2001 V70 2.4T Brake light problems

[prwood]

A few weeks ago, I started getting a "check brake light" warning on my 2001 V70. It would sometimes come on when I hit the brakes, but other times not. Eventually it got to the point where the warning always came on when I hit the brakes. I checked the brake lights, and the light that was not coming on was the left side brake light. The right side and the top center brake lights came on normally.

My first thought was the bulb - it didn't look burned out, but I replaced it anyway. Still no left brake light when braking.

My second thought was that maybe there was an issue with the brake light socket, so I swapped the sockets (with bulbs) between the left and right sides, and the 'no brake light' problem moved from the left to the right side. Seemed like a pretty solid case for the socket going bad, so I bought a new socket, and swapped out the right side socket for the new one, put the bulb back in, and the right side bulb still refused to light.

Hmm.

I pulled both of the sockets out, cleaned the contacts on both the socket and the tail lamp assembly, and reinstalled. For the initial press of the brake pedal, all three brake lights came on. However, as soon as I let go, the next press of the brake pedal resulted in NEITHER of the side brake lights coming on.

I did some research, and saw that a bad brake light relay or fuse was a possibility. I swapped the brake light fuse, still no brake lights. I swapped the brake light relay (which is a double relay shared with the rear fog lamp), with the reverse light relay, still no brake lights.

Any suggestions for what to try next?

[jonesg]

many of the threads dealing with this that I've read turn out to be in the harness where it passes thru the hinge area.

[br0dy519]

Common issue on hatchbacks of all brands is any sort of wiring in the area jonesg is talking about. Happened on a ford focus to me. Simply peel the boot back and inspect the wires beneath the loom. I'm sure you'll find a break in there.

Just be glad you can still shift between P,R,N,D. Might be worth looking into shift interlock overrides in the car in case you get stuck before fixing it. Often if the brake switch doesnt fully make or see the lights coming on it won't allow you to shift.

[prwood]

Are we talking about a wiring harness going through the tailgate hinges? If so, why would that affect the side brake lights which aren't on the tailgate? The brake light at the top center of the tailgate isn't affected.

[br0dy519]

crap, didnt mean to steer you wrong. Doubtful its related to that wiring then

[jonesg]

Are we talking about a wiring harness going through the tailgate hinges? If so, why would that affect the side brake lights which aren't on the tailgate? The brake light at the top center of the tailgate isn't affected.

I would try a test light probe, see if you can detect voltage at the socket with brake pedal blocked and follow it back along the wire.
Robert shows how to gain access to the wiring source.


also,

[prwood]

I did some testing with the multimeter on the brake light contacts in the tail light assembly:

With the car running and lights turned on:
- Left 1.1 mV
- Right 1.7 mV

With the car running and lights turned on but brake lights not activated:
- Left 3.2 mV
- Right 6.1 mV

With the car running and brake pedal actuated:
- Left 13.3 V
- Right 13.4 V

I also measured ohms resistance across the brake light socket contacts with the bulbs installed, and got a reading of 0 ohms resistance each time.

One thing I haven't tested yet is the brake light shunt, RSH6 on this diagram:



I am also wondering if what I'm seeing is a possible sign of REM failure.

[volvolugnut]

My 2001 V70 has had multiple problems with "Bulb Failure Position Light". I believe the root cause is poor contact with the socket in the light housing. Sometimes I had bad bulbs and once I replaced the left light housing because the plastic tabs were broken and would not hold the socket in place. Slight wiggling of the socket may provide short term relief.
volvolugnut

[abscate]

I’ve had ongoing 18-24 month issues with my REM fuses oxidizing giving GEF…general electrical funk.

Try cleaning everything, scraping to shiny metal

[prwood]

Normally I don’t have problems with intermittent electrical issues… unfortunately, this one makes my car illegal to drive. Probably some contact cleaning is in my future.