Hi,

Just curious if anyone else has gotten this code before? I just recently started getting it after I replaced my old ECT sensor (new sensor is only about 1 week old).

My car threw a belt just before this code came up -- heated to 245 and coolant overflowed. I replaced the belt tonight and refilled the coolant. When I started the car the sensor read "LOW", then went to "xxx" (which shows up when it can't read the signal from the sensor), then it went to 88* F, then it threw the high voltage code. Shut her down, checked the sensor (looks alright to me), and turned her back on... same thing... started reading the temp appropriately for a little while, then went to "xxx" and threw a high voltage code.

Where should I start looking? Could it just be a bad sensor? What should the input voltage be on the sensor? How "smart" is the ECT sensor? If for some reason the input voltage was high, would the ECT also output a high voltage signal?

Help!

 

 

Haven't heard of this one. Here is what I have:
CIRCUIT DESCRIPTION
The Engine Coolant Temperature (ECT) sensor contains a semiconductor device which changes the resistance based on the temperature (a thermistor). The ECT sensor is mounted in the left bank cylinder head near the front of the engine. The ECT sensor has a signal circuit and a ground circuit. The PCM applies a voltage (about 5.0 volts ) on the signal circuit to the sensor. The PCM monitors the changes in this voltage caused by changes in the resistance of the sensor in order to determine the coolant temperature.

When the coolant is cold, the sensor (thermistor) resistance is high. The PCM's signal voltage is only pulled down a small amount through the sensor to a ground. Therefore, the PCM senses a high signal voltage, or a low temperature. When the coolant is warm, the sensor resistance is low. The signal voltage is pulled down a greater amount. Therefore, the PCM senses a low signal voltage, or a high temperature. At normal operating temperature, the scan tool should display an ECT value of 1.5-2.0 volts .

When the PCM senses a signal voltage higher than the normal operating range of the sensor, this DTC will set.

CONDITIONS FOR RUNNING THE DTC
The engine run time is greater than 60 seconds .
OR
The engine run time is less than 60 seconds when the IAT is greater than 0°C (32°F) .

CONDITIONS FOR SETTING THE DTC


The ECT is less than -39°C (-38°F) .
Conditions met for 20 second .
ACTION TAKEN WHEN THE DTC SETS


The PCM illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records.
CONDITIONS FOR CLEARING THE MIL/DTC


The PCM turns the malfunction indicator lamp (MIL) OFF after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A last test failed (current DTC) clears when the diagnostic runs and does not fail.
A History DTC clears after 40 consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures.
Use a scan tool in order to clear the MIL/DTC.
DIAGNOSTIC AIDS

IMPORTANT:


Remove any debris from the PCM/TAC module connector surfaces before servicing the PCM/TAC module. Inspect the PCM/TAC module connector gaskets when diagnosing/replacing the modules. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM/TAC modules.
For any test that requires probing the PCM or a component harness connector, use the Connector Test Adapter Kit J 35616-A. Using this kit prevents damage to the hamess/component terminals. Refer to Using Connector Test Adapters in Diagrams.
If the engine has sat overnight, the engine coolant temperature and intake air temperature values should display within a few degrees of each other. If the temperatures are not within 3°C (5°F) , refer to Temperature vs Resistance. See: Specifications\Pressure, Vacuum and Temperature
If you determine that the DTC occurs intermittently, performing the P1115 diagnostic table may isolate the cause of the fault.
For an intermittent, refer to Symptoms. See: Diagnostic Information and Procedures\Symptoms
TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.


This step determines if the malfunction is present.
If both DTCs P1635 and P1639 are set at the same time, this indicates the IAT signal circuit is shorted to a voltage.
Using the Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature, etc.) that you observed. This will Isolate when the DTC failed.
An engine coolant temperature above 139°C (282°F) indicates the PCM and ECT sensor wiring is OK.
An engine coolant temperature above 139°C (282°F ) indicates the PCM and ECT sensor signal circuit is OK.
Disconnecting the PCM allows using the DMM in order to test continuity of the circuits. This aids in locating an open or a shorted circuit.
Disconnecting the PCM allows using the DMM in order to test for a short to voltage.
This step is testing for another circuit shorted to the ECT signal circuit.
Inspect for proper terminal tension/connections at the PCM harness before replacing the PCM

 

The sensor is cheap and easy to change, I'd say get another one and see if that fixes it. From the sound of it I'd say the sensor is semi shorted internally and as it heats up with the engine the internal resistance weakens and it goes direct short.