Keeping Flexible with New Electronics

What your technicians need to know about electronic controls on clean diesels and flex-fuel vehicles.

Flex fuel and clean diesel engines are helping to reduce emissions, noise and fuel costs for fleets, but that also means more things to worry about. New electronic controls are important parts of these new technologies, so your technicians need to be up to speed on how to troubleshoot and fix these systems.

Flexible fuel vehicles can run either on gasoline or blends of up to 85 percent ethanol and are very similar to regular gasoline-only vehicles, with only a few changes to the engine and fuel systems. These flex-fuel vehicles have been around for a few decades, and today there are dozens of different models to choose from.

GM Powertrain BioFuels manager Coleman Jones says fleet interest in flex fuel vehicles has picked up recently, as many fleets are calling for them in their statement of requirements. With these vehicles come some new controls that technicians need to understand, though.


One change is the sensors that make sure the ethanol-gasoline blend is appropriate. Jones says GM previously used a physical flex fuel sensor to measure fuel capacitance and composition, but introduced a “virtual” replacement in 2006.

“It uses the oxygen sensor and the fuel tank level sensor to calculate the fuel in the fuel tank and it also calculates the composition of the fuel you put into the fuel tank,” he says. “It’s what we call a rationality check—the technician can read what the vehicle thinks it’s burning and we have a tool that allows you to actually determine the ethanol content of the fuel sample if you pulled it out of the tank. One of your service procedures is to compare what your vehicle thinks it’s is burning versus what it is burning.”

Another potential issue for techs to be aware of is the disparity between the various mixtures of ethanol and gasoline, despite what may be advertised. Jones says fleet managers need to know exactly what they are putting in their vehicles.

“When we introduced this we assumed that the only fuel sold in the U.S. would be fuel that meets specifications for E85, and it turned out to be wrong,” he says. “(Misidentified fuel is) out there and we have to deal with it.”

To help mitigate the problem, GM released a software update last year for vehicles with older software, such as pick-ups and utility trucks.

“(Otherwise, if) you took one of these vehicles that has this older software and fueled it with E20 or E60, it would not compute, which doesn’t mean you would immediately set a (warning) code, but you might,” Jones says. “So there is a service action out there, so if the vehicle goes into the dealer for any reason, they’ll get the update. If you get a car coming in that shows a typically lean bank one or lean bank two code, you ask the driver if he’s been running E85 and then you might want to check to see if the fuel in the fuel tank matches what the controller thinks it’s burning. We don’t see it very often; we’re just being proactive. This is what you’re going to see in the future.”


For fleets without flex-fuel vehicles, Chicago-based Flex Fuel U.S. sells a “Flex Box” that allows gasoline-powered vehicles to run on E85. Their ethanol conversion system was recently certified by the EPA—the first such system to receive that status after more than two decades of attempts by the industry, says company president Mitch Sremac.

“Fleets are always concerned with insurance and OEM warranties, so they’ve never been willing to put a kit in a car because they weren’t street legal,” he says.

With federal laws mandating commercial fleets with more than 50 vehicles to have a certain percentage run on alternative fuels, Sremac hopes the certification gives his company a leg up on the competition.

“A lot of fleet people have been calling us and asking about the system,” Sremac says. “Because of that requirement, guys have gone out and spent money on LPG (liquefied petroleum gas) and CNG (compressed natural gas) kits. Well, LPG is a $5,000 conversion and CNG is about $8,000. Our kit you can have installed for about $1,200 and it doesn’t take up any space. You can run gasoline or ethanol, whatever you have.”

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