Pinpoint Test O : The Brake Warning Indicator Is Always On: Notes

WARNING: This page is about a different car, the 2017 Lincoln Navigator and 2017 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.

Refer to Instrument Cluster for schematic and connector information.

Normal Operation and Fault Conditions

See Brake Warning Indicator, Parking Brake Position Switch and Brake Fluid Level Switch. Refer to Instrument Panel Cluster (IPC) .

NOTE: If DTC U0140:00 sets in the IPC, other symptoms can also be present such as TPMS, instrument panel backlighting, and door ajar indication. If DTC U0121:00 sets, other symptoms can also be present such as ABS warning indicator and traction control or traction control off indicators always on.

If the brake lamp request or the brake warning indicator request messages are missing for less than 5 seconds, the IPC defaults the brake warning indicator to its last state (on or off) based upon the last message received.

If the brake warning indicator request is missing for longer than 5 seconds, the IPC sets DTC U0140:00 and defaults the brake warning indicator on.

If the IPC does not receive the brake lamp request message from the ABS module for longer than 5 seconds, the IPC sets DTC U0121:00 and defaults the ABS warning indicator on.

BCM DTC Fault Trigger Conditions

DTC	Description	Fault Trigger Conditions
B1048:01	Brake Fluid Level Switch: General Electrical Failure	A continuous and on-demand DTC that sets in the BCM when the BCM detects an open or short to ground on the brake fluid level switch input.
B1048:7B	Brake Fluid Level Switch: Low Fluid Level	A continuous and on-demand DTC that sets in the BCM when the BCM detects low brake fluid level.
C1D00:11	Park Brake Apply Switch: Circuit Short To Ground	A continuous and on-demand DTC that sets in the BCM if the BCM detects a short to ground on the parking brake input circuit.

Possible Sources

Wiring, terminals or connectors
Parking brake position switch
Brake fluid level switch
ABS concern
BCM
IPC

Visual Inspection and Diagnostic Pre-checks

Verify the brake fluid level is full.
Inspect the base brake system and the parking brake system for correct operation.
Make sure the brake fluid level switch connector is connected and check for signs of connector terminal damage, corrosion or pushed out pins.
Inspect the brake fluid level switch wiring for signs of a cut or opened circuit. Inspect the brake fluid level switch for signs of any external damage.