C1227

Circuit Description
As a toothed ring passes by the wheel speed sensor, changes in the electromagnetic field cause the wheel speed sensor to produce an AC voltage signal. The EBCM uses the frequency of the AC signal to calculate the wheel speed.

Conditions for Running the DTC
^ No wheel speed sensor circuit hardware malfunctions are present.
^ The brake switch is OFF.

Conditions for Setting the DTC
The EBCM detects a rapid variation in the wheel speed. The wheel speed changes by 16 km/h (10 mph) or more in 0.01 seconds. The change must occur 3 times with no more than 1 second between occurrences.

Action Taken When the DTC Sets
^ The EBCM stores a malfunction DTC.
^ The EBCM disables the ABS and ETS.
^ The ABS warning indicator turns ON.
^ The TRAC OFF indicator turns ON.

Conditions for Clearing the DTC
^ The condition responsible for setting the DTC no longer exists and the Scan Tool Clear DTCs function is used.
^ 100 drive cycles pass with no DTCs detected. A drive cycle consists of starting the vehicle, driving the vehicle over 16 km/h (10 mph), stopping and then turning the ignition OFF.

Diagnostic Aids
Thoroughly inspect the wiring and the connectors. An incomplete inspection of the wiring and the connectors may result in a misdiagnosis, causing a part replacement with the reappearance of the malfunction.
The following are possible causes of the malfunction:
^ Poor connections
^ Broken wire insulation
^ A break in the wire inside the insulation
^ Loose or damaged toothed ring
^ Loose or damaged hub/bearing assembly
If an intermittent malfunction exists, refer to Testing for Intermittent and Poor Connections.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
4. This step tests the wheel speed sensor for the proper resistance value. This step ensures that the wheel speed sensor generates the proper voltage.
7. This step tests whether the wheel speed sensor circuits are shorted together.





DTC C1227 LR Excessive Wheel Speed Variation