Brake On/Off Switch

[Drg racr]

My truck is flashing a code indicating I have a brake on/off switch not working. What is that? Is it on the brake pedal bracket? Also, does it do?
My cruise sometimes quits, so I bet that's the problem. Does it also control anything in the trans, like the lockup?

 

[Turdle]

I believe it is on the brake pedal. It switches the cruise control off, when brakes are applied.

 

[MrShorty]

Which code was it? The most common cause of a KOER 536 is the operator neglected to press the brake after engine id was output during the KOER test. CM 536 (without accompanying KOEO/KOER code) could indicate an intermittent fault in the BOO circuit. A KOEO 536 indicates a hard fault in the BOO circuit.

Remember that the code points to a problem in the entire circuit, not just the switch. Do your brake lights work correctly? As I recall, there is one switch on the brake pedal that does everything: lights, EEC-IV, and cruise.

 

[Glacier991]

The BOO is also used to control torque convertor lockup.

 

[BrooklynBay]

You could test the switch very easily with a continuity tester.

 

[Drg racr]

That has to be what it is. My Torque conv sometimes won't lockup, and my cruise sometimes won't work. But, they won't both fail at the same time! If one doesn't work, the other one will; freaky, huh?
I know it's a code 536 coming out of the computer, with the KOER test. Yes, the brake lights work fine.

 

[MrShorty]

As I noted above, the vast majority of the time, a KOER 536 is the result of operator error during the KOER test. If you know for certain that you pressed on the brake immediately after engine id was output (and the brake lights came on at that point), then it sounds like there could be a fault in the BOO circuit. If the brake lights are coming on, that suggests to me that the switch itself is good, and that the fault likely would be somewhere in the wiring to the EEC-IV computer and cruise computer/amplifier.

 

[Drg racr]

Sounds like this could be over my head. The lockup comes and goes intermittently, it will work for a day or two, then turn off for a day or two.The past couple weeks or so, the cruise has been working steadily. I might take it to a buddy and see if he can trace this down.