Could stop light switch assembly affect center mount brake lamp only?

unit00seven · Nov 7, 2018

I’ve been having a problem with my RAV 4 brake system for some weeks now, and I’m out of ideas on how to solve it. It’s a 2007 Sports model, from Japan. The lights I’m seeing are ABS, VSC, and BRAKE, and the codes are C1223, C1249, and C1380.

What happens is this: I get in, and start up, and the lights aren’t there. If I tap the brakes, the lights don’t come up either, but if I keep my foot on the brakes for more than 5 seconds, the lights come on, and stay on.

Whenever the lights come up, the idle speed of the engine increases.I’ve also observed that the center mount brake lamp is dim or flickers when the brake is applied. The two main brake lamps are working normally.

Based on that observation and the codes, I deduced that the problem must be that third brake lamp. I didn’t think it could be the stop light switch or relay, since the other brake lamps are working properly. I installed a new center mount brake lamp, but the lights are still there.

I then moved on to the stop light switch. I read the manual and tried measuring the resistance of the switch (pins #1 and #2 ). From what I understand, it appears that the adjuster part must be replaced if the stop light switch is removed and reinstalled. So I struggled to measure the resistance of the switch when it was still installed (obviously with the connector removed). I managed to get two readings, high resistance when the brake pedal isn’t depressed (good), but 2-3 ohms when the pedal is pressed (not good, should be less than 1 ohm). However, because of how tight that space was, I’m not sure if I made contact with the pins properly, or even with the right pins.

Strangely enough, after doing this measurement, the lights didn’t show up on the instrument cluster for about 15 minutes into my next drive, but they eventually reappeared. I’m skeptical about replacing the switch, because I’m thinking that if the switch was really bad, then it would have affected all the brake lamps. Similarly so with the stop light relay.

If it helps, I switched my reverse lights to LEDs, but I really don’t see how this conversion would’ve caused this. Any ideas?

Cutlass92 · Nov 7, 2018

I take it that since you have a mutimeter that you understand what ohms are, so the short answer is yes.

unit00seven · Nov 7, 2018

Yes, I'd say I have a fairly good understanding of what ohms are.

I am curious though, how is it possible that the apparently faulty switch does not affect the other brake lamps? (Interested in the long answer)

Dr. Dyno · Nov 7, 2018

Is there any kind of a taillight converter on the car? My dash lights went crazy when I accidentally left the converter ground wire disconnected.

And BTW I only use ohms for parts disconnected from a car. Voltage checks, particularly those with a 12V test light are much more conclusive on the vehicle.

unit00seven · Nov 7, 2018

Nope, no taillight converters on the vehicle. The only two things I did at the rear of the vehicle are: change the 2 reverse lamps to LEDs, and replaced the center mount stop lamp after the dash lights started appearing.

Are you suggesting that I repeat the measurement, keeping the switch installed in the vehicle, but instead measure the voltage across the switch contacts?

Cutlass92 · Nov 7, 2018

The left and right taillights go from the switch to a relay to the lights, the HIMSL HIgh Mount Stop Light goes to the ecm and because it has a triple flash then solid. So an out of range signal will cause the bcm to miss interpret the signal.

unit00seven · Nov 8, 2018

Okay then, interesting. Did not know this.

It would make sense then, that only the center mount is affected. I am guessing that you know it's not the ECM/BCM based on the codes that were generated.

Also, how did you discover this? Do you have the wiring diagrams or something of the sort?

Cutlass92 · Nov 8, 2018

Download this https://www.scribd.com/document/343938959/TOYOTA-Manual-Esquemas-Electricos-Toyota-Rav-4-2007

Salsaman06 · Nov 8, 2018

Would it be possible to post this somewhere where we can download without having to sign up for a trial service and having to provide a credit card?

Cutlass92 · Nov 8, 2018

I don't have it. I just went through it on the site.

Dr. Dyno · Nov 8, 2018

As I recall I got similar codes when my taillight converter ground was disconnected. The ABS malfunction one was pretty scary. And I do recall clearing the codes and shutting off the dash lights only to not have them come back with some combination of turning the parking/headlights on and hitting the brake pedal.

Apparently the missing ground allowed the two circuits to interfere with each other. If that's your case the problem is you can run all the continuity & voltage checks you want and everything will test good. It gets mystifying enough to confound this EE. May be a missing ground on the center brake light. So my suggestion is to put everything back to stock and go from there.

unit00seven · Nov 9, 2018

This sounds like a valid idea, since the pair of brake lamps have a different grounding point than the center mount lamp, based on the wiring diagrams.

But I did some more testing earlier tonight. I made some new observations:

1) The very first time the brake pedal is depressed after getting into the vehicle, all the lights are working perfectly fine. Bright, with no flickering.

2) Subsequent depression of the brake, and all three lights are significantly dimmer than usual (that is, the center mount, and 2 main brake lamps).

3) The center mount flickers a lot, and sometimes flashes once, but brightly (close to normal brightness), when the pedal is released.

4) The 2 main brake lamps have a very slight flicker to them, but I had to look very closely to see this.

5) With the pedal released, and the parking lights on, the 2 main brake lights are illuminated normally, with no flickering.

I feel as if the problem has gotten worse over time, since I don't recall seeing the 2 main brake lamps flickering. In any case, I think these are pointing to the stop lamp switch or BRK Relay being the problem, based on what I understand from the wiring diagrams.

What do you think?

Dr. Dyno · Nov 9, 2018

I agree most likely stop lamp switch or BRK Relay. Usually you can swap the relay with another to test it.
What I'd do is connect a 12V test light to the output wire of the switch and see if it mirrors the action of the lights themselves.

unit00seven · Nov 25, 2018

Okay, so I got the switch yesterday, and installed it today.

I haven't had a chance to go for a drive yet, but so far, all three brake lights are showing brightly, with no flickering. I believe that this most likely would mean the problem has been solved.

I'll watch it throughout the week, and report back. But again, most likely, problem solved!

Thanks for all the help.

unit00seven · Nov 30, 2018

Just confirming that the problem has indeed been solved. No dash lights illuminated over the past 4 days of driving.

Could stop light switch assembly affect center mount brake lamp only?

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