I guys,

I believe the intermittent ABS/AH/TC issue that I've had for the last 2 weeks are due to one of the ABS sensors. Can someone post some pics of those sensors so I can locate them and try to troubleshoot my problem.
Thanks in advance

Greg

 

I believe the wheel speed sensors are integral with the wheel bearing assemblies.

About 2 years ago I had the "Service ABS" and "Service TC" DIC messages; the trouble code indicated that the problem was an intermittent wheel speed sensor reading. A service tech told me that code was almost always caused by the short wiring harness that connects to a connector on the frame & goes out the the sheel speed sensor connector. I took it off, cleaned all the contacts & reassembled & the problem was gone.

The problem recently returned, so I'll try the same fix, or if necessary, change the harness, which is what the tech originally suggested.

Have you checked the DIC code(s)?

 

Yes I checked the codes and cleaned them, here they are :

10 - PCM : NO CODES
28 - TCS : U1301H
40 - BCM : NO CODES
58 - SDM : U1000H U1301H U1040H U1064H
60 - IPC : U1255H
80 - RADIO : U1064H U1016H U1096H
99 - HVAC : NO CODES
A0 - LDCM : B2252H B2282H B2284H U1255H U1064H U1016H U1096H
A1 - RDCM : B2283H B2285H U1064H U1016H
A6 - SCM : U1300H U1255H
B0 - RFA : C2100HC U1000H U1255H U1064H U1096H U1016H

 

Here ya go, Greg:
Wheel Speed Sensors

Back to the wheel speed sensors. Code C1221 - 1228 indicate that one of the wheel speed sensors is either sending a bad signal or no signal. Start by checking the connections. The wheel speed sensors are integrated into the wheel bearing/hub assembly pictured below. The wire coming out of the back is the connection for the wheel speed sensors. Verify that the connector are not broken, damaged, or corroded in any way. Pay particular attention to the female end.

The wire coming out of the wheel speed sensor connects to and 18inch jumper harness, then to the main harness. It is very common for people to have a weak female pin in one of those connections. If all of that checks out good, Swap the jumper harness from side to side. For example if the left front is bad, swap it over to the right front. and install the good one from the right front to the left side. Then clear the trouble code. If the trouble code is now on the right side, you know the wire harness is the problem. If the code is still on the left side after swapping the jumper harnesses, you know the problem is inside the wheel speed sensors.

If all the wires check out good, it's time to take a trip to Auto Zone for a new set of bearings. You can buy replacement AC Delco bearing from your dealer if you want to, or get the exact same bearing in a different box for half the price (~$150) from Auto Zone, you decide. The bearings should be replaced in axel sets, so if your left front is bad, you have to replace the right front too. While your at it, this is a good time to upgrade the lug studs and add spindle ducts.

Greg...now, that we have that out of the way, have you considered that your EBCM may be faulty? Alot of failures out there! If you want a complete trouble-shooting file with pics, P.M. me your email address...
Bill

 

Thank you bill for your email...I've already tried to troubleshoot according to the attached document (which is very well doned... ).

In the meantime I've cleared all the stored codes. I drove the car without any upcoming failure. But this morning the ABS/TC/AH failure came up again, I then checked the codes and here they are:

TCS : C1064HC
RFA : U1000H
U1064H

If somebody can give me a clue that'd help me...
Thank you
Greg

 

Let's cover some basic information on AH, TC, and ABS. In simple terms, these three systems combine data from wheel speed sensors, yaw rate sensors, steering wheel position sensors, along with brake and throttle inputs to determine what the driver wants to do and detects any lose of traction and take corrective action by pulling back on the throttle, activating brakes on individual wheels, or releasing brake pressure as needed to maintain traction.

What goes wrong

When there is a problem anywhere in the system, the computer does not know what's going on with the car or cannot respond correctly. Rather than risking the wrong response which could potentially wreck you car, the whole system is simply disabled for the remainder of the ignition cycle. At this time you will see the ABS and Traction Control warning indicators illuminated on the instrument cluster along with the following messages on the Driver Information Center (DIC):
- Service ABS
- Service Traction System
- Service Active Handling

At this point, you can safely continue to drive your car, just remember that your electronic driving aids are no longer functioning so you should adjust your driving habits accordingly.

Troubleshooting

As I said before, when there is a problem the system is deactivated for the remainder of the ignition cycle, so sometimes everything will go back to normal if you just turn off the car and restart it. If that corrects the problem, it was either a glitch in the system, a lose connection that's going to come back soon or an early sign of a future failure that is coming. Even though the system is now functional it is still beneficial to continue to trouble shoot. The history code should give you a good idea of what to check.

Electronic Brake Control Module

The EBCM sits between the engine and radiator. The EBCM is on the left with the large wire harness coming into it and the sticker on top. The Brake Pressure Modulator Valve (BPMV) in on the right with the brake lines coming out. The EBCM is a dry module, meaning that you can change it out without having to worry about bleeding the ABS system. All of the brake fluid is contained within the BPMV. The coils fit over small spools that have valves inside them. The valves are operated by an electromagnetic field supplied by the coils.

Start by doing a quick visual inspection of the wires. If there are any obvious signs of damage, you've likely found the problem. One member had a problem with the wires rubbing the serpentine belt.

Also check to make sure the wire harness has a good connection. If the connection appears solid disconnect it (see step 3 in the replacement instructions below) check the pins to ensure that they have not been bent or damaged in any way. If there is any sign of corrosion, clean it off. Once everything looks good, reseat the harness.

Next, let's move on to the grounds. The EBCM is grounded to the chassis on the left frame rail, just forward of the engine. It's the Black box right in the middle of the picture. As you can see, it's real easy for dirt and moisture to get in that area which isn't exactly good for electronic components. Even if you never drive your car in the rain, it'll still get wet when you wash it, and that could be enough

Start by unbolting the chassis ground, then take the chassis ground connector apart.
Corrosion can build up in the ground connector. go ahead and clean it up with a wire brush before putting it back together. Also clean off the chassis and bolt to make sure you've got a good clean ground.

*If you are having any other electrical issues, it's a good idea to check the grounds.
At this point, we know all of the wires are good, but for some reason enough voltage is not getting to the system. It is possible that your battery is not functioning properly. If your battery is a couple of years old, has been drained and recharged a couple of times it might be a good idea to go ahead and replace your battery. This is a long shot for EBCM issues, but I think it's worth a shot before spending several hundred dollars for a new EBCM and you're going to have to replace it eventually anyways. Old batteries can cause a variety of minor electrical issues and you likely have a bunch of history codes for minor issues if the battery is causing the problem.

Now on the EBCM itself. If the electrical contacts inside the relay are dirty or burnt, the vibration from striking the module may change the symptoms or may clear them up for a while. This is by no means a fix or a cure all, in fact it could make it worse or it may not do anything, it's just something to try. Use a small plastic hammer or something similar, lightly tap the front of the EBCM on the lower right corner of the module. The area will be on the right hand side of the lower electrical connection .

At this point, You've got to additional possibilities. Replace the EBCM or replace both the EBCM and the BPMV. The service manual calls for you to measure the resistance between each pump motor control circuit and the housing of the BPMV, if that checks our okay, you replace the EBCM if not you replace them both. Since most people do not have the equipment to do this the best we can do is to replace the EBCM. If that doesn't work, you'll have to go back and replace the BPMV.

The procedure for replacing the EBCM is very simple. The only special tool you need is a T-20 torx screw driver. I have a Craftsman tool set that has a 1/4" drive screwdriver with and adapter for many different size bit. Unfortunately, the adapter was to long to fit between the EBCM and water pump, so I purchased a set of Craftsman 5 pc. torx screwdriver set that worked fine. A flathead screwdriver may also be needed to pry apart the EBCM from the BPMV

1 - make sure the car is off.
2 - you will probably need to remove the airbridge to get to the EBCM.
3 - remove the wire harness by first removing the white plastic clip that locks it in place (I cut it off and replaced it with a zip-tie) , then lift gray handle and pull back on the wire harness . At this point, you will be able to see the second wire connection that is removed by pulling down.
4 - The service manual call for you the remove the 2 insulator nuts that hold the BPMV to the brackets and lift the EBCM/BPMV out of the bracket. I do not think this step is necessary because there is plenty of room while it is still in the bracket and you do not gain much additional clearance since the brake lines restrict the movement.
5 - Remove the 6 T-20 torx screws connecting the EBCM and BPMV - 1 on each corner and 2 on the sides .
6 - "Separate the EBCM from the BPMV by gently pulling apart until separated" - I should start laughing here, but it's not that funny. It's been my experience that anytime the instructions call for you to do something gently, nothing gentle is going to work. In this case, I had to use a flathead screw driver to brake the seal. Once it moved a little, the rest was easy. In addition to the rubber seal, each of the 12 holes you see in picture 3 have a peg in them from the BPMV. Don't go crazy, but be prepared to force them apart.
7 - At this point, all you've got to do is put it all back together. push the new EBCM onto the BPMV.
8 - Replace the 6 T-20 torx screws
9 - reconnect the wire harness
10 - put the intake back on

At this point, the AH/TC/ABS should work normally. If not, you've also got a problem with the BPMV. Although you could replace the BPMV yourself, you have to bleed the ABS system which requires Tech II. For those of you like me that don't have access to Tech II, you've got 2 options. Replace the BPMV yourself and tow the car to a shop with Tech II to have it bled, or just take it in to have the BPMV replaced. The advantage is that you've already done all of the trouble shooting so you want have to pay the mechanic to diagnose the problem for you.

 

I have checked the wires that go to the EBCM as well as the harness...no problem here, I checked the ground which is good and now I am considering in changing or having my EBCM rebuilt but something is strange here : there are no codes related to the BCM stored, the only codes that I have are for the TCS and RFA.
What do you think?
Greg

 

It gets confusing but the TCS codes are related to the EBCM. TCS is Traction Control System and EBCM is the electronic brake control module. The EBCM plays a part in traction control.

BCM is the Body Contol Module.

I am no expert but I believe all those codes that start with the letter "U" are communication problem codes. When you start your car all the different computers have a quick check on one another. If they get something unexpected, low voltage for example, a "U" code gets posted. I always thought the "U" codes only showed up under RFA but apperently not.

Maybe others may have an idea what is causing you to have so many "U" codes.

David in AZ (Currently in China)