Chevrolet C0265 Code: EBCM Relay Circuit
The ABS module on many GM trucks found its built-in relay isn't delivering power, so ABS shuts down.
Safety first · Consult a professional
- Braking system affected: ABS may be disabled. Drive carefully and have it checked promptly.
At a glance
Severity: Moderate
- Meaning
- EBCM Relay Circuit
- System
- Brakes, ABS & Chassis · Chassis
- Safe to drive?
- With caution
- Typical repair cost
- $0–$1,100
- DIY difficulty
- Hard
C0265 is the classic ABS code on Chevrolet and GMC trucks and SUVs that use the frame-mounted Kelsey-Hayes electronic brake control module (EBCM), above all the 1999–2007 Silverado and Sierra, 2000–2006 Tahoe, Suburban and Avalanche, and related models. Inside the EBCM sits a relay that feeds battery voltage to the solenoid valves in the brake pressure modulator; when the module switches that relay on and the voltage on the output side stays low, it logs C0265 (GM's wording is typically 'relay circuit low when on'). On these trucks the fault is usually inside the module itself: cracked solder joints and a tired relay open up with heat, cold and vibration, which is why the code often comes and goes before it stays. Because the same module also handles dynamic rear proportioning, the red BRAKE light usually comes on along with the ABS light.
Can I keep driving? The service brakes still stop the truck, but ABS and rear brake proportioning control are off, so the rear wheels can lock earlier under hard braking, especially empty or on wet roads. Leave extra following distance and get it repaired rather than living with it.
How to read C0265
- C Chassis
- 0 Generic (SAE)
- 2 Brakes, ABS & Chassis
- 65 Specific fault
Symptoms
- ABS light and red BRAKE warning light on together
- Warnings appear after a cold start or on a hot day, then disappear after a restart
- Rear wheels lock more easily in a panic stop, especially with an empty bed
- Traction control or StabiliTrak light on, where equipped
- A single click from the module at key-on is missing or the lights come on right after it
- Code returns within a few drives after clearing
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Internal EBCM failure: cracked solder joints or worn contacts of the built-in relay
- Corroded EBCM ground or chassis ground near the module on the frame
- Weak battery, loose battery terminals or low charging voltage
- High-resistance ABS power feed: blown or poorly seated ABS fuse, corroded fuse terminal
- Corroded or loose pins in the EBCM harness connector (road salt and water on the frame rail)
Diagnosis step by step
Confirm the code and look at history
Use a scan tool that reads the GM EBCM. Note whether C0265 is current or history, and whether it's alone or accompanied by pump motor or voltage codes, which point to a supply problem rather than the relay.
Tools: OBD-II scanner
Check the battery and charging voltage first
A healthy battery rests around 12.6 V and the engine running should show roughly 13.5 to 14.8 V. Clean and tighten GM side-post terminals, because a loose battery connection can set EBCM relay codes on these trucks.
Tools: Multimeter
Inspect fuse, feed and ground
Check the ABS fuse in the underhood fuse block for a snug fit and heat marks. Follow the EBCM ground to the frame, remove it, clean it to bare metal and reinstall it with dielectric grease, then clear the code and retest.
Tools: Multimeter, Screwdriver, Soft brush
Measure power at the module under load
With the key on, back-probe the EBCM battery feed and ground at the connector. Compare the feed with battery voltage; more than about half a volt of difference, or a ground reading more than a few tenths of a volt above zero, means a wiring problem that must be fixed before condemning the module.
Tools: Multimeter
Inspect the EBCM connector on the frame
On these trucks the module sits under the driver's side, bolted to the modulator on the frame rail. Unplug the connector and look for green corrosion, pushed-out pins or a torn seal, then clean and reseat it.
Tools: Flashlight, Screwdriver
Decide between rebuild and replacement
If power, ground and connector are good and the code returns, the EBCM is the fault. The module unbolts from the modulator without opening the brake lines, so it can be sent to a rebuild service or replaced; a new unit may need to be set up for the truck with a capable scan tool.
Tools: Screwdriver, OBD-II scanner
Where the parts are
- 1Battery
- 2Alternator
- 3Engine computer (ECM)
- 4CAN bus
- 5Transmission
- 6Wheel speed sensor
- 7High-voltage battery
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Clean battery terminals and EBCM ground | Yes | $0–$120 |
| Repair ABS fuse terminal or EBCM connector pins | No | $60–$220 |
| Mail-in EBCM rebuild (remove and reinstall yourself) | Yes | $120–$300 |
| Remanufactured or new EBCM, installed and set up | No | $450–$1,100 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Emissions / smog test impact
Depends
C0265 lives in the ABS module and doesn't turn on the check engine light, so it doesn't fail an OBD emissions test. States with a safety inspection may fail a truck whose ABS or red BRAKE light stays on.
Frequently asked questions
Why is the red BRAKE light on with C0265?
On these GM trucks the EBCM also controls how much pressure goes to the rear brakes (dynamic rear proportioning). When it shuts down it turns on the red BRAKE light to warn that this function is gone. Still check the brake fluid level, but with C0265 stored the module is the usual reason.
How is C0265 different from C0121?
Both describe the power relay that feeds the ABS valves. C0265 is the number used on the older Kelsey-Hayes modules found on GM full-size trucks and SUVs, while C0121 is used on other GM brake modules. The diagnosis is similar, but the truck module's internal failure is much more common with C0265.
Can I just replace the relay?
Not as a separate part. The relay is soldered onto the circuit board inside the EBCM, so the practical options are a module rebuild, where the board is repaired and reinforced, or a replacement module.
Do I have to bleed the brakes after swapping the EBCM?
Usually not. The electronic module separates from the hydraulic modulator with a few screws, and the brake lines stay connected. Only if the modulator itself is replaced does the system need bleeding, often with a scan-tool bleed procedure.
The code only shows up sometimes. Can I ignore it?
It rarely fixes itself. Intermittent C0265 is typical of cracked solder joints that get worse with every heat cycle, and until then your ABS drops out without warning. Planning the repair is better than being surprised on a slippery road.
Sources
- Manufacturer public service information (cross-checked)
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