What are the correct ABS sensor Ohms readings for a 02 X????

[sacomstock]

Vehicle information: 2002 Explorer XLT 56K miles 4X4. Stock all around except my XM radio.


I need to see if anyone knows off the top of their head what the correct Ohms reading from all three ABS sensors for a 2002 Explorer. All I have found online are the reading for a 91-99 Explorer those are:
Front (both left and right): 0.270-0.330 k Ohms
Rear: 0.8-1.4K Ohms

After testing mine trying to narrow down why my ABS light is on I got these results:
Front Right: 0.807K Ohms
Front Left: 0.790K Ohms
Rear: 0.817K Ohms

If the ABS from a 91-99 Explorer is the same or basically the same as the 02 Explorers then I am guessing both my front sensors are bad?? Does anyone else concur? Thanks

 

[ExplorerDMB]

I do not know off the top of my head - but I wouldn't see why there would be a change in sensors (ohm wise) for the ABS module/sensors. Odd, though, to have two front ABS sensors bad. Call up Ford or a shop and see if they'll give you the information off of Alldata or their computers.

-Drew

 

[sacomstock]

From everything that I've researched, when the sensor goes bad it should give off an open reading. But I don't know not my field of expertise. Also I was just looking on www.fordpartsnetwork.com and it listed the front/rear speed sensors at $100+, from my understanding they were only suppose to be like $20 or so. I will give ford a call tomorrow and see if they will tell me and post the results back here in case anyone else needs it. But for now, I am off to work gotta love shift work in the Navy!

Thanks,
Steve

 

[gijoecam]

There is no "correct" resistance for the ABS sensors. They are a hall-effect sensor and will generate a particular voltage at a particular distance from a particular exciter ring. The ABS computer simply measures the rate of change in the voltage (which is a function of wheel speed) over a given time period and can tell if the wheels are stopping too quickly.

Indeed, they generally register as open when they fail.

-Joe

 

[sacomstock]

Okay, one last question as I try to understand how all this works. With the hall-effect sensor, if the exciter ring is not moving and the sensor is basically sitting there inside of its mout, wouldn't there be a specific resistance range when there is no voltage or magnetic flux? I'm assuming that since I am getting a mesaurement of resistence that my sensors are working correct and it is time to take it to Ford and have the ABS error code read. Just trying to understand how the whole system works. Thanks for the responses!

-Steve

 

[gijoecam]

Anti-Lock Brake Sensor

The anti-lock brake system uses three variable-reluctance sensors to determine vehicle speed. The anti-lock brake sensors operate on magnetic induction principle. As the teeth on the anti-lock brake sensor indicator rotate past the stationary sensor, a signal proportional to the speed of the rotation is generated and sent to the anti-lock brake control module through a twisted cable and shielded wiring harness.

Front

The front anti-lock brake sensors are non-adjustable. The front anti-lock brake sensors and the front anti-lock brake sensor indicators are replaced separately.

The front anti-lock brake sensors are attached to the front wheel spindles (3105). The front anti-lock brake sensor indicators are pressed onto the wheel hubs (1104).

Rear

The rear anti-lock brake sensor is located on the rear axle housing. The rear anti-lock brake sensor indicator is located on the differential case.

G-Switch

The G-switch is used on 4x4 vehicles only. When driven in the 4-wheel drive mode all four wheels are mechanically linked and a situation could arise in which one wheel locks up and causes all four wheels to lock up and skid. The speed sensors would indicate the vehicle speed as zero. Without the G-switch, the anti-lock brake control module would have no data to compare and would react as if the vehicle were stopped when in fact it is moving.

The G-switch detects and signals the anti-lock brake control module whether or not the vehicle is moving.


In the wiring schematics, there is a call-out on the front sensors that says,

A variable reluctance sensor and toothed speed indicator ring used to determine wheel speed. As ring teeth pass by reluctance sensor, a pulsing voltage signal is generated and sent to 4wabs module. Voltage pulses are directly proportional to rotational wheel speed.

Just because you're getting continuity through them doesn't mean they're sending the proper signals. What you would need to see is the signal from both wheel sensors on an oscilliscope while both wheels are rotating at the same speed. The pulse wave-height will not necessarily be the same, but should be the same wavelength at the same speed. If they're not, the module thinks one wheel is turning faster or slower than the other.

Does that help?

-Joe

 

[Eneurb]

Wheel speed sensors on 3rd gen. without traction control can be tested with an ohm meter, but there is no spec published that I can find... Seeing that the resistance in your front sensors are almost the same, I wouldn't suspect a problem. The rear sensor in 3rd gen is the same as 2nd gen, so that looks okay. The best way to check the sensor is to monitor the AC voltage while spinning all the wheels at as close to the same speed as you can.

 

[sacomstock]

Does that help?

-Joe

Yes it does, thank you for taking the time to explain that. It's off to ford I go!

-Steve