How to diagnose which wheel speed sensor is the bad one? | Ford Explorer Forums - Serious Explorations

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How to diagnose which wheel speed sensor is the bad one?

fireball 440

Well-Known Member
Joined
April 3, 2011
Messages
170
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Location
Northern MN
City, State
minnesota
Year, Model & Trim Level
2015 Police Interceptor
My 2005 Explorer with Auto4x4, RSC, & ABS has a bad rear wheel speed sensor. I have them both unplugged so I can drive the vehicle. It is immobile with them connected. This has been fine for the past 6 months but there is 12" of snow forcasted for tonight so I'll need all these systems to work. I looked them up on Rock Auto and go figure RH & LH have different part numbers so not interchangeable.

I need to know how to figure out which side is the bad one. I have an obd2 scan tool but it only connects with the PCM and none of the other modules.
 



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I've searched here several times and started 2 separate threads on what the flashing 4x4 light means and have never found anything. I need to start there but I haven't been able to find any references. It's like Fords best kept secret!
I "almost" bought a NGS2 scanner used last summer but I backed out after telling the wife, now she says I should have bought it. arrrrggggg.
 






The vehicle isn't driveable with both sensors plugged in so monitoring PIDS probably wont be much help. It's like the ABS is fighting the RSC with the sensors plugged in. The more gas you give it, the more it slams on the brakes by itself. I can't even drive it around the block.
FWIW, both front WS sensors I replaced within the last 2 years.
 






contact your parts store and check if they have a scanner that can do ABS, unplug the sensors and drive it there. The codes are stored in the system plus the code for them being open (circuit open/high) You'll probably get a bunch of them,
 






The vehicle isn't driveable with both sensors plugged in so monitoring PIDS probably wont be much help. It's like the ABS is fighting the RSC with the sensors plugged in. The more gas you give it, the more it slams on the brakes by itself. I can't even drive it around the block.
FWIW, both front WS sensors I replaced within the last 2 years.
@fireball 440
You have learned what took me several months to find out: the ABS Module has discretionary power over the PCM to disable the vehicle due to ABS malfunction. Apparently a programmer's thought pertaining to liability issues. My '04 has only one rear wheel sensor, but not too much different from yours with two. The big difficulty I had finding the trouble was the fact that while I got the 4X4 HIGH light flashing, as well as the ABS "ON", and "BRAKE" on, with an occasional wrench icon illuminated, the DTC thrown pointed to the Throttle Body. Turned out the main chip in my ABS Module was not functioning, and it could not throw a warning to that effect. Bottom line is, ABS can and does disable the vehicle by demanding "Forced Limited Power", or limp mode, and can go as far as "Forced Engine Idle", if driven very long without eliminating the warnings.

I learned that when 4X4 HIGH is flashing, 4X4 operation has been overridden; at the same time, so was Speed Control, though I found that out the hard way, by trying it. I'm surprised your vehicle continues to run with the speed sensors unplugged. I struggled with the problems not knowing my OBD-II scanner could NOT read ABS DTCs. Bought one that can, and finally sorted out the issues. As far as isolating the bad sensor: the DTCs will do that for you. A warning: Ford Shop Manual warns against attempting to measure or read wheel speed sensor output with a meter, that doing so will damage the sensor. I bought a used ABS Module, installed it (without the Shop Manual required "configuring"), it works, but the ABS light remains on, throwing a single code: "VIN Mismatch". imp
 






@fireball 440
You have learned what took me several months to find out: the ABS Module has discretionary power over the PCM to disable the vehicle due to ABS malfunction. Apparently a programmer's thought pertaining to liability issues. My '04 has only one rear wheel sensor, but not too much different from yours with two. The big difficulty I had finding the trouble was the fact that while I got the 4X4 HIGH light flashing, as well as the ABS "ON", and "BRAKE" on, with an occasional wrench icon illuminated, the DTC thrown pointed to the Throttle Body. Turned out the main chip in my ABS Module was not functioning, and it could not throw a warning to that effect. Bottom line is, ABS can and does disable the vehicle by demanding "Forced Limited Power", or limp mode, and can go as far as "Forced Engine Idle", if driven very long without eliminating the warnings.

I learned that when 4X4 HIGH is flashing, 4X4 operation has been overridden; at the same time, so was Speed Control, though I found that out the hard way, by trying it. I'm surprised your vehicle continues to run with the speed sensors unplugged. I struggled with the problems not knowing my OBD-II scanner could NOT read ABS DTCs. Bought one that can, and finally sorted out the issues. As far as isolating the bad sensor: the DTCs will do that for you. A warning: Ford Shop Manual warns against attempting to measure or read wheel speed sensor output with a meter, that doing so will damage the sensor. I bought a used ABS Module, installed it (without the Shop Manual required "configuring"), it works, but the ABS light remains on, throwing a single code: "VIN Mismatch". imp
Oh man that sounds like a diagnostic nightmare. I don't know how watching WS on a PID display could damage a sensor, I've done it many times I was a certified Ford technician 1995-2000. If I had a NGS I could do anything to this vehicle that I wanted. I'm stopping down to Auto Value tomorrow morning to use their scanner, but I know I'll get several codes and at least 1 for each of the rear WS. So if I get 2 codes for one side and 1 for the other, could it be a good bet to which one is malfunction? I looked at the tone rings a few months ago and their not cracked or broken. I hate playing the guessing game when I'm one step away from the actual cause.
I also don't like how electronically dependant these Explorers are. I get it though, to be tech advanced. I've had several electrical issues with this Explorer.
 






did you try only unplugging one wheel at a time? I imagine this would muck things up even worse, but I also didn't see where you said that you had tried it.
 






Yes with either one of them disconnected it's a no go, I've driven 10,000 miles with both of them disconnected. Flashing 4x4 light, ABS light on, RSC light on, "Check Advantrac" warning, lights on the entire time.
 






Oh man that sounds like a diagnostic nightmare. I don't know how watching WS on a PID display could damage a sensor, I've done it many times I was a certified Ford technician 1995-2000. If I had a NGS I could do anything to this vehicle that I wanted. I'm stopping down to Auto Value tomorrow morning to use their scanner, but I know I'll get several codes and at least 1 for each of the rear WS. So if I get 2 codes for one side and 1 for the other, could it be a good bet to which one is malfunction? I looked at the tone rings a few months ago and their not cracked or broken. I hate playing the guessing game when I'm one step away from the actual cause.
I also don't like how electronically dependant these Explorers are. I get it though, to be tech advanced. I've had several electrical issues with this Explorer.
@fireball 440
NGS or a World Wide, wouldn't we be set then? I think what they're saying is that applying voltage to the sensor, such as connecting a VOM to read resistance, might damage the sensor. It's possible, I suppose. I attempted to read output of one of the front sensors with car up on jackstands, all wheels turning ion gear, and read a steady-state low voltage, forget what it was. That was after I got a code for that sensor indicating it had a fault.

Not sure about your codes question. It almost sounds like what I had: limp mode being set does not seem likely with just a bad speed sensor. My guess is the ABS Module is a fault, just like mine was. If you gat a "ABS Module Malfunction" code, that will do it. If you get that far into it, I found a place that repairs all faulty modules, if repairable. I sent them mine, not knowing if they were legit, turns out they refunded my payment, main chip was dead in it. Seemed right, the used ABS Module fixed it. If you want their site url, just ask. imp
 






Did you see any TSB's or SSM's about that module? I haven't had oasis access in many years.
 


















Replaced left rear WS sensor, all is good now.
ABS, RSC, & 4x4 lights are now all off and all systems acting normal again.
 






On another note, I replaced the RF wheel bearing (again) this morning. The damn wheel was about ready to fall off! Just replaced it 23 months and 35,000 miles ago!
 












On another note, I replaced the RF wheel bearing (again) this morning. The damn wheel was about ready to fall off! Just replaced it 23 months and 35,000 miles ago!

What junk brand are you using? I'd bet good money it's not SKF, the only brand you should be using.
 






I don't know what brands they are, both fronts are different brands now. The brand that failed with 35K was bought at Auto Value for $145 in December 2014.
 









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Probably. No time to search or wait for parts, gotta take what's available.
 






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