Rear Wheel Speed Sensor

[Gen5RangerPegasus]

I have a question for anyone who has a 19-23 Ford Ranger.

I have a ABS/Trac light come on intermittently. Every time I turn off the truck and drive a short distance it goes off and will come back on here and there. Sometimes not at all. I plugged into the OB2 awhile ago and found I had a RR wheel speed sensor that is misreading etc. When I pulled the sensor it appeared damaged and has diff lube on it. I have no external leaks. I know this sensor is my culprit. I attempted to replace it but light stayed on without going off at that point and I am assuming it was because of the fluid in the carrier tube. When I pulled the new sensor out it was like I dipped it in fluid. Needless to say I put the old sensor back in and got my intermittent back.

Here is my question. Is the differntial overfilled or is the seal failing? If the seal was failing would it not leak externally and Isn't the sensor behind the seal inside the tube?

I know I can check the vent tube, which I have not done yet. Thoughts?

Let's Talk.

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[RangerBill]

I have a question for anyone who has a 19-23 Ford Ranger.

I have a ABS/Trac light come on intermittently. Every time I turn off the truck and drive a short distance it goes off and will come back on here and there. Sometimes not at all. I plugged into the OB2 awhile ago and found I had a RR wheel speed sensor that is misreading etc. When I pulled the sensor it appeared damaged and has diff lube on it. I have no external leaks. I know this sensor is my culprit. I attempted to replace it but light stayed on without going off at that point and I am assuming it was because of the fluid in the carrier tube. When I pulled the new sensor out it was like I dipped it in fluid. Needless to say I put the old sensor back in and got my intermittent back.

Here is my question. Is the differntial overfilled or is the seal failing? If the seal was failing would it not leak externally and Isn't the sensor behind the seal inside the tube?

I know I can check the vent tube, which I have not done yet. Thoughts?

Let's Talk.

Was the new sensor a OEM Ford part? If not, I would only use a Ford sensor as others have had issues with aftermarket wheel speed sensors. The axle seal is leaking if you have oil on the sensor and will need to be replaced.

 

[Gen5RangerPegasus]

Aftermarket.

 

[airline tech]

To clear this up - yes its normal to have oil on the sensor, it lives in the oil supply gallery for the bearing.
What needs inspected - is the encoder (tone ring) for metal shavings or debris build up that is being pushed down the tube from the gear sets, rotate the axle and visually look down the sensor hole and inspect the encoder ring.

Yes - it has been noted that some aftermarket sensors, also will generate codes and the conclusion I have come to for the reason is:

The ABS Module is highly sensitive to the - (High-Low) pulsed signal being generated and the signal quality of that signal is very important - so how accurately the sensor is reporting the transitions of the spinning encoder.

1. Frequency = How fast the encoder is spinning

2. Signal = How accurately the sensor is communicating the transitions (High-Low) pulses, I think this is where the Aftermarkets are having the issue and the ABS Module does not accept the signal as believable (its not accurate enough) for the sensitive ABS Module and I think that since the wheel speed sensors tie into other functions (Can Bus) signal driven - Traction Contral - Hill Start Assist and AEB Etc, I think this adds to the sensitivity issue
The signal is generated by the missing tooth (spacing) on the encoder wheel, if there is debris build up on the teeth it can generate a false signal
The signal itself is a magnetic field - so over time the encoder can attract metal debris to it from the gear sets (shavings etc)


So not only the quality and accuracy of the sensor, but the length (air gap) of the sensor also factors in - do the aftermarket and ford sensors - match exactly (gap) between the sensor tip and the encoder wheel when its installed, so something as simple as a different thickness of the mounting flange would pull the sensor farther away from the encoder.The Aftermarket issue is just my theory on why they do not work correctly on the 5G Ranger a true test would be - get the 2 side by side and note the differences and then live data monitor or even better lab scope the frequency between a new or known good sensor to the aftermarket sensor and note how much of a signal difference - that is being reported, since this is what the ABS Module is flagging

Plus we need to factor in - poor connections between the sensor connector and the ABS Module

Now for this specific issue - Damaged Sensor Tip

This can be caused by either issue

1. Bad Bearing or not normal axle play, allowing the encoder wheel to contact the sensor tip.

2. Gear sets - metal shavings caught up in the encoder wheel and the metal shavings hit the sensor tip.

A. Get the wheel off the ground and shake and pull on the axle, any major play noted.
B Drain the differential fluid and check for abnormal metal debris

 

[Gen5RangerPegasus]

It's normal to have "oil" or "diff fluid/bearing fluid" on the sensor?

So what I am gathering is that my assumption is correct - the sensor lives behind the axle seal, recieves lubrication from the differntial fluid at the gear housing, and that it travels down the carrier axle tubes. I have no external leaks and I have checked the play in both of my rear wheels.

When I have time (next day or two) I will pull the sensor and take a picture of it. I don't know if I will be able to get a good look at the tone ring. That was what I was suspecting may have been damage as I did have grey discoloration and an abnormal amount of fluid build up on the wheel speed sensor. When I took it out and cleaned it, my thought was that the shavings and build up of fluid on the sensor have degraded it's integrity. Using an aftermarket sensor (too cut costs) did not help me find a solution. However, I do not want to throw good parts at this truck and not fix the causation of the failing sensor. I am not sure if a small amount of shavings is normal or not on a truck with 100k on it.

I was a technician by trade and went to an automotive technical school before I switched careers, so I have a little know how. I wanted to get some input on this design and to help determine if I need to order two new rear axles with bearings since they are sold as an assembly. I am looking to put a locker of limited slip differential in the rear, and I was considering that if I am going to rebuild the entire rear end that I should do it when I buy the replacement parts. In the meantime I do want to get rid of the ABS trouble code symptom. With your advice I can check the tone ring for damage, and buy a new OEM sensor. Now that I think about it I do recall the flange size being a difference on many aftermarket parts creating an air gap as you have mentioned. Pretty common I would say.

 

[Gen5RangerPegasus]

Update on my wheel speed sensor. I attempted to replace tbe sensor with a new OEM one. The intermittent actions went away but ultimately the problem still exists and in fact my truck finally threw a code. I will post photos. Turns out the tone will might have some mechanical issues so replacing the axle assembly would be the fix.

 

[airline tech]

Before I would condem the axle - pull the sensor and inspect the mounting hole (looking down) at the encoder while rotating the axle - check for debris and damaged teeth (if appears good) then check wiring from (ABS Module Connector to RR Wheel Speed Sensor) (Ohm Them Out) and pay special attention to the RR connector for wire pin damage - if high resistance then move to Inline Connectors C408 and C421

 

[Gen5RangerPegasus]

Before I would condem the axle - pull the sensor and inspect the mounting hole (looking down) at the encoder while rotating the axle - check for debris and damaged teeth (if appears good) then check wiring from (ABS Module Connector to RR Wheel Speed Sensor) (Ohm Them Out) and pay special attention to the RR connector for wire pin damage - if high resistance then move to Inline Connectors C408 and C421

There is a known TSB for my symptoms.

https://www.go-parts.com/garage/abs-wheel-speed-sensor-ford-ranger-ford-bronco-2019-2026

 

[airline tech]

Yes - its common as reported on this forum, but the TSB only references the 2021 - with these specific build dates noted below
It appears the (Rears) are the most reported -here
As of now, my sensors have not triggered any faults - YET

For a single sensor fault its one of the following
1. Bad Sensor
2.Encoder - has accumulated debris - from the differential, which oil supply carried it to the encoder (tone ring) as the encoder sits (Inboard) of the axle seal
3. Bad (Axle) bearing causing the encoder to be damaged (teeth) or throws the encoder out of sync with the sensor (Gap - for accurate reading)
4. Bad Wiring and or Connector (Corrosion) - there is one (inline) connector C408 that has history of water egress (and corroding the pins)

Since after replacing the sensor - and the connection was disturbed, now a deeper code set leaning towards a (Dead Sensor) - requires a deeper look into the issue

Technical Service Bulletin
SSM 50296 2021 Ford Ranger / Ford Bronco – Illuminated ABS Warning Indicator Lamp With DTCs C003A, C0036, C0037, And/Or C0039 – Built On 15-Jun-2021 And Through 15-Aug-2021

Some 2021 Ford Ranger and Ford Bronco vehicles built on 15-Jun-2021 and through 15-Aug-2021 may exhibit an illuminated anti-lock brake system (ABS) warning indicator lamp with diagnostic trouble codes (DTC) C003A, C0036, C0037, and/or C0039 stored in the ABS control module. This may be due to damage or movement of the ABS tone ring on the rear axle. Remove the ABS sensor and inspect the rear ABS tone ring for damage or movement from its original position. If movement or damage has occurred, refer to Workshop Manual (WSM), Section 205-02 to complete the service procedure for axle shaft replacement. If no movement has occurred, refer to WSM, Section 206-09 for normal diagnostics.

 

[Gen5RangerPegasus]

Yes - its common as reported on this forum, but the TSB only references the 2021 - with these specific build dates noted below
It appears the (Rears) are the most reported -here
As of now, my sensors have not triggered any faults - YET

For a single sensor fault its one of the following
1. Bad Sensor
2.Encoder - has accumulated debris - from the differential, which oil supply carried it to the encoder (tone ring) as the encoder sits (Inboard) of the axle seal
3. Bad (Axle) bearing causing the encoder to be damaged (teeth) or throws the encoder out of sync with the sensor (Gap - for accurate reading)
4. Bad Wiring and or Connector (Corrosion) - there is one (inline) connector C408 that has history of water egress (and corroding the pins)

Since after replacing the sensor - and the connection was disturbed, now a deeper code set leaning towards a (Dead Sensor) - requires a deeper look into the issue

Technical Service Bulletin
SSM 50296 2021 Ford Ranger / Ford Bronco – Illuminated ABS Warning Indicator Lamp With DTCs C003A, C0036, C0037, And/Or C0039 – Built On 15-Jun-2021 And Through 15-Aug-2021

Some 2021 Ford Ranger and Ford Bronco vehicles built on 15-Jun-2021 and through 15-Aug-2021 may exhibit an illuminated anti-lock brake system (ABS) warning indicator lamp with diagnostic trouble codes (DTC) C003A, C0036, C0037, and/or C0039 stored in the ABS control module. This may be due to damage or movement of the ABS tone ring on the rear axle. Remove the ABS sensor and inspect the rear ABS tone ring for damage or movement from its original position. If movement or damage has occurred, refer to Workshop Manual (WSM), Section 205-02 to complete the service procedure for axle shaft replacement. If no movement has occurred, refer to WSM, Section 206-09 for normal diagnostics.

The sensor is not "dead". I posted a picture of all the codes. My symptoms point to a bad tone wheel. The truck can drive symptom free for hours. Usually once a trip it will trigger and then reset. My guess is the tone wheel is slipping. I have already inspected the harness, which also is attatched to the locker if you have one, replaced the sensor, and inspected for wheel bearing play. I am almost certain the tone wheel is bad.

 

[Gen5RangerPegasus]

The sensor is not "dead". I posted a picture of all the codes. My symptoms point to a bad tone wheel. The truck can drive symptom free for hours. Usually once a trip it will trigger and then reset. My guess is the tone wheel is slipping. I have already inspected the harness, which also is attatched to the locker if you have one, replaced the sensor, and inspected for wheel bearing play. I am almost certain the tone wheel is bad.

Not to throw parts at this, but I needed to replace the sensor because the other one was physically damaged as mentioned earlier. The speedometer can drop and then reset. Most of the time it will trigger warning lights and wont regain a reading once the computer recognizes the fault. The fact the DTC is not present all the time, the condition is as persistent as it is, and the way it happens points to the tone wheel slipping on the axle. It's hard to describe the symptom as I am driving. I almost drive to gingerly so I don't piss off the rear end . It most certainly is not a loose or corded connection causing this issue. I do appreciate the feedback!

 

[RangerBill]

You mentioned having metal shavings" on the old sensor. What was the source of the shavings? If you still have shavings on the new sensor, that would be the cause of your ongoing codes. Did you use a Ford OEM sensor?

 

[airline tech]

Most likely (yes) its going to be (Encoder) related suspect (debris) on the teeth , but a poor connection can trigger the exact same faults
Causing dropout of the signal - which all 4 codes are referring
Since you inspected (C421) - did you also check C408 - C408 is known (historically) to have water egress into the connector, resulting in corroded pins.
With (2ea) sensor replacements - we know the sensor is good - I was stating (Sensor Dead) meaning the ABS Module is not seeing the signal (Constant).
We can confirm by the codes that the signal is getting lost be it from the encoder or bad connection (signal dropout)

Did you visually inspect the (Encoder) while spinning axle?

C408 - RR Wheel Speed Sensor - Pins 9 & 10

C421 - RR Wheel Speed Sensor - Pin 4 & 5

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