2006 Camry - Intermittent ABS at Low Speed

Maintenance/Repairs
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1

On my 2006 Camry, my ABS comes on intermittently when braking (~5% of the time) and the speed is very slow (5 mph or less). Exact speed is hard to say. I think one of the ABS sensors is misreading. No ABS fault light on dash.
I have an explanation of how to check the sensors for AC voltage when spinning the wheel using a DVM.

  1. Without a lift can I check this under the hood instead of at the wheel? Possibly at the plug into the ABS module.
  2. Someone else on another thread mentioned that their dealership hooked in a monitor and drove around. When I asked my dealership how they would diagnose this, they said they would do the same check as I mentioned above (#1). This would be expensive and since it is intermittent, they might not see anything. Does anyone know if this monitor exists and what it is called?
2

One thing that can cause an intermittent ABS light is a worn wheel bearing.

At high speed, the worn wheel bearing will keep the tone ring aligned with the ABS sensor.

But when the vehicle slows down, the worn wheel bearing can allow the tone ring to become misaligned with the ABS sensor, so the ABS light comes on.

The tone ring on your vehicle is located on the half shaft. The half shaft is supported by the wheel bearing in the steering knuckle. And the steering knuckle is where the ABS sensor is mounted.

Tester

3

A dealership scan tool probably has the capability to test the wheel speed sensors without having to bring out the dvm or an o’scope. That may be what you are referring to by the “monitor”.

If you are going to try it yourself using a dvm, you’ll be at the wheel anyway, making it spin, so wouldn’t it be easier for you in any event to measure at the wheel rather than inside the car?

Below be helpful for some background information.

http://www.agcoauto.com/content/news/p2_articleid/267

4

I don’t know where the connector is on the front wheels and I can’t get under the car without jacking it up to trace the cable. I don’t want to go under with just a jack holding it up. I wanted to do it with 2 people, one under the hood watching the meter and then I could jack up one side and the other person can spin.

It annoys me that the dealership did not mention the scan tool. They wanted to put the car on the lift and test the sensors individually at 1/2 per wheel. So if they ended up doing all 4 wheels it was almost $300. It seems if they could hook up the monitor and let me drive it around for 15 minutes this should be only a small amount of time. Not sure if I should trust this dealership or not.

5

@oceanus

What you are proposing to do is a bad idea for a novice, IMO

You’d have to know exactly what pins to go to at the module, and you’d have to backprobe them, without damage

I don’t know what kind of DMM and leads you have, that’s why I said it’s a bad idea for a novice

The dealership is not going to let YOU drive the car for 15 minutes with THEIR scan tool hooked up. No dealership would let a customer do that. Probably not even if their mechanic was in the car with you. That would open themselves up to all sorts of ugliness, such as you possibly misinterpreting a pid and thinking there’s a problem, when in fact there is none. Or you trying to influence the mechanic in some way

No offense meant, BTW

Can I presume the dealership checked for stored ABS fault codes?

FWIW . . . what you describe are the classic symptoms of a bad wheel speed sensor. And when a wheel speed sensor is bad and behaves in the way yours may be, it doesn’t always generate a stored fault code

Here’s what the dealership probably wanted to do . . .

Hook up the scan tool and check for stored or current ABS codes

Rack the car and spin the wheels while monitoring the signal, probably with a meter. And look for obvious damage . . . such as rat damage . . . to the wiring and/or sensors, while it’s racked

Drive the car with the scan tool hooked up, while monitoring the signals of all 4 corners

Measure resistance of each individual sensor, using the meter

That probably adds up to well over an hour of diagnostic time. With dealer labor rates generally being well over $100 per billed hour, plus tax, I can easily see that adding up to $300

6

They may have that scan tool, and that’s just how the diagnostic test works when using it. The vehicle has to be off the ground enough to allow the wheels to spin freely, right? No getting around that. They charge 1/2 hour per wheel? So 2 hours of work for $300? Seems a little high both on the amount of time needed and the price per hour, but really not unreasonable for a dealership. Especially in a high cost urban area.

From what you say, you know what? I think you’d be better off just letting the dealership do the test and pay them what they charge. I’d probably ask what form of guarantee they offer, for example what if this $300 test doesn’t turn up the problem.
.

7

No offense taken, I appreciate the direct feedback. My dealership/scan tool question came from a post on this forum describing their experience of driving around with the tool. I am a novice with this, but I am a controls engineer with experience with diagnosing electronics and sensor issues. I thought there might be a pinout diagram for the connector. I agree trying to probe it is a bad idea. I also thought the scan tool would generate a log of what sensor tripped making it a quick and easy to target which wheel is the problem.
I will start with the back wheels, hopefully I will get lucky and find the issue there!
Thanks

8

@oceanus

Thanks for the update

Given your profession, I’m sure you have a decent fluke and leads to backprobe terminals without damage, for the purposes of measuring that signal voltage

To measure resistance, you’ll have to measure directly at the sensor, unplugged, or all the way at the module, with it unplugged. I like to measure up front, personally

Backprobing properly will allow you to see the real time values, without opening up the circuit, so to speak. And won’t damage the terminals, if done properly

I just happen to own a 2005 Camry . . . same body style as yours . . . and personally own the factory wiring diagram. The pinouts at the module are different, Japanese-built, versus Kentucky-built. But the wire colors for the sensors are same.

I’ll give you the colors for the sensors, at the module itself

left front yellow is negative, brown is positive

right front black is negative, white is positive

left rear green is negative, red is positive

right rear light blue is negative, pink is positive

Resistances are different, Bosch module, versus Denso module

front sensors, Bosch system, 0.92 - 1.22 kiloohms

rear sensors, Bosch system, 1.3 - 1.6 kiloohms

front sensors, Denso system, 0.6 - 2.5 kiloohms

rear sensors, Denso system, 1.3 - 1.6 kiloohms

If you unplug the connector at the module, you can measure resistance there. You can also measure the voltage signal voltage, if the car’s on jackstands

If you like, I can try to describe the procedure for retrieving fault codes WITHOUT a scan tool.

I’m not that computer savvy, otherwise, I’d scan the pages and post them :frowning:

9

Thank you for the detailed information. Let me Google the fault code without scan tool, maybe someone has written it up already, saving you typing.

10

@oceanus

A bit of advice . . . the method I’m thinking of involves bridging 2 pins on the 16-pin datalink connector inside your car, under the dash, on the left side

If you see any postings showing you bridging 2 pins under the hood, that won’t work. Because that’s for older vehicles. You don’t even have that D-shaped underhood connector

11

It is fixed. Replaced the drivers side front ABS sensor with a new Toyota one. I found a mechanic that connected a computer to the ODB connector and monitored the ABS. We drove around for a few minutes reproducing the conditions that make it occur and that wheel would drop to zero while the other were reading 4 MPH.
We took the wheel off and the tone ring appeared fine, so it seemed like the sensor had to be the culprit and it was.
Mechanic recommended using the Toyota sensor even though it was expensive. He had seen many other issues with the aftermarket sensors.

12

@oceanus

Glad to hear you got it fixed! :star:

13

Yes, good for you to have ti working correctly again. Wheel speed sensors are located where they get a lot of abuse, stuff coming up from the road, so they are pretty common failure items reported here. They’re pretty easy to diagnose if you have a scan tool that includes the wheel speed sensor test function.

14

Mechanic was correct. OEM parts for this type of repair are best. He saved you money in the long run!