C1227

DTC C1227: Left Rear Excessive Wheel Speed Sensor Variation (Part 1 Of 2):

DTC C1227: Left Rear Excessive Wheel Speed Sensor Variation (Part 2 Of 2):

DTC C1227 Schematic:

Circuit Description
As a toothed ring passes by the wheel speed sensor, changes in the electromagnetic field cause the wheel speed sensor to produce a small AC voltage signal whose frequency is proportional to wheel speed.

Conditions for Setting the DTC
This DTC will set when the following conditions are met:
^ The EBCM detects a sudden change in the left rear wheel speed determined to be unreasonable.
^ This DTC will not set if DTC C1234 has already failed.
^ This DTC can only be set when the stoplamp switch is open.

Action Taken When the DTC Sets
A malfunction DTC is stored, ABS is disabled, and the amber ABS indicator lamp is turned ON.

Conditions for Clearing the DTC
6 Conditions for the malfunction are no longer present and the Tech 2 scan tool Clear DTC Information function is used.
^ One hundred drive cycles have passed with no malfunctions detected.

Diagnostic Aids
The following list contains items that need to be inspected when diagnosing this system:
^ Loose wheel speed sensor.
^ Worn suspension components. Wheel speed sensor physically damaged.
^ Wheel speed sensor ring damaged.

The frequency of the malfunction can be checked by using the Enhanced Diagnostic function of the Tech 2 scan tool, as described in Enhanced Diagnostics.

Any circuitry that is suspected of causing the intermittent complaint should be thoroughly checked for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wiring connections or physical damage to the wiring harness. A careful visual inspection of the toothed ring, bearing and wheel speed sensor for physical damage should also be performed. If DTC sets at the same mph every time and wheel speed variation is noted above this mph on the Tech 2 scan tool, the speed ring is most likely damaged. This can occur at any speed.
NOTE: Resistance of the wheel speed sensor will increase with an increase in sensor temperature.

When measuring for a short to ground in a wheel speed sensor wiring circuit, manually switch the J 39200 (Digital Multimeter) to the Meg-Ohms range. This will ensure a high resistance short to ground can be found.


Test Description
The numbers below refer to step numbers on the diagnostic table.
3. Checks for excessive wheel bearing play.
6. Checks the wheel speed sensor resistance.
7. Checks voltage output of the wheel speed sensor.
8. Ensures that the wheel speed sensor wires are not shorted together.
13. Checks the wheel speed sensor output compared to the other three.