The Quick Answer above is the generic definition. What follows is the model-specific detail for the Chevrolet models that log U0121.
DTC/U0121·Chevrolet
U0121 on Chevrolet: Causes, Symptoms and Fix Cost
Quick Answer
High SeverityNot safe to driveChevrolet
U0121 on a Chevrolet means another module (usually the PCM or gateway) can no longer talk to the ABS control module over the CAN bus. ABS, traction control, and ESC are disabled until the fault is repaired.
Typical repair cost, all makes€32 - €1750
Connect any standard Bluetooth OBD2 adapter to your Chevrolet and Skanyx tells you what U0121 means on that engine, whether it is safe to keep driving, and what the fix should cost. Free on iPhone and Android.
Get Skanyx freeWhat does U0121 mean on a Chevrolet?
Chevrolet Silverado 1500
2007-2013 (GMT900, 5.3L Vortec)EBCM failures on GMT900 trucks are common enough that the module is the first suspect, not the last. A speedometer dropping to zero alongside U0121 is the tell-tale sign. Check the ground behind the left cylinder head before you commit to a module, because corrosion there produces the same fault.
What causes U0121 on a Chevrolet?
Beyond the generic causes listed on the main U0121 page, these are the patterns noted for Chevrolet models:
Chevrolet Silverado 1500Internal EBCM failure (Kelsey-Hayes 325 unit)
Chevrolet Silverado 1500Corroded G200 ground behind the left cylinder head
How to diagnose U0121 on a Chevrolet with OBD2
Follow these steps to pinpoint the root cause of U0121:
- Scan every module on the vehicle, not just the PCM. If only the ABS module fails to respond, the fault is localized to it, its wiring, or its power supply.
- Load-test or replace the battery first. Below about 11.5V many modules drop off the CAN bus and throw U-codes that mimic hardware failure.
- Pull the ABS fuse(s) per the wiring diagram and confirm continuity. Check any dedicated ABS relay in the underhood fuse box.
- Unplug the ABS module and inspect the connector for green corrosion, water, or backed-out pins. On trucks and SUVs the module sits exposed to road spray, so check this carefully.
- Back-probe the connector with the key on: verify battery voltage on the power pin(s) and less than 0.1V drop from the module ground pin to battery negative.
- Measure resistance across DLC pins 6 and 14 with the ignition off and the modules asleep. You should see roughly 60 ohms. 120 ohms means one terminating resistor is missing (a broken bus wire); much lower means a short.
- Scope CAN High and CAN Low at the ABS connector. No traffic with good power and ground confirms broken wiring between the module and the gateway.
- If power, ground, and CAN traffic are all present at the connector and the module still won't answer, replace or refurbish the module and code it to the vehicle.
How much does U0121 cost to fix on a Chevrolet? (EUR)
Estimated repair costs for U0121 in EUR, compiled across makes. Chevrolet costs typically sit in the middle of each range.
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
Codes related to U0121
These codes are often seen alongside U0121 or point to related issues, on any make:
Looking for the full U0121 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main U0121 guideSkanyx · Chevrolet
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