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Rear wheel speed sensor problems

16K views 14 replies 3 participants last post by  bkgeig 
#1 ·
Good day, everyone!
My wife's '05 Sienna LE, FWD started having some problems a few weeks ago after running over something in the road. The Brake and ABS lights were on solid, the tire pressure light was flashing. I took the van to a Ford dealer where my brother works and he hooked up their Snap On scan tool. The right rear wheel speed sensors was dead, no signal at all.

Since the van has over 210K miles on it, I decided to replace the entire bearing hub assembly, rather than just the sensor. It was rusted in there pretty good, but I did finally get the old one out. Afterwards, the lights were still on for a while, ~10 miles or so, then they went off briefly, then they were back on again. Do I need to have the codes cleared, or will they eventually clear after driving a while longer?

I inspected the speed sensor harness from the sensor back up to where it goes thru a grommet and into the inside of the van. I did not see any obvious signs of damage. Is the harness serviceable where I can just replace it? Is there a connector inside the van and if so, how do I access it? Thanks and have a good day!
 
#2 ·
You're one of the few people who have access to a relative who works at a dealer and uses probably a $10k snap on scan tool. Why wouldn't you ask him to hook it back up? He can watch the live data from each wheel sensor and read abs codes, etc.


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#3 ·
The dealer he works at is ~45 minute drive away. I could take it back to the dealer, but would save some time if it would just clear on it's own by driving it.

I suspect that the wires in the harness might be damaged from the chunk of metal that she drove over. She said it was stuck near the right rear tire, she had my son pull it out, so I didn't see how exactly it was wedged in there. It was a decent sized chunk of steel, about 12" long and looked like part of someones inner fender or bent up piece of floor pan.
 
#4 ·
I'm chasing the exact same problem right now. ABS and Brake lights have been on for months. You can clear the codes yourself and it's not too hard to do. Just need a paper clip between two of the connectors in the OBD port. You'll also be able to read the error codes. Not as user-friendly as a dedicated reader, but it works. Take a look in the factory service manual posted here.
 
#5 · (Edited)
With an ordinary volt meter you could unplug the sensor and make sure you are getting good power and ground on the wires coming from the ABS computer with the key on. This is to verify wiring. You could even have someone wiggle them while checking too.

You could also check ohms on the new sensor and compare to the other sensor on the left rear (both should be ~ 1.1 K ohms. )
 
#6 ·
Thanks for the info, I will have to check those things later. Should I check for power & ground from the ABS module to the wheel speed sensor? Or should I look for a signal from the sensor back to the module? I found the module pinout in the service manual, looks like pins 4 and 5. The manual says with key ON, spinning the wheel should generate AC voltage.
 
#7 ·
to check voltage output from the sensor you would have to back-probe it and then using an expensive scanner to read the AC sine waves. leave that part to your brother if it comes to it. Just start by confirming wiring and sensor ohms with a $15 meter.
 
#9 ·
Good day, guys!
I checked the van a little last night, the weather was not cooperating, so I was limited on time and daylight. I tried the paper clip trick to get the ABS codes, code 33 came up, which is for the right rear wheel speed sensor. I unplugged the connector from the new sensor, I only got ~4 volts on the harness. I am not sure if this is normal or not.

I did not try to check the signal directly at the ABS module, I didn't have time to remove the air box and other stuff that was in the way. I did find out that another of my brothers that lives closer to me has a good OBD scan tool that also does ABS codes. Going to try hooking his scan tool up to clear the code and see what happens. I will update you later with results. Thanks and have a good one!
 
#11 ·
I unplugged the connector from the new sensor, I only got ~4 volts on the harness. I am not sure if this is normal or not.
The fact that you got any voltage at all means neither the power or the ground wire were cut open. But, it is another reason I suggested having someone wiggle while you're testing just to test the wiring further. You can also compare voltage with the other side. I got 3 VDC on mine.

Other thoughts maybe that the new sensor is bad (not reading ~ 1.1K ohms), sensor not mounted flush, new hub assembly doesn't not have the same amount of teeth, or new hub is not torque'd to spec.
 
#10 ·
Yeah, getting at the ABS module is a pain. Last time I followed the diagnostics in the FSM, it indicated that I needed to change the module, which costs like $1500! That's why I've just lived with the ABS and Brake lights on for the last months.

I'm not sure what the voltage should be at the connector. In my Geo Metro and F250 I think it's usually about 5 volts. You might check a connector that isn't throwing a code to see what the voltage is there.

For kicks, I ohmed a spare hub I have lying around that I picked up at a salvage yard. It read just over 1.1 k ohms.

Brian
 
#12 ·
UPDATE: I borrowed a good scan tool and cleared the ABS code. The lights come and go, so must be something intermittent. I agree that the wires are not completely broken, but they could still be damaged and lead to the intermittent issues.

I need to play around with the wires to see when the voltage disappears or changes. One thing that I just confirmed, my wife ran over something in the road and a large peice of metal got stuck in that wheel well. It was a piece of sheet metal, about 12" by 5 ", my son had to pull it out of the wheel well for my wife. Does anyone know if the rear ABS speed senso harness has a connector to replace it? Ir do I need to scavenge junk yards and cut out a section to splice onto my van? Thanks and have a good one!
 
#13 · (Edited)
looks like rock auto has the last stretch of the harness for sale.

http://www.rockauto.com/en/catalog/...onnector,abs+wheel+speed+sensor+connector,762

I'd make sure this part does actually exist on the van and try to remove it first before buying.

otherwise per the wiring diagrams found on the FSM, the next junction connector is all the way up behind the glove box. I unplugged the top half of the junction and got the same voltage I was getting at the wheel, so it has to be the right pair of wires.

Heres mine:
https://goo.gl/photos/y53bVCoqHPgS14Mr6
 
#14 ·
Finally got around the checking the sensors on our 2006. Here are some suggestions based on my experience. In the rear, I found it helpful to spray some silicone lubricant on the connections and let it soak in for a minute. They then pulled apart easily. Without the lube, I was struggling to separate them. After testing the connections I cleaned them with QD Electronic Cleaner before reassembling. I really had to push hard to get the connections to snap back together but they did finally lock.

It's difficult to probe the rear sensor, so I used an extra connector from the salvage yard to make a wire extension:


Both rear connectors showed 4 volts. The RR sensor ohmed at 1.23 and the LR at 1.192. The right seems a bit high but still within spec.

Onto the front, which are quite different than the rear. I unbolted them, cleaned the sensor with electrical cleaner, blew out the cavity it fits into, and then reinstalled:




The lights on the dash were still on. Since we needed to take the van into the stealership for 2 recalls, I asked them to pull the codes. They confirmed that the ABS module is bad. I plan to order a rebuild from https://modulemaster.com/rebuilds/shop/brakes/abs-modules/sumitomo/. I'll try to remember to follow up whether this finally fixes the problem.

The dealership also quote me about $9,000 in additional repairs! And told me not to drive the van until the brakes are fixed and the radiator replaced. It's true that the ABS doesn't work, and hasn't worked for the last year, but the brakes themselves still function. I also need to address a small leak in the radiator soon. At least now I have a list of things to work on over the next year.
 
#15 ·
I remembered that I had pulled an abs "distribution block" (if that's what it's called) at the junkyard last year. I pulled it out of storage and found that the abs control module was still attached. So I replaced the module in the van with the used one. "ABS" and "Brake" lights are no longer on! Not bad for a couple hours labor and about $70 at the junkyard.

If you try this, you might want to know that Toyota definitely did not design the abs module to be replaced with the block still in the van. The bottom bolts are impossible to see and very difficult to access. A combination of several different hex wrenches and a lot patience was required. Of course, the air box needs to come out first and the battery should be disconnected.
 
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