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Old 09-15-2021, 09:19 PM   #1
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Join Date: Jun 2012
Location: Glendora, CA
Posts: 4,048

2000 L-Series 2.2L Sedan
Default Does a failing brake light switch cause more than one problem?

The simple short answer is yes, it does. I replaced my brake light switch yesterday. This was a warranty part from Autozone - Duralast P/N DR 4109 (the A/Z part in their box was a GM part with the OE P/N molded on to it [90504499]). I can't recall how long ago this was, but the A/Z part replaced my factory original part some time less than four years ago. So the factory original part lasted a very long time.

Well, last Thursday, 9/9, a man in a vehicle passing by me to my right yelled out that my brake lights weren't working. I was on my way home from work. After completing some errands I'd arrived at home and checked the brake lights. I found that they were intermittently working but only when the brake pedal was depressed very hard.

Okay, I've got a bad switch. On Friday the Autozone clerk told me that they had to wait for a part found only at one of their warehouses. The replacement switch would arrive on the following Tuesday. (Oh great...I have to wait for this......the car is down until then.) The part arrived when promised and I installed it yesterday. Happily, the brake lights were now working as expected and as they always had. However, there was another benefit which came with installing a new brake light switch.

For several months I'd been having a problem when shifting out of Park. I would step on the brake pedal but could not shift out of park without depressing the pedal for several times. I thought that perhaps the BTSI (Brake Transmission Shift Interlock) solenoid was partially failing. That was wrong. The problem was being caused by the failing brake light switch. I am certain of this because I now no longer have make multiple depressions of the brake pedal to allow me to shift out of Park. So if you ever have a situation where you can't shift out of park normally and easily, it might be worth your while to replace the brake light switch.

In a somewhat unrelated subject the online cataloging of this part is problematic, though it need not be. Both AutoZone and RockAuto online catalogs show two stop light switches; one has four contacts and the other has two contacts. Curiously, both AutoZone and RockAuto have another category specifically for a cruise control release switch which turns out to be the same as the 4 prong brake light switch found in the other section. To make matters more confusing, the brake (or stop) light switch section does not differentiate between the purpose of the two and four contact switches. Why would this be? A cruise control release switch is not a brake light switch (or stop light switch [if you prefer]) as it does not engage the brake lights when turned off, nor does it interact electrically with the BTSI solenoid. Its primary interaction is with the cruise control box under the hood.

Sssooooo............ If you're ever asked by a parts person if the brake light switch on your L-Series car has two or four contacts, the answer here is TWO.
361K miles - Holy canolli!
Biden/Harris predictions, '21 -'25: weak economy; weakened military; increased terrorism; an emboldened RED CHINA. Sadly, B & H are proving me correct...too bad.
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