relay with burned or welded contacts, or internal coil failure
Typical repair costs for C0266 range from $150 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Not safe to drive normally as ABS, traction control, and stability control will be completely disabled. Vehicle will have conventional braking only with increased risk of wheel lockup during hard braking or loss of control on slippery surfaces. Repair immediately before driving in adverse conditions.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C0266 to identify the root cause.
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Quick Info
Category
Chassis
System
Anti-lock Brake System (ABS) / Electronic Stability Control
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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