ABS Sensor or worse?

Hi All,

Longtime lurker, new member. Thanks for the earlier help! We own a 2008 Touring bought from the original owner in 2011 or so, now with 360k kM (225K miles) which has been mostly great, only serious problems being the Inverter cooling system pump which has failed twice over the years. We're on our 4th 12V battery and replaced the traction battery two years ago. We live in Ontario, Canada but winter in southern Mexico where the car is now, in the middle of its third trip south, hopefully headed back north in a month or so.

Last summer up north it needed a new driver's side front bearing which was done at a local garage. After that the ABS/VSC/! lights came on and would go on and off sporadically. Never spotted a pattern. After consulting here and having the bearing garage look at it it seemed the LF ABS sensor was the problem. Replaced it, problem continued. Other than the lights on the dash there seemed to be no major effects. I got an OBD cable and a copy of Techstream working on an old laptop and confirmed that it seemed to that ABS sensor was the problem. Ran out of time up north and punted the problem down the road, not too worried.

Our gas mileage was about 10% worse than usual up north and has been getting worse and worse down here. This is mostly shortish trips under 100kph with the AC working hard but we're now burning like 1.5x the gas we used to. That sucks but isn't the end of the world, but I'm a bit concerned that the ABS sensor failure has led to the braking system working overtime leading to the bad mileage and rapid wear on the front brakes and the actuator, which would be hard to replace down here. Driving wise I haven't had any real issues and haven't heard the actuator system making weird noises, or maybe I'm used to them? Probably unrelated but with the bad roads and speed bumps here the strut assemblies in the front need replacing and the undercarriage and frame surfaces just behind the front wheels hit speed bumps pretty firmly some times.

So my questions:
1) Is there something that the garage could have done wrong in the bearing replacement that started all this, like a misalignment of the ABS sensor and the teeth of the gear it senses, that has led to the original and replacement ABS sensor both failing to work consistently. Something I can fix?

2) Is there some way to easily figure out the problem Dr Prius or Techstream? I have both here though neither is bulletproof in operation.

3) If I choose to drive the 5000 km north as is with the poor fuel mileage are we in mortal danger?

4) Is there a thread on here that covers this topic exhaustively that I have not yet found? If so, thanks for the referral.

Thanks much for any assistance or links.

 

Thanks for the ideas. Aegean, I replaced the FL ABS sensor myself, the wiring did not seemed stressed, and the fact that the symptoms did not change with the new sensor makes me suspect the sensor itself isn't the problem. The HV replacement battery was OEM from Toyota so I don't suspect it though I will run Dr Prius one day soon.

Brian I think you are right that there is/was something wrong caused by the bearing replacement but can't tell what. I do see regenerative braking / HV battery charging happening on the Energy screen so that doesn't seem to be it.

I got techstream working today and the codes were the same as last fall:
C0205 Front Speed Sensor LH Circuit
C1236 Foreign object is Attached on Tip of Front Speed Sensor LH

Confirming the problem is related to that sensor.

I jacked it up and put new brake pads on the right and then left. The old ones were down to maybe 30% but I had new ones handy and the disks seemed ok. Not sure if we ever replaced them before, even after 360k km. Took a look at the sensor and the gear inside. Replaced the LF pads and the sensor situation looked similar. I did scrape the mounting surface and filed the seating end of the sensor a bit to hopefully get a fraction of .001 inches closer to the gear.

I had my wife drive out to the highway, looking with techstream at the wheel speed values and they seemed fine. After a few minutes the three dash lights ABS VSC Brake came on again and I found in techstream how to clear them and did, the lights went out but don't know if they will return as they have so often.

I'm encouraged that 1) no worse or new trouble codes came up 2) the brakes, regeneration, etc seem to work normally even with the bad sensor problem and 3) I can get techstream running even while the car moves, to clear codes, possibly turn off traction control, and read the wheel speeds (and so much else) on the go. I'm feeling OK about the Actuator which seems to behave normally.

Not clear why the mileage is bad but maybe it will get better on highways north. If gas in the US stays cheap another 6 weeks it won't be too big an expense.

Thanks again, and I welcome any more advice / speculation / commiseration.

 

Thanks for the ideas. Aegean, I replaced the FL ABS sensor myself, the wiring did not seemed stressed, and the fact that the symptoms did not change with the new sensor makes me suspect the sensor itself isn't the problem. The HV replacement battery was OEM from Toyota so I don't suspect it though I will run Dr Prius one day soon.

Brian I think you are right that there is/was something wrong caused by the bearing replacement but can't tell what. I do see regenerative braking / HV battery charging happening on the Energy screen so that doesn't seem to be it.

I got techstream working today and the codes were the same as last fall:
C0205 Front Speed Sensor LH Circuit
C1236 Foreign object is Attached on Tip of Front Speed Sensor LH

Confirming the problem is related to that sensor.

I jacked it up and put new brake pads on the right and then left. The old ones were down to maybe 30% but I had new ones handy and the disks seemed ok. Not sure if we ever replaced them before, even after 360k km. Took a look at the sensor and the gear inside. Replaced the LF pads and the sensor situation looked similar. I did scrape the mounting surface and filed the seating end of the sensor a bit to hopefully get a fraction of .001 inches closer to the gear.

I had my wife drive out to the highway, looking with techstream at the wheel speed values and they seemed fine. After a few minutes the three dash lights (ABS VSC Brake!) came on again and I found in techstream how to clear them and did. The lights went out but don't know if they will return as they have so often.

I'm encouraged that 1) no worse or new trouble codes came up 2) the brakes, regeneration, etc seem to work normally even with the bad sensor problem and 3) I can get techstream running even while the car moves, to clear codes, possibly turn off traction control, and read the wheel speeds (and so much else) on the go. I'm feeling OK about the Actuator which seems to behave normally.

Not clear why the mileage is bad but maybe it will get better on highways north. If gas in the US stays cheap another 6 weeks it won't be too big an expense.

Thanks again, and I welcome any more advice / speculation / commiseration.