Is a resistance test of wheel speed sensors valid?

Not open for further replies.
Apr 27, 2010
Suburban Washington DC
I'm getting a code for implausible signal, right front sensor which is setting the ABS and ESP lights in my '13 Fiat. Checked the resistance of the sensor and it shows 410K ohms. About the same as what a spare Dodge sensor I have shows. Is resistance an accurate test for condition? I also checked for ac voltage from the sensor while spinning the wheel and got nothing. Bad sensor?
Reluctance type sensors generally have a resistance on the order of hundreds of ohms, not hundreds of k ohms. If you don't have the spec, compare it to one of the other Fiat sensors on another wheel.

The signal will be disrupted by accumulation of iron particles on the sensor or the tone ring.
Resistance test can only determine one of the less common faults from the magnetic coil itself, or the wiring/connector to it depending on where you measure. That coil doesn't tend to fail without some external stress on it like the housing breaking.

More often the end of the sensor has goop on it, likely the bearing wear putting metal particles in the grease in an internal sensor, or corrosion on the sensor ring on an external, or even a frayed wire or a fouled connector contact.

So, if you can clean the sensor without damaging it, try that, but it could be that you need to clean the sensor ring or a whole new hub if internal, and to check the wiring past the point where you did the resistance measurement.
Last edited:
I wouldn't think so. Aren't most of these sensors active with IC's in them?

How many wires, 2 or 3?

Did you do a DC check to see if it was biased at 5V or similar?
If it's cheap, then do that. Sometimes swapping parts when they are cheap is the fastest/easiest way to fix something, I call it shotgunning a repair. Sometimes it's not worth overthinking.

I've never tried a resistance check on the sensors I've seen but I'm guessing they'd read very high resistance.
Could also be a broken wire from the sensor connector to the " module " .

I was getting an ABS fault on the 2008 Silverado company truck I was driving . O'Reilley scanned it and told me it was the LF sensor . Pulled the sensor and the resistance reading was bad , compared to the new one I installed . Problem solved .

Tried the resistance test , at the sensor connectors , on a cousin's 2005 Buick Lacrosse . They all showed very close . Figured it was a bad wire . He said forget about it . He was in bad health and did not feel like pursuing it .
You can observe the sensor while spinning the target on a low voltage scale with an analog volt meter or an o-scope, if you know what you are looking at you can also use a DVM. I've come across iron cored sensors that have become magnetized over time and it causes issues. You can swap polarity of a two wired sensor if it becomes magnetized and squeeze some more life out of it.
Last edited:
Got a new sensor and resistance about the same as the old one but works fine now. So I would say resistance isn't a positive test unless you see something obvious like zero or infinite resistance.
Not open for further replies.