Here is the fault tree for C1248, It basically states that there are other faults within the ABS/TCS system: DTC C1248
The dynamic rear proportioning (DRP) is a control system that replaces the hydraulic proportioning function of the mechanical proportioning valve in the base brake system. The DRP control system is part of the operating software in the EBCM. The DRP uses active control with the existing ABS in order to regulate the vehicle's rear brake pressure.
Conditions for Running the DTC
One or more faults have been detected by the EBCM in the ABS/TCS systems.
Conditions for Setting the DTC
One of the following conditions exists: " DTC C1214, C1217, C1237, C1254, C1255, C1261-1268, or C1271-1274 sets.
" DTC C1236 sets and the system voltage is less than 8.5 volts.
" Two wheel speed sensor DTCs on the same axle set.
Action Taken When the DTC Sets
" The EBCM disables the DRP for the duration of the ignition cycle.
" The red Brake warning indicator turns ON.
Conditions for Clearing the DTC
" The condition for the DTC is no longer present and the DTC is cleared with a scan tool.
" The EBCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.
" Use this DTC in order to differentiate which of the following conditions is present: - The EBCM turned ON the red Brake warning indicator.
- The instrument cluster turned ON the red Brake warning indicator due to low brake fluid in the master cylinder reservoir.
- The instrument cluster turned ON the red Brake warning indicator due to the application of the park brake.
" Diagnose any other ABS DTCs that set along with this DTC.
The number below refers to the step number on the diagnostic table.
Verifies whether other ABS/TCS/VSES DTCs are set.
Schematic Reference: Antilock Brake System Schematics
Did you perform the ABS Diagnostic System Check?
Go to Step 2
Go to Diagnostic System Check - ABS
Install a scan tool.
Turn ON the ignition, with the engine OFF.
Select the display DTCs function on the scan tool for the EBCM.
Does the scan tool display any ABS/TCS/VSES DTCs?
Go to Diagnostic Trouble Code (DTC) List
Go to Step 3
Use the scan tool in order to clear the DTCs.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC reset?
Go to Step 2
Perform the code check procedure again, this time select all modules-codes(not all clear codes). I can't remember right now, if there is TCS as a selection. If there is, that is where your codes might reside. Notice, that one of the conditions for setting the code in the above chart, is two wheel speed sensor DTC's for the same axle. This all occurred after the rear brakes were done, correct? Have you verified that those sensors are plugged in?