Parking brake warning light ON - fixed
Thread Starter
Junior Member
Joined: Nov 2011
Posts: 12
Likes: 10
Parking brake warning light ON - fixed
I had the my parking brake warning light on(on the dash) continuously for a few weeks until I finally dove in to fix it.
Mine turned out to be a corroded wire going from the brake fluid level switch to the BCM. I spliced it back together and life is good. The following is just for info for anyone searching around.
There are a few things that keep this light on:
Brake fluid level low(or float or wiring)
Parking brake on(or switch or wiring)
ABS system
Body Control Module fault(need a new one)
From the service manual:
The Instrument Panel Cluster (IPC) uses 3 basic messaged inputs to control the brake warning indicator. The
first two are the parking brake warning indicator switch and the brake fluid level switch. The third is for the
Electronic Brake Distribution (EBD) function controlled by the ABS module. The parking brake warning
indicator switch and the brake fluid level switch status are sent from the Body Control Module (BCM) over
the High Speed Controller Area Network (HS-CAN). The EBD message is sent from the ABS module over
the HS-CAN .
The parking brake warning indicator switch is hardwired to the BCM through a single signal circuit while
using a separate ground to control the input. The brake fluid level switch is hardwired to the BCM through
separate signal and return circuits while using a separate ground to control the input.
The BCM provides a reference voltage to both the parking brake warning indicator switch and the brake fluid
level switch. When the parking brake is applied, the parking brake warning indicator switch closes to ground,
pulling the parking brake signal circuit low. When a low brake fluid level condition exists, the brake fluid
level switch closes to ground, pulling the signal and return circuits low. If the brake fluid level switch is
disconnected, the BCM reference voltage sent to the brake fluid level switch is sent high and the BCM sets
DTC B1048:01. When the BCM detects either the brake fluid level signal or the parking brake signal circuits
low, or the brake fluid level signal and return circuit high, the BCM sends the IPC a brake warning indicator
on request.
When the ABS module detects a base brake system concern or other ABS related concerns that affect the
EBD function, the ABS module sends a brake warning indicator on request to the IPC to illuminate the brake
warning indicator and the ABS warning indicator.
If the brake fluid level or parking brake status 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 known good message received. If
the brake fluid level or parking brake status messages are missing for more than 5 seconds, the IPC sets DTC
U0140:00 and defaults the brake warning indicator on. If the IPC does not receive the ABS status message or
the EBD message from the ABS module for more than 5 seconds, the IPC sets DTC U0121:00 and defaults
Hope this sends someone in the right direction.
The biggest thing that helped me was getting Forscan(free software at www.forscan.org) to be able to actually read the codes from the BCM.
The factory service manual is also invaluable when doing electrical testing as you don't have to trace wires all day long.
Just doing my part to give back to this community.
Mine turned out to be a corroded wire going from the brake fluid level switch to the BCM. I spliced it back together and life is good. The following is just for info for anyone searching around.
There are a few things that keep this light on:
Brake fluid level low(or float or wiring)
Parking brake on(or switch or wiring)
ABS system
Body Control Module fault(need a new one)
From the service manual:
The Instrument Panel Cluster (IPC) uses 3 basic messaged inputs to control the brake warning indicator. The
first two are the parking brake warning indicator switch and the brake fluid level switch. The third is for the
Electronic Brake Distribution (EBD) function controlled by the ABS module. The parking brake warning
indicator switch and the brake fluid level switch status are sent from the Body Control Module (BCM) over
the High Speed Controller Area Network (HS-CAN). The EBD message is sent from the ABS module over
the HS-CAN .
The parking brake warning indicator switch is hardwired to the BCM through a single signal circuit while
using a separate ground to control the input. The brake fluid level switch is hardwired to the BCM through
separate signal and return circuits while using a separate ground to control the input.
The BCM provides a reference voltage to both the parking brake warning indicator switch and the brake fluid
level switch. When the parking brake is applied, the parking brake warning indicator switch closes to ground,
pulling the parking brake signal circuit low. When a low brake fluid level condition exists, the brake fluid
level switch closes to ground, pulling the signal and return circuits low. If the brake fluid level switch is
disconnected, the BCM reference voltage sent to the brake fluid level switch is sent high and the BCM sets
DTC B1048:01. When the BCM detects either the brake fluid level signal or the parking brake signal circuits
low, or the brake fluid level signal and return circuit high, the BCM sends the IPC a brake warning indicator
on request.
When the ABS module detects a base brake system concern or other ABS related concerns that affect the
EBD function, the ABS module sends a brake warning indicator on request to the IPC to illuminate the brake
warning indicator and the ABS warning indicator.
If the brake fluid level or parking brake status 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 known good message received. If
the brake fluid level or parking brake status messages are missing for more than 5 seconds, the IPC sets DTC
U0140:00 and defaults the brake warning indicator on. If the IPC does not receive the ABS status message or
the EBD message from the ABS module for more than 5 seconds, the IPC sets DTC U0121:00 and defaults
Hope this sends someone in the right direction.
The biggest thing that helped me was getting Forscan(free software at www.forscan.org) to be able to actually read the codes from the BCM.
The factory service manual is also invaluable when doing electrical testing as you don't have to trace wires all day long.
Just doing my part to give back to this community.
LONG TIME FORD GUY
Joined: Aug 2012
Posts: 882
Likes: 136
From: Lemoore, CA
I am fighting this right now. 2005 XLT. it seems completely random now staying on for a while then blinking randomly to off for a couple days. I sat in my truck a little while ago with the engine off and key on. the light was blinking randomly. Any body got a schematic of the circuit mentioned above? I should have my 2015 next month just don't want to trade it in with this stupid light on.
Senior Member
Joined: Dec 2014
Posts: 124
Likes: 30
From: Toronto, Ontario
I had the same problem with my 2006. It turned out to be a weak connection on the guage cluster. When you are looking at the cluster it was the top left connector. Just a slight wiggle would fix it. Cleaned it with electrical spray and now works fine.
Junior Member
Joined: Jan 2025
Posts: 4
Likes: 0
From: Camp Verde, AZ
Signal voltage
I had the my parking brake warning light on(on the dash) continuously for a few weeks until I finally dove in to fix it.
Mine turned out to be a corroded wire going from the brake fluid level switch to the BCM. I spliced it back together and life is good. The following is just for info for anyone searching around.
There are a few things that keep this light on:
Brake fluid level low(or float or wiring)
Parking brake on(or switch or wiring)
ABS system
Body Control Module fault(need a new one)
From the service manual:
The Instrument Panel Cluster (IPC) uses 3 basic messaged inputs to control the brake warning indicator. The
first two are the parking brake warning indicator switch and the brake fluid level switch. The third is for the
Electronic Brake Distribution (EBD) function controlled by the ABS module. The parking brake warning
indicator switch and the brake fluid level switch status are sent from the Body Control Module (BCM) over
the High Speed Controller Area Network (HS-CAN). The EBD message is sent from the ABS module over
the HS-CAN .
The parking brake warning indicator switch is hardwired to the BCM through a single signal circuit while
using a separate ground to control the input. The brake fluid level switch is hardwired to the BCM through
separate signal and return circuits while using a separate ground to control the input.
The BCM provides a reference voltage to both the parking brake warning indicator switch and the brake fluid
level switch. When the parking brake is applied, the parking brake warning indicator switch closes to ground,
pulling the parking brake signal circuit low. When a low brake fluid level condition exists, the brake fluid
level switch closes to ground, pulling the signal and return circuits low. If the brake fluid level switch is
disconnected, the BCM reference voltage sent to the brake fluid level switch is sent high and the BCM sets
DTC B1048:01. When the BCM detects either the brake fluid level signal or the parking brake signal circuits
low, or the brake fluid level signal and return circuit high, the BCM sends the IPC a brake warning indicator
on request.
When the ABS module detects a base brake system concern or other ABS related concerns that affect the
EBD function, the ABS module sends a brake warning indicator on request to the IPC to illuminate the brake
warning indicator and the ABS warning indicator.
If the brake fluid level or parking brake status 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 known good message received. If
the brake fluid level or parking brake status messages are missing for more than 5 seconds, the IPC sets DTC
U0140:00 and defaults the brake warning indicator on. If the IPC does not receive the ABS status message or
the EBD message from the ABS module for more than 5 seconds, the IPC sets DTC U0121:00 and defaults
Hope this sends someone in the right direction.
The biggest thing that helped me was getting Forscan(free software at www.forscan.org) to be able to actually read the codes from the BCM.
The factory service manual is also invaluable when doing electrical testing as you don't have to trace wires all day long.
Just doing my part to give back to this community.
Mine turned out to be a corroded wire going from the brake fluid level switch to the BCM. I spliced it back together and life is good. The following is just for info for anyone searching around.
There are a few things that keep this light on:
Brake fluid level low(or float or wiring)
Parking brake on(or switch or wiring)
ABS system
Body Control Module fault(need a new one)
From the service manual:
The Instrument Panel Cluster (IPC) uses 3 basic messaged inputs to control the brake warning indicator. The
first two are the parking brake warning indicator switch and the brake fluid level switch. The third is for the
Electronic Brake Distribution (EBD) function controlled by the ABS module. The parking brake warning
indicator switch and the brake fluid level switch status are sent from the Body Control Module (BCM) over
the High Speed Controller Area Network (HS-CAN). The EBD message is sent from the ABS module over
the HS-CAN .
The parking brake warning indicator switch is hardwired to the BCM through a single signal circuit while
using a separate ground to control the input. The brake fluid level switch is hardwired to the BCM through
separate signal and return circuits while using a separate ground to control the input.
The BCM provides a reference voltage to both the parking brake warning indicator switch and the brake fluid
level switch. When the parking brake is applied, the parking brake warning indicator switch closes to ground,
pulling the parking brake signal circuit low. When a low brake fluid level condition exists, the brake fluid
level switch closes to ground, pulling the signal and return circuits low. If the brake fluid level switch is
disconnected, the BCM reference voltage sent to the brake fluid level switch is sent high and the BCM sets
DTC B1048:01. When the BCM detects either the brake fluid level signal or the parking brake signal circuits
low, or the brake fluid level signal and return circuit high, the BCM sends the IPC a brake warning indicator
on request.
When the ABS module detects a base brake system concern or other ABS related concerns that affect the
EBD function, the ABS module sends a brake warning indicator on request to the IPC to illuminate the brake
warning indicator and the ABS warning indicator.
If the brake fluid level or parking brake status 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 known good message received. If
the brake fluid level or parking brake status messages are missing for more than 5 seconds, the IPC sets DTC
U0140:00 and defaults the brake warning indicator on. If the IPC does not receive the ABS status message or
the EBD message from the ABS module for more than 5 seconds, the IPC sets DTC U0121:00 and defaults
Hope this sends someone in the right direction.
The biggest thing that helped me was getting Forscan(free software at www.forscan.org) to be able to actually read the codes from the BCM.
The factory service manual is also invaluable when doing electrical testing as you don't have to trace wires all day long.
Just doing my part to give back to this community.
Junior Member
Joined: Jan 2025
Posts: 4
Likes: 0
From: Camp Verde, AZ
brake light issues
New member here. 2009 f150 4X4 platinum 210K. Came back from vacation and battery was dead. Replaced battery but both red brake lights on the IC were lit up, bell dings for first mile of driving and cruise control won't work and message board says "parking brake engaged". Replaced park brake switch, no change. Took it to dealership. They showed park brake wire shorted to ground, but said the BCM needed to be replaced but is no longer available through Ford. Sent the BCM to company in NY to fix. Put it back in and same issue. Got forscan and connector. cut the wire to park brake switch at BCM and no more code. Brake lights in IC still on and same symptoms. Anyone on here have suggestions?
Thanks
Thanks