By on July 27, 2018

Isuzu Ascender Rear, Image: GM

Chris writes:

2006 Isuzu Ascender: the reverse lights are on while driving forward, in drive. I got pulled over for this. Anybody have an idea why they stay on when in drive? How I can troubleshoot this issue?

Thanks for your time.

Sajeev answers:

Usually my gut reaction is what I elucidate in a Piston Slap reply, but the obvious reverse switch for your vehicle doesn’t exist. Damn my incorrect gut!

But that’s fine, parts get consolidated as features integrate: no more individual switches for neutral safety and reversing, new vehicles put it all in a single Parking/Neutral Position and Backup Lamp Switch. Aside from the obvious need to check the wiring for damage/hackery, either the Body Control Module (BCM) or that switch are to blame.  Check out RayVoy’s reply to this thread: does your gear indicator in the gauge cluster also read incorrectly?

So it’s your call, either you replace the switch or test the BCM to ensure buying the switch is the correct repair.

Judging by the hits on Google for failing switches, by its affordability (under $60, probably less than the BCM test at any shop) and by my experience with it being a wear item (changed my 1995 Mark VIII when it was 16 years old), you would be forgiven for replacing it prophylacticallyand hoping for the best!

Off to you, Best and Brightest.

[Image: GM]

Send your queries to [email protected] Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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29 Comments on “Piston Slap: The Backwards Ascent?...”


  • avatar
    Chris Tonn

    My suggestion, as a fellow GMT360 owner:

    See if the truck can handle a float test.

  • avatar
    salmonmigration

    Unplug the light bulbs. GM reverse lights stay on after you lock the car and walk away, which makes people falsely think you’re backing out of the spot.

    You’d be doing the public a service.

    • 0 avatar
      Kyree S. Williams

      I find that feature annoying on my ’16 Cruze. But it seems like people ignore it. Maybe they’ve seen it enough. I’ve never had someone wait for a spot my car was occupying while the so-called perimeter lighting was activated.

      • 0 avatar
        Rnaboz

        Yes, it is a pain and an annoyance. I ended up filing a complaint with NTSA after seeing three kids playing behind their mom’s GMC with the reverse lights on. If their neighbors own a Toyota, they’re toast.

        I now ignore GM vehicles with the reverse lights on.

      • 0 avatar
        JohnTaurus

        Kyree, I think you can program it to not do that.

        One of GM’s worst ideas. I mean, I get why they did it, but its a horrible solution to a problem nobody complained about. If they wanted to shed light on the rear of the vehicle, why not something similar to a cargo lamp combined with a CHSML (as on the cab of a pickup) on the back? At least it wouldn’t be mistaken for a car that just engaged reverse and let off the brake pedal.

    • 0 avatar
      87 Morgan

      I was going to post the same answer. Remove the light bulbs. Problem solved.

    • 0 avatar
      nramacciato

      How is this even relevant to the writer’s issue?

    • 0 avatar
      Instant_Karma

      That feature almost got my dad shot by a cop. As an early adopter of the 2007 “new body style” Silverado, he was pulled over and shut the truck off, cop sees the backup lights illuminated and pulls his pistol then yells at him and tells him to shut the truck off. He had to hold his keys out the window to convince the officer that it was indeed off. Some scary stuff for both of them.

  • avatar
    pwrwrench

    Has it been to a body shop? They are well known for “fixing” wiring to light assemblies.

  • avatar
    MrGreenMan

    On my ’06 Malibu, I had similar electrical craziness. Someone had tightened something too much on a recall, which caused the BCM to develop a flex in it. This then caused the voltage to swing wildly at inappropriate times.

    I believe I had to replace that part twice; the second time was chipmunks.

  • avatar
    Kyree S. Williams

    I see that BCM failure a lot. Specifically, I see it on Pontiac G6s, wherein the brake lights will be illuminated while the car is traveling down the highway, but turn off as soon as the driver depresses the brake. I have also seen it on the Kappa (Solstice, Sky) and early Theta (Equinox, XL7, Torrent) cars. It seems to have been rectified when they switched to the Global A electrical architecture…which started with the 2010 Camaro, 9-5, Equinox, Terrain, and SRX.

    • 0 avatar
      JohnTaurus

      The FWD minivans and Express/Savanna were also super bad about that. The brake lamps on a Venture look like cheap Christmas lights flashing when someone unfortunate enough to be driving it has the audacity to use a turn signal or brake.

  • avatar
    Shortest Circuit

    W210 and later E-Class Mercs don’t have neither a brake nor a reversing light switch. The lights are triggered by the ABS/TCM computer sending a CAN command to the rear SAM module. Now for safety reasons there IS a brake switch but that is for the ECM to limit power if someone decides to depress the throttle and the brake together.
    In short, pretty much anything (bar a Mahindra or Lada) since ’93 – you will need a computer to fix sh1t like this.

  • avatar
    dividebytube

    This used to be a fairly common sight here in Michigan – I was told, back then, that it was caused by people slamming between Reverse and Drive, often done in an attempt to get a car unstuck.

  • avatar
    Zackman

    This proved that early 2000s GM vehicles, except my old 2004 Impala were pretty faulty vehicles in the electronics department. As far as the Trailblazer and its many cousins go, electrical problems are the norm, as our daughter has found out with her 2007 Trailblazer. Overall it has been a great car, but the electrical gremlins tarnish the ownership experience.

    Sell or trade it ASAP.

  • avatar
    CobraJet

    When I was a teenager, the backup lamp switch failed on my 1966 Mercury Comet. I wired the lamp circuit to a toggle switch that I mounted under the dash. If I wanted backup lamps, I just flipped the switch. It was sometimes handy when being tailgated. I would flip the switch on and off. This usually made the car behind back off, not being able to figure out what was happening.

    • 0 avatar
      RHD

      Great idea. Anything that will get a tailgater to back off is useful.
      Requesting additional suggestions from the B&B would make a great article.

    • 0 avatar
      RHD

      Great idea. Anything that will get a tailgater to back off is useful.
      Requesting additional suggestions from the B&B would make a great article.

      • 0 avatar
        JohnTaurus

        Call and make sure your insurance is up to date, then pull up on the hand brake.

        If seeing my brake lights don’t give you the hint, perhaps rapid deceleration without brake lamps will give you a clue that what you’re doing is wrong.

        Kids, don’t try this at home. Its a joke.

        (But, it works.)

      • 0 avatar
        Erikstrawn

        I met a trucker once who swore by peanut M&Ms. He said if he tossed one out his cab, the wind down the side of the trailer would accelerate it enough that it could crack a windshield.

  • avatar
    turbo_awd

    In my childhood, two countries and a continent ago, in a simpler time.. Around 1977-1978, our Renault R16-TS (maybe a 1970? or a 68?) had needed a new bulb of some kind – I forget which, maybe rear brake / turn signal? And apparently, the wrong size / type had been installed, and afterwards, when depressing the brakes, the main headlights would come on (or possibly reverse lights).

    Installing the correct bulb fixed it.

  • avatar
    cimarron typeR

    I remember on our old 1980 Accord 5mt that my brother and I drove in HS in the 90s (tan over tan btw) developed a problem where the brake lights would stay on permanently while we were at a regional tennis tournament with 2 other buddies.
    We rigged up a system with 2 tennis racket bag straps that the backseat passenger would tug on the whole drive home. It ended up being a worn out solenoid type switch on the brake pedal when we took it to the shop.Fun times.

  • avatar
    Vulpine

    Once a very common problem with column-mounted automatic levers. Switch would slip out of position and have the reverse lamps on while driving forward. I used to see this a lot in the 60s vintage cars, especially.


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