QuestionI have a 2006 Jeep Grand Cherokee and the ambient temperature reading is constantly inaccurate. On a 79 degree day it indicated 60. The dealer changed the sensor with no change. They then indicated that Daimler Chrysler told them that the vehicle must be driven at a speed of 35 - 40 mph for 2 - 3 miles without touching the brakes before the reading will be accurate. As a side note, some days the reading changes within 1/10 of a mile and some days it don't change at all until I drive on the interstate for several miles. Any advise? Is this normal or not? I did test drive a 2007 JGC and the Temperature changed within the first 1/10 - 3/10 of a mile. Anything you can tell me will help on where to go from here.
AnswerBob,
This has been an issue for years on a *lot* of vehicles, and accuracy and refresh rate is always sporadic. That said, some seem more accurate than others. I feel your pain, though, since more than a few service departments feel they have bigger fish to fry than ambient temp accuracy. Other times, technicians sometimes fall prey to 'parts-changing', primarily because the factory pays them slave wages for something like this. They'd rather slam a part in, and get to the next vehicle, since they'll be paid for approximately 20 minutes time. Sometimes, that's just enough to get the car, stand in line for the part, replace it, and park the car. I feel for these guys, but that shouldn't belittle your issue. Sorry for the mini-rant; the actual principal of accurate problem diagnosis gets obfuscated by trivial stuff, and the customer sometimes suffers.
Back to the problem... if your vehicle was built "prior to January 1, 2006 (MDH 0101XX) and vehicles equipped with a 5.7L engine (sales code EZB) WITHOUT Trailer Tow Group (sales code AHT) built prior to March 1, 2006 (MDH 0301XX)", then it may be subject to Technical Service Bulletin (TSB) # 08-005-06 rev B. The title is "Outside Ambient Temperature Reading Inaccurate As Displayed By Instrument Cluster". The repair involves reprogramming the Front Control Module (FCM) with new software.
Ok, I'll go out on a limb and say the dealer has either already done this, or your vehicle falls outside the parameters of the bulletin. If it were *my* shop, that's the second step to any diagnosis -- check for TSB's. However, sometimes this gets overlooked, at the expense (time, etc) of the customer. Also, even though your vehicle *may* fall outside the TSB range, that doesn't take away the possibility that an FCM flash wouldn't help. I've flashed many vehicles that were outside -- most were unaffected, but some issues were addressed.
Aside from that, the dealer does have higher resources they can call upon -- like STAR online. This is information that DC/Jeep field engineers accumulate, and they make it available to the service techs. Going further, they can call STAR and work with a type of factory 'help desk', to address seemingly unfixable issues. Barring that, at the local level, politely chatting with the Service Manager usually gets a better result than working through the Service Writer. Whatever the case, good luck!
