Please do me a favour - 760 V6 B280F

[Duong Nguyen]

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.

 

[Duong Nguyen]

2) Measure the resisances from each of the two female pins on the plug
to ground with the ignition switched on (car not started.)

This is meant to be:

2) Measure the resisances from each of the two female pins on the plug
to ground with the ignition NOT switched on (car not started.)

 

[radietz]

This is meant to be:

2) Measure the resisances from each of the two female pins on the plug
to ground with the ignition NOT switched on (car not started.)

I have no idea what the number should be, but the voltage on the other
end of the wire, backprobed at the fuel injection computer (ECU) plug
(terminal 2) should rise with the temperature of the motor. AFAIK all
coolant temp sensors are NTC (negative temperature coefficient) so as
the temp rises the resistance decreases. The other gray wire goes to pin
2 on the ignition control unit (ICU). The fuel control wire passes to
the main harness via Plug D (2X4) pin 4 near the coolant
overflow/reservoir. The ignition wire passes to the main harness through
plug F (2X4) pin 2 below the left side upper strut gusset.

There have been many problems with these plug connectors. Mostly in that
the male pins pushed out of the plug housing during assembly.

The resistance values between ground and pin 2 at the ECU should be:
-10C (14F) 8260-10560 ohms
+20C (68F) 2280-2720 ohms
+80C (176F) 290-364 ohms

If the throttle switch is open resistance between pin3 and ground at ECU
is >0 ohms the MAF sensor will not adjust, nor will you see any feedback
at the test point. If the TPS does not make an audible click when the
throttle is cracked odds are it's out of adjustment, the throttle
housing is full of goop, or it's defective.

To check the mass meter: Ground terminal 21 at the ECU, (switches ECU
relay on). Measure voltage between MAF terminals 1 (ground) and 5. You
should see B+. Disconnect the ground jumper on ECU 21. Measure the
resistance between MAF terminals 6 and 7: should be ~3-4 Ohms.
Resistance between 6 and 14 should be 0-10,000 Ohms depending on the
position of the CO adjustment screw.

To check the O2 sensor preheater: Resistance should be between 3 Ohms
(20C~68F) and 13 ohms (350C~662F).

HTH

Bob