The check engine light is one warning most drivers dread. In many counties, it means a vehicle may not pass OBDII-based emissions testing, and you typically need a valid emissions test to register a vehicle in clean air areas. While all manner of issues from failed catalytic converters to a loose gas cap can cause the check engine light to glow, there’s a relatively recent annoying potential culprit to keep an eye on — a bad set of active grille flaps.
Technically, these aren’t usually in the plastic grille you see, but instead are a separate plastic grille just behind the main unit. So, how do these active grille shutters work, why would a malfunction trigger a check engine light, and how widespread are issues with these fancy pieces of plastic? Let’s dive into it, starting with that first question.
Over the past 90 years or so, automakers have grown more and more eager to cut drag in their new models. From the Chrysler Airflow to the super-slippery Lucid Air, a huge component of efficiency is being able to cut through the air cleanly with as little resistance as practical. Drag is the reason why some cars hit their top speeds long before they run out of gearing or into a limiter. Drag is also the reason why some pickup trucks come with goofy front air dams. Lower the drag, increase economy, and theoretically, everyone wins. The engine bay of a car is one turbulent area, so by blocking off the grille under certain conditions, a vehicle should become more aerodynamic.
While different automakers use different logic for their active grille shutters, on combustion-powered vehicles, the operating principles usually work a bit like how Nissan programmed its active grille shutters to operate. As per the Japanese automaker:
The active grille shutter is fully open when the vehicle stops or the ignition switch is turned OFF. The ECM operates the shutter to the closed position in order to perform shutter initial position learning when the ignition switch is turned ON. At the end of the initial position learning, the ECM operates the shutter to the open position until the vehicle speed reaches approximately 14 MPH. (The initial position learning is performed every time the ignition switch is turned OFF → ON.) While driving, after the initial position learning ends, the ECM operates the active grille shutter to the closed position when the vehicle reaches a specified speed for the first time. The ECM operates the shutter to the closed position when all the conditions of the active grille shutter are met: vehicle speed (approximately 19-88 MPH), engine coolant temperature (approximately less than 203°F), engine oil temperature (approximately less than 284°F), CVT fluid temperature (approximately 275°F), cooling fan ON and refrigerant pressure at 1.18 MPa or more. If the vehicle is driven at a high speed, the ECM operates the shutter to the open position when the vehicle reaches the specified speed of approximately 88 MPH in order to prevent the shutter from closing due to wind resistance. When the vehicle speed is reduced below the specified speed of 88 MPH, the ECM calibrates the active grille shutter to the closed position and then to the open position when the vehicle speed is less than 14 MPH.
When a vehicle’s switched on, cycling usually occurs to ensure that the active grille shutters still work. At extremely low speeds with airflow through the radiator being largely limited by what the cooling fans can push or pull, these active flaps stay open to prevent overheating. However, once a vehicle with active grille shutters starts moving and all fluid temperatures seem fine, the flaps close to smooth out the front end and improve the vehicle’s aerodynamics. If temperatures or speeds get too high, the grille flaps then open again to promote airflow and prevent themselves from being stuck. Makes sense, right?
So, why would these shutters set off a check engine light if they stop working? Because active grille shutters affect vehicle aerodynamics, they are considered pieces of emissions equipment. The EPA currently offers Corporate Average Fuel Economy credits if active grille shutters provide a reduction in drag, so all manner of automakers from McLaren to Subaru are hopping on the bandwagon. In theory, these moveable plastic grilles are great, helping engines warm up quicker and aiding in the pursuit of aerodynamic efficiency. However, if moving plastic parts on the front of a vehicle sounds like a recipe for problems, your intuition isn’t exactly wrong.
What can cause these active grille shutters to malfunction? Well, the actuator could pack up, the wiring could develop a fault, or, as Nissan puts it in a technical training article, obstructions may occur.
Service Tip: Debris or snow caught in the shutters may prevent proper system operation.
Ah, yes, snow. You know, the natural phenomenon that tens of millions of North Americans experience seasonally. This is like when heavy rain overwhelms forward-facing RADAR units, except “automatic emergency braking unavailable” doesn’t trigger a freaking check engine light.
Even worse, issues with these active grille shutters happen all the time. The active grille shutters on many early 2017 BMW 7 Series and 5 Series models are crappy enough that BMW has extended warranty coverage on the components for 10 years or 120,000 miles, as per technical service bulletin SI B01 01 19, and Nissan has a whole set of instructions for the Versa Note’s active grille shutters that I mentioned earlier. Oh, and that’s before we dig into owners’ forums, where drivers across multiple makes and models report having problems with their grille flaps.
Maybe it’s just me, but this forum post from a 2022 GMC Sierra owner reporting active grille shutter problems with just 800 miles on the clock doesn’t seem particularly confidence inspiring. It’s certainly not the only forum post about active grille shutter issues on GM trucks, with trouble codes being reported over two generations of full-size pickup trucks.
What about across town at Ford? Well, F-150 owners are also reporting active grille shutter problems. The above forum post comes from the owner of a 2019 F-150 with the 3.5-liter Ecoboost V6, and several F-150 diesel owners in the same thread report similar issues. Mind you, the F-150 isn’t the only Ford product in which owners are reporting active grille shutter failures. Just check out this post from a 2016 Explorer owner below.
Alright, so we know that BMW’s had issues with active grille shutters, Nissan has published an entire diagnostic tree, and domestic vehicle owners report issues, but what about owners of Japanese cars? Well, previous-generation Honda CR-V owners are reporting fairly widespread issues with grille shutters, with the forum post below being merely one of many scattered across CR-V owners forums.
As for Toyotas, grille shutters can fail on those things too. The Camry Hybrid is a model for robustness, the de facto taxicab from Sydney, Australia to Sydney, Nova Scotia. We’re talking about a vehicle that’s built to last, so any unusual failures like this owner’s active grille shutters are worth cocking an eyebrow at.
Adding insult to injury, paying to replace these active grille shutter units can potentially wipe out fuel economy savings. Directly from Nissan, the active grille shutter assembly for a 2017 to 2019 Versa Note carries a suggested retail price of $363.64. That’s just the part, no labor. The Explorer owner several posts up the page claims a repair quote of more than a grand, and shutters for a half-ton Silverado go for $324.99 at Autozone.
While cutting drag with active grille flaps can gain regulatory credits, promote quicker engine warm-up, and save drivers some cash at the pumps, replacing active grille shutters can be a pain. In a climate as varies as North America’s, the promotion of such a technology seems a bit like theory trying to assert superiority over practice, with predictable results. As vehicles with active grille shutters age past a manufacturer’s parts support period, one can reasonably assume that bad active grille shutters may send vehicles to the junkyard if good replacements dry up. We’re really looking at unnecessary complexity for the sake of regulatory kudos, a neat but flawed idea that’s made it under the hood of many vehicles.
(Photo credits: EPA, Nissan, GMC AT4 Forum, F-150 Forum, Explorer Forum, CR-V Owners’ Club, ToyotaNation)
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Ah yes, Japanese cars as opposed to Nissan. ಠ_à²
OK, hear me out and keep in mind I used to be an aerodynamics boy with a focus on icing. That means I’m only talking out of my ass at like 40%.
How about placing those shutters behind the radiator? You can throttle air flow downstream of a current. The resulting upstream aero would be a little messier, but your fragile flaps would be protected from direct mechanical damage and be in a warm environment, protecting it from snow, icing and such nastiness.
Otherwise, we fixed this issues on aero turbines using hot air running inside the Inlet Guide Vanes (which are kind of the same idea), but that seems unrealistic from a cost perspective.
Would have been nice to have noted in the article examples of the mpg gains these devices provide. While I’ll bet the average owner wouldn’t be able to track them tank to tank, a 1 or 2% gain could be meaningful over the lifetime of a vehicle if enough are produced…
but then I lapse back into curmudgeonhood grumbling about ‘fiddly plastic bits’ and ‘more silly controls to go haywire’ and start daydreaming of Model T’s again
These must be great for automakers but bad for the environment, a CEL will cause a 2nd-4th owner to junk a car prematurely, which will eventually lead to another car being purchased. The. 04mpg’s these save Will not offset the greater repair costs, insurance cost or initial cost. Can someone please stand up to the EPA and tell them that they can stop raising the MPG requirement because the “unintended” effects are hurting everyone.
How fast Doc???
We could have had flux capacitors and 1.21GW of power at 88mph to take us anywhen we want. Alas, today we end up with these fragile, flappy pieces of plastic to save a few drops of dino juice
The shutters didn’t fail in our Pacifica as much as when CarMax reconditioned the van prior to purchase, they took the front bumper off, removed the shutters to do some touch up work on the bumper, then popped the shutters back in and put the bumper back on without reinstalling any of the fasteners. The only thing holding it in place until I took the bumper off a couple weeks ago to snap the grill back in place (which popped out because said fasteners were missing) was it being wedged between the bumper cover and the impact bar. No idea if the shutters opened or closed during this period of nearly six years, but we never got a CEL for it.
Active grills reminds me of the air filter intake to my ’67 VW squareback. There is a flap that allows cold air from outside or warm air from the engine bay.
Wait until you find out that a lot of modern cars have screens instead of physical gauges.
Or, even better, motorised HVAC vents!
I don’t mind screens so much over physical gauges. From a reliability standpoint, there’s less moving parts than physical gauges. And screens themselves are pretty reliable at this point with our tech.
Motorized HVAC vents… not sure I can get behind that. But probably a fun feature when before it breaks.
Noted. Check next car to see if it has shutters, as it seems like just one more thing that would cause a failure in my state’s OBD inspection. No thanks!
Man, this article has certainly caused a flap.
Do the popup aero things on the back of Porsches trigger CELs when they don’t work?
Wouldn’t a bimetallic thermostat heated by the coolant hooked by a lever to operate the slats be simpler and more reliable? I think that’s 1920s technology,
Well that IS how the thermostat works. It just selectively blocks water instead of air.
Another possibility is slats that are activated mechanically by speed either via airflow or tire rotation.
Well the thermostat that is in the coolant line gets called a thermostat, but the automatic choke and the heat riser on carbureted cars are also actuated by a device known as a thermostat. Old Rolls Royce and Packards had the most conspicuous ones.
It’s sort of like how there are many valves in an automobile, but people tend to think of the ones in the engine not the ones in the heater.
My point is that computer controlling the shutters seems needlessly roundabout.
Hard to say, mechanical control might work fine 70-80% of the time but if electronic control can work better with similar reliability and cost I’d do that. A lot of folks were hesitant to move from mechanical points to electronic ignition but I don’t think anyone really want to go back now.
When I first heard about active grille shutters, my first thought went to snow and ice jamming the mechanism. All of us here in the North have experienced freezing rain making it a pain to get your door open or iced windows that won’t open. I imagine that plastic is going to get brittle and more prone to breaking in the cold too.
Oh the joys of modern tech. These have been around for ages, the mechanical bits cost probably 5$/€/£ to make and the sensors can be defeated by coding, so probably won´t be reason to scrap an otherwise working car.
Unfortunately my central european wundermachine lacks this wonderful feature due to VW group cost cutting. Yet, it really makes sense to close the radiator in the arctic environment. So what to do? Pay 60€ for a piece of plastic and some fancy clips? Hell no, black ducktape in the lower grille works just as well, does not stand out, is easy to rip out in the spring, and the roll lasts for a decade. Except for the adhesive, but… And besides the engine warming faster, it protects the radiator and ac gubbins from stone chips etc.
TLDR: Snowman tape over speedholes. Car warm fast.
I always used a piece of cardboard between the grille and radiator on my 2000 Ranger. It had the most overpowered cooling system I’ve ever seen, but that meant that it sometimes struggled to stay at operating temperature in winter during easy driving. Blocking half of the radiator fixed it.
Some SAABs prior to the introduction of the “long nose” 95 and 96 are equipped with a roller shade for blocking the grille during cold weather:
https://www.classicargarage.com/assets/images/1/saab-93-two-stroke-15-87e41e11.jpg
The deployment mechanism is identified by noting the small pulley above the grille, through which a cable passes. The other end of the cable is joined to a chain, visible along the left side of the engine compartment, which goes through the firewall so that the shade can be held in any position by catching one of its links in the narrow part of a keyhole-shaped aperture.
Later models don’t have anything this convenient but the company did offer a set of detachable covers for blocking part or all of the grille from the outside.
(If you’re wondering about the weird-shaped thing partially blocking the lower right portion of the grille, it’s meant to help keep water from splashing through the grille and onto/into the distributor.)
Well don’t trust Stellantis, nee FCA as I had a low mileage 2020 Jeep Cherokee that I had purchased off lease with less than 6000 miles on it, but in less than 1 year and only 12000 something miles the active grille shutter failed open, but set the CEL despite not affecting the vehicle operation. However because they don’t classify the active grille shutter under an emissions component warranty despite it triggering the CEL and in certain states means it’s no longer registerable until it’s fixed they refused to warranty it, and the scumbag dealer charged a diagnostic fee to tell me what I already knew which was they died.
Needless to say I dumped it to the highest bidder and bought something more efficient to commute in at the time.
Interestingly, my ’23 Volvo xc60 offers these on pretty much every market EXCEPT for US vehicles. Canada, Europe, ociana all get them. But not in the good ol US of A. Anticdotically, they dramatically improve MPG in cold months as the VEA engines will run cold without them.
I can confirm this on your 2020 Transit Connect. This bugged the hell out of us. So instead of taking it to the dealership, I actually remove 10 of 14 of the slats. Just pried them off and pulled them through the grille. Ironically I posted this info on the ecomodder site and they all discredited my findings. But while this system was closed, the van drove like a brick.. Removing these slats has allowed for more air flow and we’re getting better fuel economy.. One other thing I discovered while at the transit forums, Owners were thinking the van didn’t have a trans cooler.. but removing the slats proved differently. Bam top of the radiator was the trans cooler. So no wonder the trans and engine was running hot, Cause the system is flawed. I left 4 slats just so these system could think all the other slats are working correctly. ZERO error code and the van is running smoother and more fuel efficiently.
I’ll be the heretic who defends these things. Living in a cold climate, grille shutters make a huge difference in warm-up times. They are also (theoretically) seamless in operation. Currently, on my older vehicles we have to put vinyl “winter fronts” to cover the grille. But if I am towing heavy, I have to take it off. Drivng down to Anchorage where it is 40 degrees warmer? Stop and take it off, and then reverse on the way home. I’ve never disabled my shutters to see what impact they have on fuel economy, but I know that my modern vehicles with EGR, intelligent cooling circuits and grille shutters only suffer about a 20% hit in the middle of winter versus almost 35% for my vehicles that are old-school.
I know I am just one data point, but the shutters on my F-150 diesel have been flawless as I push the 100,000 mile mark.
My Cruze has them. First thing I did was rip off the front bumper and install pet screen in front of those shutters. It’s saved all manner of debris from entry. No issues with overheating either.
They don’t have to be unreliable – I have them on my ’87 928, and while they have been serviced (when I got the car they were “sticky”) they haven’t been replaced.
Back in the day, dumb jackasses would place a piece of cardboard- a flattened box or beer case- in front of the radiator in winter, claiming it would make the engine warm up faster.
They were right, but… this is just as stupid. Adding a lot of fiddly fussiness just to gain a tenth of an MPG!
In Canada that’s known as the Saskatchewan Thermostat. I had to install one once on a ’78 GMC Vandura while making the chilly trip east to west across N. Dakota. They really are effective, we were freezing our asses off before, and after we were just freezing our fingers off. The trick is to remember to take it off before summer rolls around.
Grew up in Sask. Blocking the opening using cardboard or carpet was common back in the day. Temps of -35 – -50 C (roughly the same ranges in F) were not uncommon. Cars warmed up and stayed warm.
Yup, I worked tow truck in Banff in -40. Brought a lot of frozen vehicles into the shop for a warm up!
It’s a dry cold, just layer up. I live in eastern ontario. Not as cold temperature wise, but the humidity cuts through you.
I knew a guy from Fairbanks who lived here in Chicago and said it was colder here.
What?
Yup, because “in Fairbanks it’s a dry cold.”
I remember regularly taking the bus up to Sunshine, before the lift was put in (terrifying). We used to ski as long as the mountain was open. There were many times I came close to freezing my feet and hands. Years later got my instructors certification. Standing for hours in the cold was much worse.
School buses around here cover their huge grill because of winter temperatures and you dont want kids to complain about the cold lol same concept with a piece of cardboard, it really works.
I do this to my Prius, but it’s not (just) for MPG. That small engine cools off crazy fast when you’re coasting down a long hill in 0 degree F weather. It warms up much faster and stays warm better if I block airflow through the front grille. I watch components temp like a hawk with Torque and until it gets into the upper 50s or 60s everything stays cooler than it does on a hot summer day.
As one of those “dumb jackasses” I needed to cover half of my radiator when the temp dropped below 25F or so. If I didn’t, my 2000 Ranger wouldn’t be able to stay at operating temperature during light highway driving. It still had enough cooling to drive in hills with a small trailer, too. I always watched the coolant temp gauge, but never had the temp go above normal operating range. The truck had far more radiator than it really needed, which was great in Texas and Arizona summers, but meant that it would barely stay warm in Northeast winters.
If my calculations are correct, when this baby hits eighty-eight miles per hour… you’re gonna see some serious shit.
Yeah, that’s the 1st thing I thought of and surprised he didn’t make a joke
there’s gonna be whole ass “how to delete your active grill shutters” threads on enthusiast VR forums or whatever exists in the completely enshittified future.
Or at least how to trick the ECU into thinking they are working to shut off the CEL so the 3rd owner can register it and legally drive to work.
Happened to a family member on a new X5. A rock got stuck in the active grille, causing the engine to go into limp mode to prevent overheating. Dealer removed the rock and things returned to normal. Frustrating and annoying, but credit to the dealer for handing it without issue.
That’s just so fragile, so silly.
Motors go bad on the Q7’s. Audi has extended coverage I think. And yeah, it doesn’t just throw a MIL. It gets angry.