I just picked up a Digital Multimeter today and thought I could use it to check on some things in the car. Only problem is I havent used one of these guys for years I want to start off by checking a few basic circuits on the car but aren't too sure how to start off doing it. How do I go about checking things such as the MAF, MAP, TPS, 02's, etc? Most of the sensors are resitance based right? (Ohms?)

What I want to know is:
Where can I find a table/chart listing normal readings for sensors?
What sensors are good starter sensors to test for me ?
Any tips for doing this?

I've got a 95 Z28. Thnx for any advice =]

 

If you pick up a Haynes manual it tells you what most of the sensors should be reading.

 

Thanks, Found the section and found it very straight forward =]

 

Some thoughts on the sensors:

MAF - You need a frequency meter to check the output. You can check for +12V power supply at the meter

MAP - resistance, with +5V bias voltage from PCM
IAT - thermistor (resistance)
Coolant Temp - thermistor (resistance)
TPS - Resist, with +5V bias from PCM

KS - variable frequency riding on a reference voltage. +5V bias from PCM, pulled down to 2.5V by sensor. In essence, it is a "microphone".

O2 - millivolts, but be careful. You can destroy the sensors if your meter puts too much current through them. Most modern digital meters are OK because they are very high impedance. And, the readings you get with a volt meter can be off as much as 0.3V from what the PCM sees. PCM supplies 450mV signal, and the O2 sensor element adds or subtracts from it.

IAC - not a sensor, but an actuator. Responds to position instructions from PCM.

You also might want to reads my "scanner" writeup.. include things like resistance values for various temps on thermistors, and for kPa/"Hg on MAP sensor.

SCANNER WRITEUP

 

Great info Injuneer.... This stuffs tonnes of fun I'm going to throw that document onto my palm for some fun reading later. I guess my next step is to get the connector for my OBD I system and laptop/palm software to mash around with the data.