DR. A Tech Alert- Rear wheel speed sensors

abittenbinder

Doktor A (864-623-9110)
The rear wheel speed sensor system, sensors and tone wheel, provide critical information not only to the ABS/ESP/ASR systems, but also to the TCM.

The TCM uses this rear speed signal to calculate transmission output shaft speed (The TCM is programmed with the appropriate rear axle ratio).

Transmission output shaft speed is needed to determine slippage, gear selection errors, ratio errors, etc.

Loss of both rear sensor signals or a mismatch of 2 rear signals can result in severe transmission symptoms as well as ABS/ESP/ASR symptoms.

Loss of 1 rear sensor signals can result in sporadic transmission anomalies as well as ABS/ESP/ASR malfunction.

Unlike the front wheel speed sensor tone wheels, the rear tone wheels are heavily exposed to contamination debris ( corrosion fallout, disintegrating hand brake shoe components) which can damage the original, thin stamped steel, tone wheel and wheel sensor face alike.

Also, unlike the front wheel speed sensor system, the rear sensors (and tone wheel face and gap) are not visible until the brake caliper and brake rotor are removed. The top hand brake shoe then needs to be carefully pried forward to inspect the sensor to tone wheel gap and the tone wheel condition.

In rust belt zones, the rear wheel speed sensors can readily seize in their axle mounting bores. Attempting to adjust the speed sensor gaps should NEVER be done without visual inspection and confirmation of gap during adjustment.

The originally installed rear tone wheels are quite thin and fragile. Their 45 degree tone face makes them even more vulnerable to damage.

Original design rear tone wheel, Dodge part# 5134641AA (MBenz # A 902 357 06 51) can now be ordered as a improved, much stronger cast steel component. Dodge part# 5134640AA (MBenz # A 902 357 02 51)

Refer to the factory workshop manual's 'disassembly of rear axle shafts', for details on replacement of damaged rear tone wheels.

Doktor A
 

schwarzeradler

New member
Thanks for the info! The "disassembly of rear axle shafts" is not really what I was hoping to hear (I don't have an auto shop). I've looked at that portion of the manual many times now trying to see where the tone ring fits in. The manual I have doesn't mention it in the procedures for the single rear wheel axle disassembly or reassembly. It appears that it may need to be completely taken apart, bearings and all, to access the tone rings. I.E - need to have big presses and specialized tools. Is this true, or can it be accessed with a little less disassembly?

Thanks, also, for the new part number...Berry's has that one, but not the old number.
 
I had a similar problem where the DAD indicated a bad right rear speed sensor. Purchased a new one, and me a tool to pull the old one. Upon removing the wheel and the brake caliber, I could see extensive debris on the outside of the sensor. The sensor is magnetic! When I used my puller, the sensor came right out (notice that I did NOT cut the cable - I wanted to see first what was wrong) . I cleaned it and tested it and it checked out good. I blew out the all the debris and re-installed the sensor. It works just fine! I cleared all faults and had no problems since. I returned the new sensor to the dealer ship for a refund.

Sven
 
The ABS Sensor has a diameter of 16mm. As I wrote before it is magnetic and will sense metal passing by. I had my DAD connected and on "Live Data" for the ABS program. If you take anything metallic and move it past the sensor you will get a reading, if the sensor is working okay. When I re-installed mine and turned the axle, I got a reading immediately, which matched the other rear wheel.

I believe that the debris from metallic brake pads got build up around the sensor and did not allow it to read properly.

Before I did all this I check the Ohm reading on the plug at the ABS Module. Dr. A helped me that a great deal and lead me on the right path to figure this thing out. So if your sensor reads about 1.8 ohms, it should be good. if it is, try cleaning with compressed air from the outside. Just remove the wheel and you will understand.

So a big thanks to him as well!!!!!

Let me know if my explanation made any sense. To convert to inches, just multiply the numbers by 25.4.

Good Luck.

Sven
 

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abittenbinder

Doktor A (864-623-9110)
T It appears that it may need to be completely taken apart, bearings and all, to access the tone rings. I.E - need to have big presses and specialized tools. Is this true, or can it be accessed with a little less disassembly?
That is true.

And yes, the '02-'06 Sprinters employ inductive speed sensors.

These are magnetic and attract debris, which can include flaking corrosion as well as errant hand brake assembly component fragments. This entrapped debris can then damage the face of the sensor and the tone wheel.

Doktor A
 

schwarzeradler

New member
I've ordered a new tone wheel, however, the "seal kit" part number 05104559AA in the parts list, doesn't seem to exist at Barry's sprinter parts - or on a google search. The service manual seems to stress putting all new seals in when reassembling the axle, which makes sense. Does anyone know of another part number for these seals? Any tips and tricks I should know before tackling this project?

Thanks!
 

220629

Well-known member
I've ordered a new tone wheel,
...
Any tips and tricks I should know before tackling this project?

Thanks!
Since making the comments below I have changed out my rear axle seal and actually viewed the tone ring. There is no way my idea will work.

I have not installed a tone ring in my Sprinter. The rear wheel seals leaking doesn't seem to be a common problem even as our Sprinters get higher mileage. Were I to attempt this DIY I'd be doing what I could to avoid disturbing/disassembly of the rear axle and its pressed in bearing assembly.

If the seal isn't leaking I'd look closely into whether the new part can be modified to split apart and be installed without removing the axle. From what Doktor A and Eric Experience have indicated removing the bearings to remove the seal requires special tools or at least a press and some ingenuity. The tone ring is not that big in diameter so the centrifugal forces on it shouldn't be very great. It should be able to be clamped or wired into place after installed in position? Maybe a litlle JB Weld added for piece of mind?

Again, I have not done this job so these are just suggestions. Good luck. vic
 
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abittenbinder

Doktor A (864-623-9110)
The tone ring is not that big in diameter so the centrifugal forces on it shouldn't be very great. It should be able to be clamped or wired into place after installed in position. Maybe a litlle JB Weld added for piece of mind?
The tone wheel is designed to be an interference (press) fit onto a stepped face of the axle.

Doktor A
 

Andy in NH

New member
Thanks for the notice on the sensor. I though my transmission was getting funky and I KNOW the brakes need work. Sprinter into the shop on Thursday (I have no garage or time :frown:). Fortunately it will be in the capable hands of the famous Carl at Flagship so less worries for me other then the inevitable $$$$.
 

schwarzeradler

New member
It would be nice if the tone wheel could be split or something, but being a press fit, that won't work out. Does anyone have an updated or alternate part number for the "Seal Kit", which is listed as part number 05104559AA? I can't seem to locate it anywhere.

Thanks!
 

220629

Well-known member
It would be nice if the tone wheel could be split or something, but being a press fit, that won't might not work out.
...
Thanks!
Since making the comments below I have changed out my rear axle seal and actually viewed the tone ring. There is no way my idea will work.

DIY is not as limited to methods as would be a dealership, etc. Press fit is still a "close fit" within thousandths. I wouldn't discount another method without looking very carefully for alternatives. It doesn't matter how you make it stay in place, just that it stays there properly aligned. It's not at all like a bearing or gear which would be under higher stresses.

That said, I have not looked at it myself to see if there is even enough room/access to consider alternatives. I did hear a rumor that it may be possible though.


vic

I'll let it go now.:rolleyes:
 
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dbeyer

Member
I was experiencing the following symptoms:

1. minor drive line vibration when in stop and go traffic at speeds less than 4 mph.

2. Brake pedal pulsating between 4 mph and complete stop.

Dad reports

ESP (ABS) F1111 - could not find and reference in code book and no data on forum.
TCM - no codes

Live data for ESP reveled right rear speed sensor stopped reading at 4 MPH and the other 3 sensors read as slow as 1.2 MPH.

I pulled the right rear rotor and found the sensor very dirty. I blew it out with air compressor and electric cleaner. Reassembled and did test drive without success.

Called Doktor A, left message and pulled the left rear rotor to clean the sensor. As I was finishing putting the left rear wheel back on Doktor A called back. I was sharing information with Andy and mentioned the right rear sensor's gap was larger than the left. He suggested I take a wooden dowel and tap the end of the sensor. Andy warned not to do this blind, without removing the rotor and lifting the parking bake shoe to view the gap. Andy also advised if it didn't move not to bang too hard because I would damage the sensor.

This worked perfect 3 light taps and the sensor moved closer to the tone wheel.

Test drive revealed that all symptoms were gone and the DAD ESP live data now reads the right rear sensor consistent with the other sensors. :drink:

Pics are before adjusting gap and after.


Thanks again Doktor A. You rock!

I think it is good idea to clean and inspect the rear sensors every brake job.
 

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abittenbinder

Doktor A (864-623-9110)
I was experiencing the following symptoms:
Brake pedal pulsating between 4 mph and complete stop.

Dad reports ESP (ABS) F1111 - could not find and reference in code book and no data on forum.
TCM - no codes

I think it is good idea to clean and inspect the rear sensors every brake job.
I agree it is a good idea to clean and inspect the rear wheel speed sensors and tone wheels at least during every brake job.

Keep in mind that a wide, mis-adjusted sensor gap is NOT logged as a fault in the ABS/ESP module.

A wide gap results in a very weak or dropped signal at slow speeds which is interpreted as wheel lock. No malfunction of hardware occurring, just a mis-interpretation, hence no fault code.

Doktor A
 

Pilgrim

New member
have an 03 LT showing ABS CEL and AWS lights. Scan showed right rear speed sensor fault. Checked and replaced. That turned off the CEL but still have the ABS and AWS light on. Does that mean I need to rescan to turn off the warning lights or look for another problem.
 

talkinghorse43

Well-known member
have an 03 LT showing ABS CEL and AWS lights. Scan showed right rear speed sensor fault. Checked and replaced. That turned off the CEL but still have the ABS and AWS light on. Does that mean I need to rescan to turn off the warning lights or look for another problem.
I'm guessing they will require a rescan.
 

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