Piston Slap: Putting the Brakes on Auto Start/Stop?
Hagerty Community member HelenC writes:
Sajeev, my question is how do you disable the stop/start feature on a Jeep Grand Cherokee? It would be a tremendous service to your readers if you explained how to do it on not only Jeep products but GM and Ford.
I know the car companies have not come up with such an iterative feature since they put those seat belt starter interlocks on cars back in 1974. However it was easy to disable by just cutting all the wires under the seat. This aggravation may be more complicated to find which wires to cut so all your help would be appreciated.
Sajeev answers:
Turns out I got this one wrong, as there are modules that defeat this system. But remember these can void your vehicle’s warranty, so let the buyer beware.
Before I reply, please permit me to weasel out of a proper answer. Because getting a representative vehicle from all manufacturers, performing the task (either manually or electronically) to verify for myself, and then subsequently getting banned from all media fleets would kinda tank (what’s left of) my career as an automotive journalist. I’m only kinda joking, as doing this on not-media fleet vehicles would also be too cost prohibitive. And with that out of the way…
Let me instead point you in the right direction to disable auto start/stop in your vehicle. And this “pointing” is more valuable over time, as vehicle systems change over time, but the people who work on them generally do not.
- Call or email ECU tuners (Ford, GM, Chrysler) to see if they can remove auto start/stop from their software. This is often possible, but only they will know as they have access to the software and the ability to do what you want.
- Ask a dealership’s service department if start/stop can be removed either with their software, or unplugging/bypassing a wiring harness. (I assume the answer will be no, but it never hurts to ask.)
- Find out who makes the start/stop starter unit in your application. (Denso is a well known brand in this space.) Once you know the brand you can see what inputs it takes from the rest of the car to operate. Maybe you can disable start/stop without destroying the rest of the starter.
My advice tries to cover all bases, but honestly, you only need the first option. An ECU tuner will know more than anyone else, as modern cars use multiplex wiring that ensures any physical modification will take out more things than just the start/stop feature.
I suspect a tuner can make the system default to “off” so you can hit the button and turn it on if you tire of getting 0 MPG in traffic. Problem is, the tuner’s work isn’t free. It will cost hundreds of dollars, but it’s worth it if you also load a tune that allows for more power (premium fuel sometimes required), eliminate the throttle/torque management software, and firm up the transmission shifts.
Almost all of my EFI-powered vehicles have been tuned by a professional in the aftermarket, and I recommend it for more reasons than just disabling a start/stop feature. But that should get you exactly what you need, no matter what make or model we are discussing.
(For the record, I have no problem with this feature in late model vehicles. Times have changed, its operation is relatively seamless, and eliminating periods of 0 MPG when stuck in suburban sprawl has financial and ecological merit.)
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I would like to thank everyone in the comments for filling in the HUGE gap I overlooked, as there are indeed modules one can guy to defeat the system. I think your comments deserve a Part II on this subject.
My ‘8 Vette, 2000 Cherokee and our 2013 Venza … We don’t need no stinking auto-starter…We just go without a 5 second lag at the lights or in an emergency situation! We don’t have to wait for the engine to think about starting!
I’m not pouring through all the comments here.
I just wanna say my only issue with start/stop is this:
What’s the highest point of wear for an engine? Specifically the main bearings and rod bearings?
Startup. Cause until you build oil pressure to glide on, that’s all bearings.
Now, not much of an issue for the few seconds it takes…until you’re repeating that process a hundred times in stop & go traffic on the daily. Now instead of seeing that moment a few times a day, it’s seeing it constantly.
How well does that bode for the longevity of the bottom end for those of us that want to own a vehicle long-term?
I suppose I’m unique. Though I love cars, I also love the outdoors. Mountain biking hiking, or just as fun as my old convertible 911. However, when I ride in the wilderness I know there’s certain places I can’t go or I’ll destroy what I love. I think this car lovers we need to realize their limits to what we should do. Excessive pollution with no gain is definitely one.
Toyota admits to 384,000 times before the starter will indicate it needs replaced.
Easily the stupidest thing ever added to the cost of a car. The idea for it was spawned in the head of a government bureaucrat…. A poli sci major with zero practical knowledge about anything…. Sheesh..
You’re also describing the politicians who think it’s a great idea.
They don’t think about long term consequences.
There was a Congresswoman a couple of years ago who suggested grounding the airlines, people would travel on a high speed rail network (at 1/3 the speed).
She was really talking it up until a Senator from Hawaii told her Railroads won’t work for getting to his state.
Forscan and jscan can do it. As for gm I’m not sure.
I have a 2019 cadilac xt5. The problem is that as I inch in the garage the car stops and when I am very close to the desired location, the car stops and sometimes I forget it stopped and I didn’t yet turn it off. i might get out of the car with it still running. I found the solution. Put the transmission into manual as I pull into the garage.
Why disable the feature in a computer car? It seems that the auto stop/start feature is a good gas saving measure, and will help keep ICE vehicles on the road.
*commuter
I hate the auto start stop systems. Thankfully I own no cars with it but my Dad’s car he just pushes the button to turn it off every time he gets in the car.
Grand Cherokee autostart stop stop.
Disconnect the battery status wire attached to the positive post on the battery.
Push button down to disengage auto start stop slip the end of a wire tie between the button and the housing,snip off about 1/16 above housing button will be in off position until wire tie is removed. I have been driving my Hyundai like this for over a year with no adverse effects. It is not a modification of any system, it’s legal,and won’t void warranty. To return to original, simply remove the wire tie with a pair of tweezers
On the start stop, my daughter has a Chrysler van. She can disable it from the dash or steering column.
I don’t own a vehicle with this lovely technology (so far) but I’m old enough to figure that if a car can start in gear that’s kind of dangerous? What if someone has drained the basepan and something tells the car to start with no oil in it? This is supposed to help the manufacturers meet CAFE standards? How much sooner do these starters burn up?
This is going to eat starter motors and cause major issues as vehicles age as well as it’s hard on the battery..Mazda (once again and as typical ) came up with a genius way to have stop start without eating startermotors …they have a special altanernator which brakes the engine while shutting it off THEN they inject and ignite fuel at the same time jump starting the engine without the startermotor …GENIUS IDEA so go buy a skyactive Mazda but steer clear of a diesel the look to be problematic