Code C1446 Brake Light Switch Circuit Fault

ETS · September 7, 2011

Moderator, If this is wrong area please move it for me. I have a 2006 F250 5.4 gas, Automatic, 4x4, XL, Reg Cab. This is a FED-EX Delivery Truck. That has intermittent C1446. Light will go on and off during his normal daily route say twice a week. I have road tested this truck numerous times and cannot duplicate the problem. Have replaced brake light switch, Inspected connectors everywhere in circuit including at ABS Module. Double checked E Brake Light Switch, Traced harness for chaffing even switched another cluster from an identical truck. Code still comes back. Driver says brake lights work when light is on. But this is not nessesarily good information. These trucks get run HARD on rough mountian roads. Rain or moisture has no effect. Does it rain or shine. Has anyone had a problem like this? Can you give me any ideas or possibly a flow chart to follow? I have a set factory shop manuals here. Any input will be greatly appriciated. This one has me stumped and frustrated!

Brad Clayton · September 7, 2011

The brake pedal position swith and or the low fluid level switch in the master can set this code. It seems you have ruled out the BOO switch, so I would concentrate on the low level switch.

Aside from doing a good visual inspection of the wiring at the master cylinder, the easiest thing to do is to clear the code and jump out the switch. If you can't drive it long enough to get it to act up then let the customer know the switch is jumped out and let them drive it to see if the code returns. If it doesn't, then I would put my money on the master. If the code returns then you have some wiring issues to trace down, but I doubt that will be the case.

Unplug the connector on the side of the master and jump out pins 2 (red arrow) and 3 (green arrow).

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lmorris · September 8, 2011

IIRC the BOO switch has 2 positions, one for the lights and one for the BCM/PCM. I have seen a few that have lights working, but have other issues pertaining to the BOO switch.

ETS · September 14, 2011

I installed jumper and told driver to watch for light. It has run 4 days now with no light or code. Looks like that was it. I had inspected that circuit but was unsure how to jump the switch. Seen lots of bad ones on cars with 2 wire switch. First Super Duty with this issue. My thanks to Mr. Clayton.