ABS Light on

[bwenny247]

Hey guys, didn't know whether to put this in the electrical or mechanical forum but here goes.

My ABS light is constantly on. I used the HPPIII to diagnose a C0221 code which is " Right Front Wheel Speed Sensor Circuit Open" so i crawled under and everything seems to be hooked up and fine.
Anybody have this code before, if so what did you do? maybe replace the speed sensor?

Thanks for the help!
-Ben

[F9K9]

I hope this gives you a starting point.

Step
Action
Values
Yes
No

Schematic Reference: ABS Schematics

Connector End View Reference: ABS Connector End Views


Important
If DTC C0229 is set, diagnose DTC C0229 before diagnosing any other wheel speed sensor DTCs.


1
Did you perform the ABS Diagnostic System Check?
--
Go to Step 2
Go to Diagnostic System Check - ABS

2
Use a scan tool in order to clear the DTCs.
Operate the vehicle at a speed greater than the specified value.
Does the DTC set?
19 km/h (12 mph)
Go to Step 3
Go to Diagnostic Aids

3
Turn OFF the ignition.
Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
Disconnect the wheel speed sensor connector.
Use a DMM in order to measure the resistance across the wheel speed sensor.
Does the resistance measure within the specified range?
700-10,000 ohms
Go to Step 4
Go to Step 8

4
Spin the wheel by hand as fast as possible.
Use a DMM in order to measure the AC voltage across the wheel speed sensor as the wheel spins.
Does the AC voltage measure greater than the specified value?
100 mV
Go to Step 5
Go to Step 8

5
Inspect for poor connections at the harness connector of the wheel speed sensor. Refer to Testing for Intermittent and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 10
Go to Step 6

6
Disconnect the EBCM harness connector.
Test the wheel speed sensor circuits for the following:
An open
A short to ground
A short to voltage
Shorted together
Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 10
Go to Step 7

7
Inspect for poor connections at the harness connector for the EBCM. Refer to Testing for Intermittent and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 10
Go to Step 9

8
Replace the wheel speed sensor. Refer to Wheel Speed Sensor Replacement .

Did you complete the replacement?
--
Go to Step 10
--

9

Important
Use the scan tool in order to perform the Tire Size Calibration procedure.


Replace the EBCM. Refer to Electronic Brake Control Module (EBCM) Replacement .

Did you complete the replacement?
--
Go to Step 10
--

10
Use the scan tool in order to clear the DTCs.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC reset?
--
Go to Step 2
System OK

[HenryJ]

OK, now since you may not have a $4000 scan tool here is what you might look at.

First thing is first. Make darn sure that you do have a problem. You have read the code, now clear it and see if it recurs.
If the light does come back on , have it read again to confirm the same code.
If it does come back with the same code , if you are a "hands on" type, and have a few tools, this is the "backyard mechanics method" :
You are a detective-

Gather up and interrogate the usual suspects.

The first "known offender" is that miserable fiend the wheel bearing. He can be a hard case so we will check out some of the easier suspects first.

#1 cables and connections. Just like a good investigator "tail'em", or follow them. Check every lead and connection. When you find a connection take it apart and inspect the terminals, add a little dielectric silicone, and plug it back together. Trace it far enough to check for signs of damage like cuts, pinched or smashed, burns, etc.
This will require you to jack up the truck and remove the wheel/tire.

#2 If all that yields no culprit, then proceed to the hard case.

On a full size I would inspect the sensor first, but it may be necessary to pull the hub, so we'll check the bearing first.

You need to be able to jack up the wheel from the lower a-arm as close to the wheel as possible. A small bottle jack or floor jack should do the job. This keeps the lower ball joint loaded. Park close to a stationary fixed object. A pole or post works well since you will have room to get up beside it. If a wall is all you have, you may need to crawl under a little to take measurements. Now attach a piece of masking tape between the post/wall and the outermost part of your wheel. push in on the top of the wheel and make the tape tight. Now when you pull back on the wheel, does the tape get loose? Is there movement? Don't pull so hard as to flex the a-arm bushings, or upper ball joint. We are just trying to determine if there is any free play in the bearing.
This is professionally done using a stand and dial indicator just above the bolt circle on the wheel. Maximum permissible movement is .005 inch.
If you find some slack, it is likely that you do have a bad wheel bearing, but proceed to the next layer of inspection.

This gets a little more involved. We need to check that sensor. This requires you to remove the wheel again. Remove the brake caliper, remove the rotor.

This is the point at which you can remove the sensor on a fullsize, but it looks as if our shield may interfere, so we are going to have to remove the hub, then remove the sensor mounting clips, disconnect the electrical connection, remove the mounting screw. Carefully pull it straight out of the hub, don't pry or damage it.
Inspect the sensor for damage . cracks, or metal filings from a failing bearing. Look into the bore from which it was removed to check for signs of contamination , or metal.

This is no easy task, but it can all be done. When I started writing this post it all seemed so simple, after writing this it starts to sound a little "involved"
If you are nervous check with an alignment shop. Have them check your wheel bearing. They can put it "on the rack" and see the bearing runout.

If all of this fails to find a suspect, you may indeed have to test that sensor. Weigh the cost of a new sensor, to the cost of having a dealer diagnose the sensor. If everything else looks real good you could gamble and try replacing the sensor. I don't know the cost , and I really don't know the failure rate of the sensors. I doubt they fail very often. I might even try a used one, or swap sides if that is an option.
A new wheel bearing may come with a sensor, so this is something to consider as well. It is tough, but you may possibly convict the wrong suspect with out careful consideration.
Use your best judgement.

[quickbiker]

When that happened to me, my wheel hub bearing was on it's way to shot. I got a replacement from Napa which includes the sensor for about $200.