C037

C0237 or C037

CIRCUIT DESCRIPTION
The Electronic Brake Control Module (EBCM) receives the rear wheel speed signal from the Vehicle Control Module (VCM). The rear wheel speed signal originates from the Vehicle Speed Sensor (VSS) which is connected to the VCM.

CONDITIONS FOR SETTING THE DTC
^ Electronic Brake Control Module (EBCM) seeing the rear speed signal line drop out and return. This malfunction can be caused by a malfunction in the VSS, or a fault in CKT 1827.
^ The EBCM attempts to detect an erratic rear speed signal every 5 milliseconds. If the rear speed signal is missing for greater than 15 milliseconds while a vehicle speed greater than 32 km/h (20 mph) with brake applied, or 20 km/h (112 mph) with brake released a Diagnostic Trouble Code (DTC) C0237 will set. At this point the DTC will be condition latched. This means that the ABS system will be disabled and the ABS indicator lamp stays on as long as the condition exists. If the erratic DTC is set 3 consecutive times during the same ignition cycle, the DTC will set as an ignition latched DTC. This means that the ABS system will be disabled and the ABS indicator lamp stays on until the ignition is turned off; even if the fault goes away.

ACTION TAKEN WHEN THE DTC SETS
^ The ABS indicator lamp turns on
^ The ABS disables

Diagnostic Trouble Code (DTC) C0237 initially sets as a condition latched code. This means that the ABS system will be disabled and the ABS indicator lamp stays on as long as the condition exists. If the erratic DTC is set 3 consecutive times during the same ignition cycle, the DTC will set as an ignition latched DTC. This means that the ABS system will be disabled and the ABS indicator lamp stays on until the ignition is turned off; even it the fault goes away.

CONDITIONS FOR CLEARING THE DTC
^ Repair the conditions responsible for setting the Diagnostic Trouble Code (DTC)
^ Use the Scan Tool Clear DTCs function

DIAGNOSTIC AIDS
This Diagnostic Trouble Code (DTC) can be set by a malfunction in the VSS, or a fault in CKT 1827.
Before performing any diagnostics on the ABS, resolve any Vehicle Speed Sensor (VSS) DTC's currently set in the Vehicle Control Module (VCM).
In addition, any of the following conditions may cause an intermittent malfunction:
^ A poor connection
^ Wire insulation that is rubbed through
^ A wire breaks inside the insulation

Thoroughly check any circuitry that is suspected of causing the intermittent complaint for the following conditions:
^ Backed out terminals
^ Improper mating
^ Broken locks
^ Improperly formed or damaged terminals
^ Poor terminal to wiring connections
^ Physical damage to the wiring harness

TEST DESCRIPTION
The numbers below refer to the steps in the diagnostic table:
2. This step uses the voltage output from the Vehicle Control Module (VCM) to check the 1827 CKT.
3. This step checks the 1827 CKT for proper resistance.
5. This step checks for a short in the wiring between the Electronic Brake Control Module (ECBM) and the VCM.