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I have a 2008 Jeep Wrangler JKU:
6-speed manual; Dana-60 axles (5.38 ratio); 4-inch lift kit; 38-12.5r17 tires; Pypes Cat-back off-road exhaust; and OEM air intake (running K&N reusable air filter) – 125K miles on vehicle and stock motor. 12K winch is buried in SRC Pre-runner bumper – so no airflow restrictions.

Operating temps have never, ever been an issue – until I recently towed a trailer in highway summer conditions (100 degree ambient air) on Baker, CA grade (east and west bound), as well as, eastbound up to St George and beyond on I-15. Trailer is 2-axle , 14-foot enclosed - with 1000 lbs Harley as load (approx. 4500 lbs gross weight). Also, in idling/crawling in SW desert conditions – where fan stays on for extended periods of time in Lo-4.

In an attempt to improve the cooling system – using OEM only parts they offer in Middle Eastern countries for JKs, I have added the mechanical fan shroud, thermostatic fan clutch, and fan blade – which are installed over a stock electrical fan and slightly modified electric fan shroud (trimmed to fit inside new mechanical shroud and mount to same mounting points) as additional capacity during projected high heat events.

In the four days since I’ve had this new setup installed (Jun 24th), I have tripped P0128 and P2181 codes three times.

I replaced original coolant, hoses and thermostat (195 degree) with OEM parts one month (May 20th) before I pulled the trailer in summer conditions (2017 Memorial Day weekend – Baker, CA registered 103 degrees at 1pm when I past westbound on I-15). Have had absolutely no faults in the life of this vehicle (guess they don’t make them like this anymore, eh?)

I am not having an overheat issue, rather, it runs 30+ degrees cooler without any trailer loads – approx. 160 degrees on OBD scanner. If I let the jeep idle for over an hour, it will finally reach OEM operating temp (190+), and then cools right back down to approx. 160-170 when rolling 25+mph . I don’t get a code trip when I do that. It’s during cold starts in morning on commute to work, or, short trips to market when vehicle is not allowed to warm-up that the codes trip.

Can the ECM be sufficiently remapped to eliminate these code-tripping conditions?

Can I get a different Coolant Temp Sensor that tricks the ECM? Can I drill a bleed hole that directly hits the sensor tip?

Can I get a different thermostat that keeps the Coolant Temp Sensor reading the actual hot engine temps? (bleed-hole type, or, larger bleed-hole)

Does the electric fan switch also provide input to the ECM that would require relocation of the sensor to a location other than on the mechanical fan shroud (the electric fan shroud had the sensor less than 1-inch from radiator fins – new mechanical shroud has it almost 3-inches away from the radiator fins)? The mechanical fan interfered with leaving the sensor in the original location on the electrical fan…

This setup is absolutely awesome, and, FCA (then Mercedes) should have told the US EPA to go pound sand when they were forced to remove the dual mechanical/electrical fan setup for US consumer usage, but they didn’t.

What mods do I need to do to make this vehicle stop reporting such ‘false failure’ conditions?
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