Can somebody with a 760 V6 B280F tell me the value of the input resistance looking into the control unit of the temperature sensor pins (looking from the front of the car the temperature sensor is on the left of the thermostat.)
The procedure is as follow:
1) It does not matter whether the car is warmed up or not. 1) Disconnect the sensor from the control unit by undoing the plug. 2) Measure the resisances from each of the two female pins on the plug to ground with the ignition switched on (car not started.)On my car I got the values of ~2500 Ohms and ~750 Ohms. With the sensor connected and the car warmed up the voltage at these pins are ~.8V and ~2V. The resistance of the sensor itself for both pins are ~750 Ohms (there are two separate temperature sensing units inside the single sensor.) This seems to indicate that the two thermistors inside the sensor are similar but driven differently. The 2500 ohms is probably for the temperature gauge. While I think the sensor is OK I'm not sure if the 750 Ohms input impedance of the control unit is reasonable.
The reason for this test is to make sure that the control unit does know that the engine is hot from the 2V it gets back from the sensor. The .8V does cause the temperature gauge to stay exactly in the middle. At the moment no matter how much I adjust the AMM I could not see any change in the oxygen sensor test point, indicating that the car is not yet in closed-loop mode.