Normal Operation

WARNING: This page is about a different car, the 2010 Mercury Mariner and 2010 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.

The wheel speed sensor and sensor ring generate a square wave signal to the ABS module that is proportional to wheel speed. The ABS module compares wheel speed inputs from all wheel speed sensors to determine an impending wheel lockup. Incorrect tire size can set these DTCs as well.

Voltage and ground signals are supplied to the wheel speed sensors from the ABS module. A difference in wheel speeds possibly caused by damaged wheel speed sensor rings, mismatched wheel sizes, driving on flat tires, an excessive wheel speed sensor air gap or a damaged tone ring will cause DTC C1233, C1234, C1235 or C1236 to set. Also an open or a short to voltage or ground in the sensor circuits will cause the appropriate DTC to set.

DTC FAULT TRIGGER CONDITIONS CHART

DTC Description	Fault Trigger Conditions
C1233 - Wheel Speed LF Input Signal Missing C1234 - Wheel Speed RF Input Signal Missing C1235 - Wheel Speed RR Input Signal Missing C1236 - Wheel Speed LR Input Signal Missing	When the vehicle speed exceeds 15 km/h (9 mph), if the ABS module does not receive a signal from the wheel speed sensor, the corresponding DTC will set.

This pinpoint test is intended to diagnose the following:

Wiring, terminals or connectors
Mismatched tire sizes
Wheel speed sensor tone ring
Wheel speed sensor
Wheel bearing
ABS module