Mechanics or engineers explain this

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Hi all. As an emission Inspector the majority of vehicles that come in get driven on a dyne i.e on rollers to simulate driving. Now my question is this- Most two-wheel drive vehicles can be driven on a two-wheel drive dyne , EXCEPT several years of Toyota Avalons, one or two years of Camry, 2000 and newer Dodge Durango, mid 90's Lincoln Towncar, certain Toyota 4Runners with 4 wheel drive selector, and a few E series and S Class Mercedes Benz's. There is a sticker that reads something to the effect "This vehicle must be driven on an all-wheel-drive dyne or transmission damage may occur." 99.9% of the front or rear wheel drive vehicles don't have an issue. Its a few odd vehicles that nobody seems to know why they are this way. Anyone?
 
Maybe it has to do with the abs/traction control systems? It sees the front or rear wheels spinning but not the other and tries to correct the slippage? I'm not sure, just guessing here.
 
Zrxkawboy no many of these vehicles like the Toyota Avalon don't even have an awd setup. The Avalon is strictly front wheel drive. I had a 2006 Mercedes S500 rear wheel drive come in with no front driveshaft or awd components. It wouldn't go faster than 35 mph with traction control turned off or on. But driven on an awd dyne no Issue. It seems like it's random vehicles from various makes that do this, but not across the entire vehicle or manufacturer line.
 
On my Grand Marquis, they always tell me they have to turn off the ABS to run the test and that the brake light will be on for a short time, but will go out. They are right, it always goes off within a couple of miles.
 
In Ontario when we used to do the actual tail pipe sniffing test for our emission testing program we used to test these vehicles at idle only. Then it went to OBD-II testing emission monitors only. Now the program is scrapped all together for passenger vehicles.
 
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Traction control grabs the brake of the spinning wheel. I would assume that on an Avalon it grabs too much brake, based on a rear ABS reading of zero, which could lead to brake overheating and car damage.
 
ALL a big WASTE OF MONEY as the state of Minnesota found out. We spent 100 million dollars ++ on environmental auto testing sites through out the state back in the 90's and after 5 years shut them all down because they caught so little polluters it was A TOTAL WASTE OF MONEY. And for some un-Godly reason our left wing nut job progressives were "pragmatic" about [censored] everyone's money away on a stupid program that was bleeding money away from tax payers that made no sense and they had paperwork backing that outcome. It surprised me for once "emotional feel good thought laws" actually were crushed and sanity won the day. Man is that a rarity in progressive Maxist states.
 
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Originally Posted by slacktide_bitog
I thought they just did the computer test now
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That's what they have here, only older vehicles (pre-OBDII) are run on a dyno. I believe there is a visual inspection done also. My friend works at a quick-lube place that also does emissions, and with the number of vehicles that fail I don't think it is a waste of money at all. That particular shop is located in a lower income area with lots of cars that come up with VIN issues in addition to not passing emissions, having hacked off converters, etc. Many of the cars he sees shouldn't even be allowed on the road, but we don't have inspections here.
 
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