2nd Gen Non-Engine/Transmission -40 Degrees????

[Curious Dave]

Ok... Here we go. I can not find anything listed in the old postings... I am probably looking in the wrong area.



Problem - The overhead temp gauge / computer has read strange temps for a few years now. It usually corrects itself once I get out of the sun or drive around for a bit. But today it said -40 degrees. If I was in northern Canada I could maybe agree... . But I am in the plains of northern Oklahoma.



What is going on with this thing and how do I fix it?

 

[jelag]

The fuel system needs correct ambient air temperature and pressure to meter fuel correctly so the ECM is connected to sensors that give it that information.....

As an accessory the ECM supplies a display the ambient air temperature for your use... . you either have a sensor sending the incorrect information to the ECM, or the ECM is sending the wrong data to the display in the overhead... . in either case I'd have them check it with a scan tool... .

With the scan tool they can tell if the sensor is right or the ECM is sending the wrong data to the overhead display. .

Incorrect information can cause excessive use of engine preheat features to say the least as well as incorrect fuel delivery... .

 

[Bob Cochran]

There are a lot of trucks that do not have the overhead temperature so it makes me wonder if this is the same sensor the ECM uses. I always thought it was getting the engine water temperature and IAT or is that AIT to perform this function?

Anyways on mine that temperature sensor is located behind the hood grill guard toward the top. You will see the wire running to it as it is the only electrical item on the hood except the engine convenience light.

 

[JoeBioDiesel]

I repectfully disagree with Jim.



The 2001 Dodge uses an ambient temperature sensor that is plugged directly into the overhead console. It is located out in front of the radiator. It has 2 wires to it. When it reads -40F, it means that the signal wire(purple with a green stripe) has 5 volts on it. The sensor pulls that wire to a lower voltage as the temperature rises. It should be way less than 5V. Grab your multimeter and test it.



Although I haven't researched it, I don't believe that this sensor is used for fuel control. I'm pretty sure the Intake Air Temp Sensor is used instead.



Joe

 

[JDiepstra]

I repectfully disagree with Jim.



The 2001 Dodge uses an ambient temperature sensor that is plugged directly into the overhead console. It is located out in front of the radiator. It has 2 wires to it. When it reads -40F, it means that the signal wire(purple with a green stripe) has 5 volts on it. The sensor pulls that wire to a lower voltage as the temperature rises. It should be way less than 5V. Grab your multimeter and test it.



Although I haven't researched it, I don't believe that this sensor is used for fuel control. I'm pretty sure the Intake Air Temp Sensor is used instead.



Joe

I would go with this. I had a problem with mine reading wrong and come to find off the sensor was broken clean off!

 

[KLockliear]

I repectfully disagree with Jim.



The 2001 Dodge uses an ambient temperature sensor that is plugged directly into the overhead console. It is located out in front of the radiator. It has 2 wires to it. When it reads -40F, it means that the signal wire(purple with a green stripe) has 5 volts on it. The sensor pulls that wire to a lower voltage as the temperature rises. It should be way less than 5V. Grab your multimeter and test it.



Although I haven't researched it, I don't believe that this sensor is used for fuel control. I'm pretty sure the Intake Air Temp Sensor is used instead.



Joe

EXACTLY - that sensor is ONLY used for the overhead display. Check for a wiring issue or replace the sensor.

 

[SSolderitch]

At a truck show. . I saw the sensor mounted inside the grill and was wired into the hood light harness. I had to think what it was, because I don't have one, then I remembered - outside temp sensor. He also had leather seats... part of a good old mopar convience or leather package. Every chrysler lhs, concord, etc will have the same sensor, junkyard=cheap.

 

[AllianceDiesel]

ambient temp sensor has nothing to do with fuel/ecm, its only have to do with the overhead control module, the intake air temp sensor is what is used by the ecm



as far as your condition, either you have a open, which should read OC on the overhead or you got a short to power, it does take some time to update the temp because there is stagnent heat sitting around the sensor when the vehicle is sitting, once you go a certain distance at a certain mph then it starts to read the sensor.

 

[icman95]

As SSolderitch said, this computer was part of the leather package. I wanted the leather for dog hair purposes, but tried to opt out of the overhead display for exactly this reason. Just one more thing to break/go wrong. I never had much faith in the fuel mileage readings it gave, although they were better than I thought they'd be. Of course, Mother Mopar wouldn't let me opt out of it if I wanted leather, so I got it. I guess the temp reads close to being right, but at least now I've learned from this thread what to do if or when it starts to act up on me.



Good luck.

 

[Road Dog]

I like the overhead console for the temperature and compass. I like to know when the roads are icing up and the compass is handy on forest service roads.

 

[AllianceDiesel]

My fuel mileage is spot on and so is my dads on his 06, my jeep grand cherokee is only off by a tenth.

 

[Curious Dave]

Thanx guys... I will snoop around and see what I can find.

 

[icman95]

Before I did my mods, the fuel reading was usually off by at least 1/2 mpg. Sometimes I had it off by 1. 0mpg, though not too often. A tenth or two is no problem. More than that, not so good. Of course the mods killed the computer's ability to accurately measure mileage, and I don't blame it for that. Now it reads average mpg of 26 when reality is 10 lower than that. Again, in this case, can't blame the computer.