Why doesn’t EV mode work in the Jeep Wrangler 4xe when it gets cold outside?

Jeep Wrangler 4xe owners in cold climates are finding out they’ve really bought a “Summer-only hybrid.”

A big reason why Jeep Wrangler 4xe owners pay an almost $24,000 premium over a regular gas Wrangler is for its hybrid capabilities, particularly being able to drive up to 21-miles in electric-only mode.

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Unfortunately, many Wrangler 4xe owners are finding out, as soon as Winter arrives, their Wrangler 4xes decide outside conditions are too cold to operate in EV mode and force the engine to kick in, disabling electric only capabilities for several hours or hundreds of miles.

Without the electric motor to supplement the 2.0L turbo gas engine, owners in cold climes soon find their $54,000 Jeeps are now under-powered, achieving, at best, 20 MPG combined, before the 4xe’s ECU restores hybrid capabilities.

First, there are conditions that disable EV mode, including starting in cold ambient temperatures.

There’s also Fuel and Oil Refresh Mode (FORM) and, to prevent a Wrangler 4xe’s fuel and oil from becoming stale from sitting for too long due to repeated EV mode use, the 4XE’s ECU will disable EV mode when it determines certain criteria are met.

Generally, FORM disables when oil temperatures hit above 210F for at least 20 minutes but, in highly variable cold temperatures, that could take, as mentioned, several hundreds of miles or hours to achieve.

It doesn’t help most drivers don’t drive long enough for oil to stay that hot for that long, anyway.

And it’s not an unknown issue either, it’s spelled out in the Wrangler 4xe Hybrid Supplement issued to owners.

Wrangler 4xe owners should’ve done their due diligence and researched their PHEV’s capabilities in their particular climate before financing over $50,000.

But, like most car shoppers, they generally assume their car, PHEVs included, should operate as expected no matter the temperature and aren’t properly informed by their salesperson thay this 4xe is an exception.

“Things took a turn for the worse now that the weather is colder, said 4XE owner and Redditor AnotherDriver.

“I first noticed that the car would start the internal combustion engine when it was below 0 C (32 F).  I can understand the need for additional power to run climate and the drivetrain in cold weather.“

“However, this did not last long, as the Jeep soon entered the Fuel and Oil Refresh Mode (FORM). Once in this mode, the 4xe would no longer allow any electric usage. The only way to leave FORM requires driving with the oil temperature above 80 C (176 F) for a long time (almost two hours of highway driving in my experience) or resetting the oil life.“

It was much the same, arguably even worse, for Alberta, Canada resident and 4XE forum member “Mike the MillWright” and his 4xe starting in December 2021. No matter how long or hard he drove his 4xe in Winter, he could not get FORM to stop coming up.

“Drove the Trans Canada highway 1 hr at our speed limit of 110 km/hr,” Mike the Millwright commented.

“Got back to town, pulled over, shut down and restart. Went right back into fuel oil regen mode. “

FORM issues on his 4xe got so bad, he eventually traded his Wrangler 4xe for a Gladiator.

“You will find a lot of do it yourself fixes on here, I was so disappointed with Jeep I traded it in for a gladiator 41 days after purchase,” Mike commented.

“The biggest issue is the spending of gas trying to heat up your oil to get rid of the residual fuel , when for me the point of the purchase was to not use gas, you know, save the planet kind of thing, lol. Unfortunately there is at present no fix and Jeep will tell you it is doing it’s job by putting you into FORM.“

Mike the Millwright documented his struggles with FORM and, if you’re suffering from cold weather disabling EV mode in your 4xe, his posts are worth a read.

If you live in a place that gets close to freezing temps and are considering a Jeep Wrangler 4xe, it would behoove you to ask fellow 4xe owners nearby what their experience has been and if they’re forced to use FORM too often.

Otherwise, you might end up in, as those suffering from FORM issues call it, a summer-only hybrid.