Chrysler Repair: error code P0073, radiator grille, violet light

Question
I have a 2005 caravan.  It shows an error code of P0073.  What is that

Answer
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Hi Scott,
The ambient temp sensor signal is off-value so much as to not make sense to the  integrated power module. That sensor is located on the front of the panel upon which the radiator sits that runs laterally across the van (or possibly to the right side of the headlamp mounting module grille opening, behind the radiator grille but in front of the engine compartment. It has two wires that go to the front control module of the intergrated power module on the left inner fender of the engine compartment. It has two wires, violet/light greem and violet/brown that go to pin 9 and 18 of the light green/red plug at the power module. You would begin by checking the resistance across the pins of the sensor, after removing its plug. The only two reference temperature points I can give you are -40F (336 kilo-ohms) and +140F (2.49 kilo-ohms), you could interpolate between those two values for other temperatures (9-11 kilo-ohms at 68F). If the resistance seems reasonable, then I would suggest checking the continuity of the wires from the plug socket to the intergrated power module plug's pins and also check that neither is shorted to ground. I believe that the violet/brown wire should show 5V to be present when the ignition switch is in the run position. The code says the signal from the sensor is at too high a volage which suggests that either the resistance is much lower than say about 9-11 kilo-ohms at 68F or that the two wires are shorted together so that the violet/light green wire is also showing 5V.
The signal is what causes the local temperature to be displayed on a readout in the cabin. My information is from the '02 manual which should apply to your '05 but I can't guarantee it.
Roland