View Full Version : Not understanding instructions for testing resistance in ohms for certain components

09-09-2011, 10:47 PM
Trying to diagnose a dtc\odbII code and the instructions say the component should be in a certain ohm range at 68 degrees, am I missing something or do I need to put the component in the freezer until it reaches the correct temp., LOL. Any help would be greatly appreciated.

09-09-2011, 11:13 PM
Hi jollymonsingz,

Resistance in a component can change with temperature to some extent, depending on the component. Now, if it is a thermistor-type component, such as an Engine Coolant Temperature sensor or an Intake Air Temperaure sensor, it will CERTAINLY change with temperature, as that is what it is designed to do. The lower the temperature the higher the resistance, and vice versa. If it is a component with a static (non-changing) resistance, such as a fuel injector, then 68-degrees would generally be considered "room temperature," but wouldn't change very much if it's hotter or cooler than that.

09-10-2011, 02:15 PM
I got a "p0507" dtc, for a 2001 hyundai elantra, so I was testing the ISC and the TPS. So what you saying is the numbers in the book should be fine checking a cold engine?

09-10-2011, 04:38 PM
The ISC is reading high per the book, terminals 1 & 2 are supposed to be 10.5 - 14, I get 18.2 and terminals 2 & 3 are supposed to be 10 - 12.5, I get 16.1. I put my laser themometer on the ISC temp. matched the air temp outside which is 85 degrees.

09-12-2011, 03:47 PM
Resistance values are kind of "approximate" and can fluctuate with temperature changes, so I don't think I'd replace the part based on those readings. If it was way out of range that would be a different story (like if it was open or shorted).