03 Blazer. Truck became increasingly difficult to shift out of park, now won't at all. Also tail light brake lights don't work. High center mount brake light does work. So I tried replacing the brake light switch at the pedal. Shift problem seemed to be fixed at first, but now won't shift again. Brake lights still don't work either. Any suggestions on how to proceed?

 

It wont be the brake switch on the pedal because it control all of the brake lights. That said, the third top brake light is controlled directly by the pedal switch but the normal rear brake light signal passes through the MF switch and a different set of fuses.

1. Have you checked all of the relevant fuses?
2. Is there any history on the MF switch?

George

 

Another thought. The shift interlock solenoid is controlled by the pedal brake switch but on a different wire than the lower or upper brake lights. When you were down there replacing the brake light switch did you get a good look at the connector and the wires/looms exiting the switch?

George

 

The multi function switch (turn signal stalk) was replacing several months ago because the turn signal stopped working.

When I replaced the brake light switch, I did take a look at the connector. It looked normal, as did the bundle of wiring going to it. I only attempted to remove a little of the electrical tape though. Under the portion I did remove I didn't see any broken wires.
I did a visual check of what I thought were all relevant fuses, did not see any blown.

 

There are a lot of possibilities here and a meter and some testing may be required to get to the bottom of it. Since you replace the multi function switch, that’s a possibility a lot of aftermarket parts are crap. If the shift solenoid problem started after the new brake pedal switch then that switch is suspect. if the solenoid problem was before the new brake switch, then the wiring or the solenoid is suspect. Since you know how to open up the column, the first thing we should probably do is get a lead on that solenoid positive wire and see if it gets voltage when you press the brake pedal . Let me know if you need help with that.

Regarding the multi function switch, we need to get a meter lead on the output from the switch heading to the lower brake lights and see if the brake signal passes through when you press the pedal. If not, then get a meter lead on the input to the multi function switch and see if the brake pedal signal makes it to the switch. Again, let me know if you need help with the wire colors and so forth.

Don’t forget to check the fuses for those lower, brake, pedal light, the ones after the multi function switch. You might’ve shorted something when you were in the column.

George

 

Would the MF switch be suspect even though this truck has a floor shifter? This is the first time I've had to do anything with this system so I'm unfamiliar. Probably won't get time to work on it until next weekend, I have a heavy work schedule.

Appreciate you taking the time to respond!

 

The multi function switch is suspect for the lower rear brake lights. Is this a two or four-door?

George

 

Two door

 

When you’ve got the time, go grab a meter and let me know and I’ll walk you through finding your problem.

George

 

Thank you so much George.

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