View Full Version : Ambient air temp issue

02-08-2013, 03:24 PM
I have been working on this problem for a couple months now my temp gauge on the dash bounces around like crazy reads from -40 up to actual temp and is constantly changing sometimes it has no reading at all just two blank lines. so far i have changed the sensor behind the plate twice and the gauge cluster once, i have completely stript everything around the harness to look for damage both under the hood and under the dash. i have noticed that while working under the dash that the temp changes more quickly but i cant watch it while under the hood so im not sure if im onto sumthing there. because this puts my van into limp mode when it reads around -30 to -40 it is a problem i cant live with. hoping someone else has had this problem

02-08-2013, 05:03 PM
It's likely there's an intermittent open between the sensor and the dash. I would use an ohm meter to track it down. Follow the schematic diagram.


Aqua Puttana
02-09-2013, 03:35 PM
It's likely there's an intermittent open between the sensor and the dash. I would use an ohm meter to track it down. Follow the schematic diagram.

Seems likely.

I would first disconnect the battery negatvie, remove the Instrument Cluster IC, access the C1 connector, remove the connector, visually inspect the pins, etc. and re-install. Even if no problem is found the action of C1 connector R&R may help to restore good connection.

The symptom description sounds intermittent. If the R&R of connector C1 doesn't improve things I would consider running a separate 2 conductor cable from the IC to the sensor to completely eliminate the possiblity of a harness problem. If the replacement cable corrects the problem I'd likely go no further.

Connector C1.

Wire Colors

BL/DG = Ambient Sensor Signal (+)
BR/DG = Ambient Sensor Signal Return

Pin #11 and Pin #2 on instrument cluster

Wiring Diagram 8W-40-4, 8W-40-8



Maybe inspect the harness for damage where some harnesses were pulled through with a metal hook during re-assembly in North America?

Some suggestions. Not a diagnosis. vic

02-12-2013, 02:39 AM
great i will try that Thanx

02-12-2013, 02:50 AM
Don't forget that the sensor is mounted (effectively) behind the front license plate... i'd look at that connector (and nearby wire) first.

a "-40" reading indicates infinite resistance (i.e. an open wire or connection).
A short-circuit (across the sensor) would read +255
(i don't know what shorting either of the wires to chassis metalwork would produce as a reading)


03-07-2013, 02:08 PM
I am finally going to attempt to find this problem today i eventually had to remove the sensor to keep the van out of limp mode, the problem now is the gauge was reading high also, it will jump from minus 40 to plus 55

03-07-2013, 03:37 PM
As you can see in the above schematic, the temperature sensor is a variable resistor. You can rule out a defective sensor by unplugging sensor and sticking a resistor into the connector. I don't recall the sensor's resistance range, but I guess somewhere around 4.7 k ohm should work. Any size wattage is OK. If the temperature display still bounces around then the sensor is OK.


03-07-2013, 06:31 PM
So i ran two new wires from the sensor to the insterment cluster and problem solved! thanx for your help

11-02-2013, 10:14 PM
I have a question (2005 2.7L Sprinter) re: ambient air temp sensor and CHECK ENGINE light.
I have 102k miles and the dash instrument no longer displays the outside air temp. Simultaneously the CHECK ENGINE light came on. There are no driveability issues, and after the dealer scanned and did diagnostic, determined that the two are related.
I would just like a 2nd opinion, as there are no driveability issues, and tech said ok to drive (I was on a cross country trip when it happened).
They quoted about $32 for the part (it's in the front bumper I understand thanks to other posts here). But $140 for labor to replace seems far fetched for what sounds like a 10 minute job if I read other posts correctly.
To summarize: are the 2 items related, and is it a simple fix (and makes the CHECK ENGINE light go out)?


11-03-2013, 01:47 AM
To summarize: are the 2 items related, and is it a simple fix (and makes the CHECK ENGINE light go out)?

Yes, they're related (a bit)... the ECM has an error code for when the ambient air temp and the Intake Air Temp disagree (an error would be the Ambient being hotter than the Intake)

Simple fix? Very: crawl under, unplug old sensor, squeeze to remove from its hole, plug in new one, push it into its hole.

Here's the service manual's take on it (service manual available at http://aie-services-2.net/Sprinter/ )


Will it make the CEL go out? Who knows?


11-05-2013, 11:01 PM
Lo and behold, problem solved after pulling the license plate holder and merely reconnecting the plug to the sensor (it had come apart enough to disconnect - why the original dealer diagnostic didn't find this is beyond me...).

CHECK ENGINE light stayed on till ignition key was cycled 4 or 5 times. It's off now and all is well again with the MB Cruiser.

Thanks to all on this forum.....I appreciate happy (i.e. $0 cost fixes) endings.:thumbup:

12-15-2013, 03:46 PM
This is mildly related, but doesn't seem significant enough to warrant a new thread so thought I'd ask. Do other people notice that their ambient temperature reading increases when they are idling or even stopped at a light for an extended period? It has been between 0-20F almost non-stop recently, but when I start the engine in the first 5 minutes the reading will go from the actual outside temperature, to between 5-15F higher. As well, once the engine is warm, if I stop at a light the temperature will begin to climb.

I'm trying to figure out why my gas mileage has decreased by 6-8mpg over the last couple months. I can't find any turbo leaks (other than some residue next to the intake temp sensor on the intercooler to egr hose but from other posts this seems normal). I'm wondering if there is a leak I can't find maybe releasing hot air. I've recently changed my oil, checked for black death, cleaned my egr, maf sensor and started using winter additive in my fuel. But as well went to 16 inch rims and bigger tires. That said, my mpg has gone from 28-30 in the summer to 20-21 now. Maybe it is time for a new egr but I'm trying to troubleshoot other options first. Thank you!

12-15-2013, 03:58 PM
The mileage drop is unusual. I assume you made the odometer correction for the larger tires? And if so, maybe a new temp sensor would be in order. Just some thoughts on the matter.


12-15-2013, 04:21 PM
From milepost markers I think I am underestimating mileage on my odometer by about 7% (went with 225/75 R16 A/T tread). So at the pump if I calculate 20mpg, I know it is actually 21.4mpg. I do drive 60mph on the highways as suggested on a thread here, so 20mpg for my short, middle length van seems low. I could see the more aggressive tread and bigger tires decreasing efficiency a bit, but not 6-7mpg. My last tank was the worst, as for the first time ever I was under 20mpg (19.96mpg, damn, just barely!). This ambient temperature phenomenon seems to be more pronounced in the last several weeks, but the winter temperatures only arrived recently so perhaps the gradient from engine temperature to ambient temperature has increased to the point where I am noticing it more, or it has become worse. Either way, I'm not getting any CEL or MIL showing, but I don't have a DAD or fancy computer. But my mpg seems to be decreasing a bit every tank, but the engine seems to have full power and be running well.