A026

Code A026 Right Front Excessive Wheel Speed Variation






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 sinusoidal (AC) voltage whose frequency is proportional to wheel speed. The magnitude of this signal is directly related to wheel speed and the proximity of the wheel speed sensor to the toothed ring, often referred to as the air gap.

This code detects opens or a low output condition that cause intermittent wheel speed operation. Also detected is any sudden change in wheel speed determined to be unreasonable.

Test Description

Numbers below refer to circled numbers on the diagnostic chart.

1. This determines if Code A033 is present.
2. This test verifies whether the fault is currently present.
3. This step is designed to identify a wheel speed sensor or circuitry that is damaged and visably apparent.
4. This test checks to see that the wheel speed sensor circuitry is within proper resistance value.
5. This insures that the wheel speed sensor is not shorted to ground.
6. This step insures that the wheel speed sensor circuitry is not internally shorted.
7. This checks for an open in the wheel signal low circuit.
8. This checks for an open in the wheel signal high circuit.
9. This step insures that Code A026 was not set due to a poor connection between the world connector and EBCM.

Diagnostic Aids

An "intermittent" problem may be caused by a poor connection, rubbed through wire insulation, or a wire that is broken inside the insulation.

The frequency of the problem can be checked by using the enhanced diagnostic function of the "Scan" tool, as described in the "General Information."

If the customers comments reflect that the ABS Amber warning lamp is "ON" only during moist environmental changes, (rain, snow, vehicle wash) all wheel speed sensor circuitry should be thoroughly inspected for signs of water intrusion. If code is not current clear codes and simulate the effects of water intrusion. Use the following procedure. Spray down the suspected area with a 5% salt water solution (two teaspoons of salt to 12 oz. of water). Start vehicle, allow vehicle to run for 10 seconds. If code returns immediately, replace suspected harness.

Any circuitry, that is suspected as 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, CV joint, bearing and wheel speed sensor for physical damage should also be performed. If code sets at the same mph every time and wheel speed variation is noted above this mph on the Tech 1, the speed ring is most likely damaged. This can occur at any speed.