I have a 2005 Grand Caravan. The outside/ambient temperature reading in the overhead console (next to the compass reading) is stuck at -40 degrees. I replaced the sensor, checked the cabling (looks fine), disconnected the negative lead on the battery in an attempt to clear the computer, and even tried another overhead console unit all to no avail. I've seen this problem mentioned in this forum and other sites like fixya, but none of them have a solution posted. Is this really an obscure problem? Is there nothing to reset the onboard computer to reread the outside temp?

This is frustrating to say the least. Thanks in advance for your help.

 

Welcome to DF
I can't tell you what is wrong, but I can give you some information to do a self test.
OVERHEAD CONSOLE
Any diagnosis of the overhead console should begin with the use of the DRB III® diagnostic tool. For information on the use of the DRB III®, refer to the appropriate Diagnostic Procedures information.

If the problem with the overhead console is an inaccurate or dashed (- -) display, refer to SELF-DIAGNOSTIC TEST. If the problem with the overhead console is incorrect Vacuum Fluorescent Display (VFD) dimming levels, use a DRB III® scan tool and the proper diagnostic procedures information to test for the correct dimming message inputs being received from the Body Control Module (BCM) or Front Control Module (FCM) over the Programmable Communications Interface (PCI) data bus circuit. If the problem is a no-display condition, use the following procedures.

Inspect the related wiring harness connectors for broken, bent, pushed out, or corroded terminals. Refer to the appropriate wiring information.

Check the fused B(+) fuse in the integrated power module. If OK, go to Step 2. If not OK, repair the shorted circuit or component as required and replace the faulty fuse.
Check for battery voltage at the fused B(+) fuse in the integrated power module. If OK, go to Step 3. If not OK, repair the open fused B(+) circuit to the fused B(+) fuse in the integrated power module as required.
Check the fused ignition switch output (run/start) fuse in the integrated power module. If OK, go to Step 4. If not OK, repair the shorted circuit or component as required and replace the faulty fuse.
Turn the ignition switch to the On position. Check for battery voltage at the fused ignition switch output (run/start) fuse in the integrated power module. If OK, go to Step 5. If not OK, repair the open fused ignition switch output (run/start) circuit to the ignition switch as required.
Turn the ignition switch to the Off position. Disconnect and isolate the battery negative cable. Remove the overhead console. Check for continuity between the ground circuit cavity of the roof wire harness connector for the electronics module and a good ground. There should be continuity. If OK, go to Step 6. If not OK, repair the open ground circuit as required.
Connect the battery negative cable. Check for battery voltage at the fused B(+) circuit cavity of the roof wire harness connector for the electronics module. If OK, go to Step 7. If not OK, repair the open fused B(+) circuit to the fused B(+) fuse in the integrated power module as required.
Turn the ignition switch to the On position. Check for battery voltage at the fused ignition switch output (run/start) circuit cavity of the roof wire harness connector for the electronics module. If OK, refer to SELF-DIAGNOSTIC TEST. If not OK, repair the open fused ignition switch output (run/start) circuit to the fuse in the integrated power module as required.
SELF-DIAGNOSTIC TEST
A self-diagnostic test is used to determine that the electronics module is operating properly, and that all the PCI data bus messages are being received for initial operation. Initiate the self-diagnostic test as follows:

With the ignition switch in the Off position, on Electronic Vehicle Information Center (EVIC) and Compass Mini-Trip Computer (CMTC) equipped vehicles simultaneously depress and hold the STEP and the RESET buttons. On Compass Temperature Module (CT) equipped vehicles depress the C/T and the US/M push buttons.
Turn the ignition switch to the On position.
Following completion of these tests, the electronics module will display one of the following messages:
Pass Self Test (EVIC only), PASS (CT, CMTC) - The electronics module is working properly.
Failed Self Test (EVIC only), FAIL (CT, CMTC) - The electronics module has an internal failure. The electronics module is faulty and must be replaced.
NOTE: If the compass functions, but accuracy is suspect, it may be necessary to perform a variation adjustment. This procedure allows the compass unit to accommodate variations in the earth's magnetic field strength, based on geographic location. NOTE: If the compass reading display is blank and only “CAL” appears in the display, demagnetizing may be necessary to remove excessive residual magnetic fields from the vehicle.

 

Usually a broken (corroded) wire pretty close to the connector. You should be able to short the connector and the overhead should read SC.

 

Are you referring to the connector at the overhead console, the sensor or in the passenger-side door column? I checked all three and didn't see any splayed, crimped, corroded or otherwise damaged wires or connections. I tried shorting the connector going to the sensor with no change in the reading. The temp still displays as -40°F with the connector unplugged from the sensor. Is there a fuse for the overhead console?

The self-test passed.

Seems like there is a problem between the sensor and the overhead console. I'm not familiar enough with the engine compartment to know where to look or what to look for. Is there a master reset for the BCM? Could the BCM be malfunctioning?

 

Was the sensor still connected to the mounting? Usually the harness gets pricked under the lower radiator cross member and corrodes. The high resistance won't give the open circuit signal in the display. If you unplug the sensor, the display should read OC and if you short it, it should read SC. If it doesn't, it's because the wire is very corroded giving the high resistance in the circuit.

 

1999 Grand Caravan, 3.3L engine.
I have the same problem as described by others on this forum. The Outside Air Temperature (OAT) on the overhead console started by being very eratic showing temperatures all over the clock. It is now stuck at O deg C. (in Canada). From earlier posts on this forum I found the location of the sensor on the front bumper and the bracket is broken with the sensor hanging by the wires. Is there a chance that my problem will be eliminated when I replace this sensor and are there any special checks I should do when I have the bumper parts removed to provide easier access to the sensor?

 

Welcome to DF
Try replacing the sensor and fix the sensor to a bracket. Or make one. You just don't want the sensor hanging by a wire.

 

Sensor has been replaced all wires checked and they show no signs of wear or corrosion. Indicator still frozen at OC . does this mean an "open circuit".
I can do without an outside air reading but hope that this does not affect the engine start in cold weather.

 

Yes, that does mean open circuit. The wires usually break right by the sensor when it gets drilled by the rock or whatever breaks the bracket. You should be able to give them a little tug and break the wire if it is. a connector kit is available from your local dealer, part number 05013948AA and goes for around $25.00

 

Thanks to Mastertech and Tizzy1. I replaced the sensor and the wiring cable and all is now working. I have become quite adept at removing and reinstalling the front bumper cover to get at the ambient air temp sensor. Had to purchase the connecting plug and cable from a Dodge dealer for a cost of $51 Cdn, I am glad I was able to do this repair and not pay a labour fee of $80 or so per hour. Glad I was able to get help from this forum