im trying to test out my sensor to see if im getting the right voltage to every sensor. so i have this instruments with Volts,Ohms, and it has 200m/ 2 / 20/ 200/750 etc..and it has a black wire and a red wire. what do u set the swtich to to test out the sensor?

 

200mV = .2V, just to let you know.

You'll want to set the 'volt' scale to whatever number is just higher than the voltage you are expecting to read. For example, if you measured the car battery, you wouldn't want to put it on the '2' scale (it should just read OL - overload, which won't damage it, so don't worry) seems as how the battery puts out up to 15V - so the '20' scale is more appropriate here.

Since just about all the sensors in our car use a 5V reference, the '20' scale is your best bet.

However, lets say you wanted to measure the O2 voltage; It only swings up to 1V max so obviously the '2' scale is going to be more appropriate (and more accurate).

The black lead is your reference which almost always goes to a ground spot. The red lead is what you use to make measurements.

There will also be times when you want to check the resistance of a sensor (or to see if the wires connecting them to the ECU are open or shorted) - examples would be the IAT and ECT (intake temp and engine coolant temp) and the O2 heater element.

What sensor in particular are you checking?

 

what about measuring resistance of injectors or the like?

 

To measure the resistance of anything, absolutely no power can be applied to the circuit - so in order to measure the impedance of injectors, simply unplug them from the main engine harness and place the red and black leads across the two terminals of the injector.

More than likely the meter has the same 'scales' for resistance as it did for voltage and since high-impedance (saturated style) are in the 12-14ohm area, the meter needs to be set to the '20' scale otherwise you get the same OL (overload) error.

Lets say you wanted to measure the resistance of the 3 sensors inside the distributor - again, unplug the dizzy from the main engine harness, locate the two wires per sensor and place the red and black leads across them. If OL comes up, keep cranking the scale up till you get a reading.

Same goes for the O2 heater element - need to unplug the O2 sensor from the main engine harness.

Same goes for IAT, ECT and TPS - need to unplug them.

You can measure the IACV impedance too - just unplug it.

For resistance and voltage specs though, you should really consult a Helms manual.

When you make resistance measurements, the actual meter sends out a small electrical current through whatever you're testing which is why you can't have any power applied to the circuit when doing this test.

 

wow. hey thanks for the writeup, i really appreciate it, imma go test out my sensors now, imma save this post so i can come back and view it