Possible Causes

Circuit open
Circuit shorted
Brake fluid level switch (integral to the brake fluid reservoir)
ABS module

CAUTION:

Use the Flex Probe Kit for all test connections to prevent damage to the wiring terminals. Do not use standard multimeter probes.

DTC C1187 - BRAKE FLUID LEVEL INPUT CIRCUIT OPEN - PINPOINT TEST REFERENCE

PINPOINT TEST 8		DTC C1187 - BRAKE FLUID LEVEL INPUT CIRCUIT OPEN
STEP	INSPECTION		ACTION
1	CHECK ABS MODULE OPERATION Disconnect: Brake fluid level switch 0413-106. Connect a fused (10A) jumper wire between the brake fluid level switch circuit (GY/V), harness side and the brake fluid level switch circuit (Y/GY), harness side. Connect: IDS or equivalent tester. Key ON. Using the IDS or equivalent tester, clear the DTCS and repeat the self-test with the brake pedal not applied. Retrieve the DTCs. Is DTC C1187 retrieved again?	Yes	Go to next step.
1		No	Install a new brake master cylinder. See BRAKE MASTER CYLINDER , . Clear the DTCs. Repeat the self-test with the brake pedal not applied.
2	CHECK CIRCUIT (GY/V) AND 531 (Y/GY) FOR AN OPEN Key OFF. Disconnect: ABS control module connector. Measure the resistance between: ABS module circuit (GY/V), harness side and brake fluid level switch circuit (GY/V), harness side. ABS module circuit (Y/GY), harness side and brake fluid level switch circuit (Y/GY), harness side. Are the resistances less than 5 ohms?	Yes	Go to next step.
2		No	Repair the affected circuits) for an open. Clear the DTCs. Repeat the self-test with the brake pedal not applied.
3	CHECK CIRCUIT (GY/V) AND (Y/GY) FOR A SHORT TO GROUND Measure the resistance between ground and: ABS module circuit (GY/V), harness side. ABS module circuit (Y/GY), harness side. Is the resistance greater than 10,000 ohms?	Yes	Go to next step.
3		No	Repair the affected circuits) for a short to ground. Clear the DTCs. Repeat the self-test with the brake pedal not applied.
4	CHECK FOR CORRECT ABS MODULE OPERATION Disconnect all ABS connector. Check for: corrosion. pushed-out pins. spread terminals. Connect all ABS connector and make sure it is seated correctly. Operate the system and verify the concern is still present. Is the concern still present?	Yes	Install a new ABS module. see ANTI-LOCK BRAKE SYSTEM (ABS) MODULE . Test the system for normal operation.
4		No	The system is operating correctly at this time. Concern may have been caused by a loose or corroded connector. Clear the DTCs. Repeat the self-test with the brake pedal not applied.