C1226 Excessive wheel speed variation at one front wheel (GM)

C1226 ABS excessive wheel speed sensor variation, right front (GM)

C1226 in short

On Chevrolet, C1226 means the ABS computer sees excessive speed variation from the right front wheel speed sensor. The ABS and traction control lights come on and the systems may stop working or act unexpectedly. Normal brakes still work, but have it inspected soon, and stop if the red brake light is on.

The ABS computer compares the speed signal from each wheel. If one wheel signal jumps around far more than the others while driving, it sets an excessive variation code for that wheel. On the GM readout in a 2002 Impala complaint, C1226 is the right front.

GM lists C1225, C1226, C1227 and C1228 together in a 1998-1999 minivan bulletin, which shows these four share one diagnostic table. The same code also shows up on older Cadillac models in a GM bulletin about the ABS light and unwanted ABS or traction control activation.

This page covers only what is sourced for Chevrolet. Other makes also use C1226, and a Ford Windstar complaint lists it, but no Ford meaning was verified here, so none is given.

Pick your make

C1226 is a manufacturer-specific code: its meaning depends on who built the car.

Other makes: meaning not verified. Check with a scan tool that reads manufacturer definitions.

Most likely causes

  1. Noisy or weak right front wheel speed signal

    Supported by vehicle data
    Why it ranks here
    The code is defined as excessive variation in the wheel speed signal, and GM revised its diagnostic tables for it, so the sensor, its ring and its wiring are where the table sends a technician.
    What would change this
    Rises if live wheel speed data shows the right front dropping out or spiking against the other wheels. Falls if all four wheels read steadily and the fault does not return.

  2. ABS control module or hydraulic unit fault

    Possible — needs testing
    Why it ranks here
    A Cadillac bulletin and owner complaints show C1226 stored with unwanted ABS activation and other ABS codes, but none of them name the module as the cause.
    What would change this
    Rises only after the wheel speed circuit tests good. Falls if a repaired sensor or wiring clears the code.
    How to test the brake system control module (abs module)

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Have the ABS module read with a scan tool that shows individual wheel speeds, and note every stored ABS code and when the fault appeared.

    Best left to a shopTool: scan tool with ABS live data

    Warning:Brake and ABS work affects your ability to stop. Leave testing and repair to a qualified shop.

Symptoms

  • ABS light on
  • Traction control light on or traction control acting when roads are dry
  • Pedal pulsing or ABS activating at low speed without hard braking
  • Red brake warning light on or the pedal feels different Gets more serious: stop and have it checked.

How to fix

This is a safety-critical system, so we explain the code but don't give repair steps. Have it inspected by a qualified technician.

Parts and cost context

  • Brake system control module (ABS module):Replacing the ABS module is a last step after the wheel speed circuit has been tested. Labor varies; get a quote.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Chevrolet

  • 1998–1999 · Venture

    Supported by vehicle data

    GM's 1998-1999 minivan bulletin covers the Venture and revises its diagnostic table for C1226 and the other excessive wheel speed variation codes.

  • 2002 · Impala

    Supported by vehicle data

    A 2002 Impala complaint lists C1226 as right front excessive wheel speed sensor variation, along with C1225 left front and front wheel speed circuit codes.

  • 010525006Status unverified

    Excessive wheel speed variation diagnostic tables revised (C1225 to C1228)

    1998–1999venture · issued · NHTSA 624109

    Revises steps 13 and 15 of the excessive wheel speed variation diagnostic tables in the ABS section of the service manual. The NHTSA summary does not describe a repair part.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Cadillac

  • 1997–1999 · Deville

    Supported by vehicle data

    GM bulletin 3300 covers an ABS light with C1226 on the DeVille. Meaning of the code on Cadillac was not separately verified.

  • 3300Status unverified

    ABS light on with C1226 or unwanted ABS or TCS activation

    1996–1999deville, eldorado · issued · NHTSA 10017254

    Service information for an ABS light with C1226, or unwanted ABS or traction control activation. The NHTSA summary does not say what the repair is.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

No curated relationships for C1226 yet.

All ABS, traction and stability control codes

Sources and review

  1. GM bulletin 01-05-25-006: excessive wheel speed variation diagnostic tables (C1225, C1226, C1227, C1228), 1998-1999 minivans — General Motors via NHTSA ,
  2. GM bulletin 3300: ABS light on with C1226 or unwanted ABS or TCS activation, Cadillac DeVille, Eldorado, Seville — General Motors via NHTSA ,
  3. Toyota Camry Owner's Manual (OM06291U) — Toyota
  4. NHTSA complaint ODI 10224551 (2002 Chevrolet Impala, C1226 readout) — NHTSA Office of Defects Investigation (consumer complaint)
Last reviewed
Written by
Saurabh K.
Editorial review
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This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error

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