HiCustomer Thank you for asking your question on JustAnswer. The other Experts and I are working on your answer. By the way, it would help us to know:-How many miles are on your Car?-WHat do you mean that the temp gauage bottoms out?-What have you already tried?
-Are there any codes in the computer?Thank you again for trusting us with your problem. Please reply as soon as possible so that we can finish answering your question.
Do you have a scanner? Can you read the data stream when this occurs?
I take it the engine still runs just fine when this happens?
TRY ONE OF THE FOLLOWING
Here is the complete wiring diagram for the UART system. Be sure that you have disconnected each module one at a time.
DESCRIPTION The Diagnostic Energy Reserve Module (DERM) performs several system functions. These functions include energy reserve, malfunction detection, malfunction recording, driver notification and frontal crash recording.
OPERATION The DERM is connected to the SIR wiring harness by a 24-way connector. This harness connector uses a shorting bar across certain terminals in the contact area. This shorting bar connects the AIR BAG warning lamp to ground when the DERM harness connector is disconnected. This will cause the AIR BAG warning lamp to come on steady whenever the ignition switch is at the Run, Bulb Test or Start positions with the DERM disconnected.
The coolant temperature gage is also operated by two coils. Battery voltage is applied to both coils. One is grounded directly and the other is grounded through the Gages Engine Coolant Temperature (ECT) sensor. This has 55 ohms resistance at 127°C (260°F) and its resistance becomes greater at low temperatures. It is approximately 1400 ohms at 38°C (1 00°F) . This causes the current through the sensor and one coil to increase at the coolant temperature increases. This moves the pointer.
DO you know were the voltage on this UART line is supposed to be generated from?
Each module has the potential to produce a 5 volt reference and pull it down to 0 volts. It is suppose to be a 0 to 5 volt square wave form.
Please do me a favor.... List every module you have disconnected on this circuit.
YES! You are correct! Make sure you have dissconnected this module!
Floorpan, Under Driver's Seat, SDM Module
WHat about the radio? Is it an after market radio? Have we tried to disconnect it and see if that helps?
WHat dark green wire are you talking about?