DTC C0238 or C038 Wheel Speed Mismatch. GMC Truck Savana 2000

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2000 🢒 Savana 🢒 Brakes 🢒 Antilock Brake System 🢒 DTC C0238 or C038 Wheel Speed Mismatch

Circuit Description

The rate at which the wheel/vehicle speed sensor ring makes a full 360 degrees rotation is directly related to the circumference of the tire(s).

Conditions for Running the DTC

•	The ignition is ON.

•	The vehicle is moving at a speed greater than 24 km/h (15 mph) and less than 80 km/h (50 mph).

Conditions for Setting the DTC

The EBCM detects that one speed sensor signal is at least 10% greater than or less than the other speed sensor signals.

Action Taken When the DTC Sets

•	The ABS and BRAKE indicators are commanded on.

•	The ABS is disabled for the remainder of the ignition cycle.

Conditions for Clearing the DTC

•	Repair the condition(s) responsible for setting the DTC.

•	Use the scan tool in order to clear the DTC.

Installing one front tire or one rear tire of significantly different size on the vehicle will set DTC C0238. Operating the vehicle with a tire that has very low air pressure may also set this DTC. Inspect the vehicle for an incorrect or damaged wheel speed sensor(s) or vehicle speed sensor if the tires and the EBCM and VCM/PCM calibrations are OK.

Test Description

If the front tires are not the same size as the rear tires, the EBCM calibration must match the FRONT tire size and the VCM/PCM calibration must match the REAR tire size.

Step	Action	Value(s)	Yes	No
1	Did you perform the ABS Diagnostic System Check?	--	Go to Step 2	Go to Diagnostic System Check
2	Inspect both of the front tires on the vehicle to ensure that both tires are of equal size. Are both of the front tires of equal size?	--	Go to Step 3	Go to Diagnostic Aids
3	Inspect both of the rear tires on the vehicle to ensure that both tires are of equal size. Are both of the rear tires of equal size?	--	Go to Step 4	Go to Diagnostic Aids
4	Use a scan tool in order to verify that the EBCM and the VCM/PCM both have the correct tire size calibration. Refer to Scan Tool Diagnostics and VCM Replacement/Programming in Engine Controls-4.3L, VCM Replacement/Programming in Engine Controls - 5.0 - 5.7, Powertrain Control Module Replacement/Programming in Engine Controls - 6.5, or VCM Replacement/Programming in Engine Controls - 7.4. Did you find and correct the condition?	--	Go to Step 5	Go to Diagnostic Aids
5	Use a scan tool in order to clear the DTC(s). Road test the vehicle for 2 miles within the conditions for running the DTC as specified in the supporting text. Does the DTC set?	--	Go to Step 2	System OK