ABS Warning Light

[bhickmott]

Hi Guys

It's been awhile since my last post (or login for that matter), but I've still got the 98 MK8. Pulled it out of the garage after sitting for 2 years and took it for a drive. Ran fine for 20 miles then the ABS warning light came on and the brakes started to pulse. Shows brake codes of C1235 and C1236 indicating no input signal from both left and right rear wheel speed sensors.

I doubt that that both sensors could fail simulateously. Checked all connectors and the wire harness run all the way up to the ABS Control Unit and all is fine. I'd hate to think that the ABS Controll unit has probably failed.

Anyone have any ideas ?

Bill

 

[bhickmott]

ABS Warning Light - Updated

Well .... this has been a learning experience and not exactly my idea of fun !!

The connectors for the wheel speed sensors are relatively easy to get at in the trunk. Although if you are large in size you may have trouble squeezing that far into the trunk.

FYI .... The wheel speed sensors must some kind of diode as they measure 26 ohms when forward biased and no continuity when the polarity is reversed. This drove me nuts for a while as sometimes I would show continuity and then when I'd check it again continuity was gone. Soooo ... pay attention to the polarity of the ohmmeter leads when you connect to the pins. I finally figured it out.

Next step was to verify continuity of the cable run all the way to the ABS module which hidden under the battery area and just below the left headlight. There is no access from above so don't waste your time removing the battery and battery box as I did !!! You must remove the front air dam that runs the width of the vehicle to gain access to left valance area behind the left headlight.

The connector to the ABS module has a latch assembly that you must continue to work upward while you continue to work the connector outward from its seated position. Kind of difficult to figure out working from the bottom looking straight up !!! Finally figured out how the latch worked and got it off from below. I have verified that I do have continuity with both rear sensors.

FYI .... color code for wiring from the sensors ot ABS module connector:
LR = Grn/Red and Grn/Blk
RR = Red and Red/Blk

FYI .... I am told that there is an intermediate connector in the cable run from the rear sensors to the ABS module connector. This apparently is located in behind the kick panel. As I have continuity all the way to the ABS module, I did not verify this.

At this point it looks like the ABS module may be faulty. Does anyone know if
there is any way to verify or test the ABS module ? I guess I may have go to my Lincoln dealer and pay a diagnostic fee to have them run their Ford Scanner ot isolate.

Also anyone know where to locate a replace module other than the "Boneyard" ? Not sure if Ford/Lincoln offer rebuilt units from their parts program? None of the aftermarket suppliers seem to list anything.

 

[andyfanshawe]

Hi.
Sorry to hear of your problems.
I'll try to help the best I can.
I'm lucky enough to have the NGS star tester, and I have just looked up the procedure for those fault codes.

The first step is to monitor the signals from those sensors via the scan tool and check that the readings are roughly the same.

Then a self test of the ABS module is required through the star tester. It looks for code B1342 which is an indication of a faulty abs module.

BUT, this is probably no help to you!! Unless you can find someone with a star tester! How close are you to the UK? I'll scan it for free!!!!

Anyway, I have come across some of these problems before. So this may be worth a try.
Corrosion builds up under the sensors over time and changes the air gap between the sensor and the toothed wheel. There could be a small chance that during the time that the car has been standing this has happened to some degree on each side. may be worth a try to remove and clean up underneath.

If that doesn't work, do you know anyone who has a dual channel scope who can compare signals from side to side?

Just thinking out loud here, but if the pedal started pulsing the abs is working okay. its picking up a wheel speed signal that it is interpreting as dropping out.
Clean underneath and around the sensors and report back will you?

Hope this at least helps a bit.
Andy.

 

[bhickmott]

ABS Warning light - Update 2

Thanks for responding to me Andy. Wish I were closer to your NGS Star Tester !!!

No luck with the cleaning of the reluctor and the sensors. I still have both sensor codes C1235 and C1236. The car only has 60K for mileage and I painted virtually every thing on the underside when I bought the car in 2000. Nothing has rusted or corroded ever since. The car is only driven in summer and sits in a partially heated garage from November till May. To be sure, I did clean some over-spray off the reluctors and brushed the face of the sensors as well as checked for corrosion under the mounting bolt area as you suggested. All was fine.

I checked with vitually every car parts supplier online today trying to find both rear wheel sensors. Nobody makes new replacements anymore. I found a local junkyard with 3 1998 Marks and had them to ship me a pair of rears sensors and the ABS Control module. I still don't believe my sensors are bad, but seeing how rare these items are I felt it was a wise investment for the future. Wish they could get the front sensors as well, but they agreed with me that they are virtually impossible to remove without destroying them (they rust in place). Plus they can sell the whole spindle for more money !

Someone posted a test routine for Gen 1 Marks on the other Mark Forum website, but the Red connector they mention on the Gen 1 doesn't look anything like what appears to be the White ABS Test connector on the Gen 2 Mark. This connector can be found right behind the left headlight assembly. Anyways the test involves grounding one of the pins in the connector and the ABS Warning light will "blink out" a failure code. Have you seen anything like this for Gen 2 Marks ?

When I receive the sensors and ABS Module I'll let you know how I make out. If they don't fix the problem I guess I just have to pull fuse # 21 and drive with NO ABS, but unfortunately that kills the speedometer as well.

Best,

Bill

 

[14.6@97MPH]

Bill - Please keep us updated with your abs problems.

I have a very similar problem with my 1998. I've had check abs/check traction control for a while now and its annoying. I've already replaced my abs module twice. The last replacement lasted about 6-months and I had no warning lights during that time.

The current ABS problems on my car started this time with a jumpy speedo, which according to the message boards in my rear sensors. The speedo isn't jumpy anymore, but I get the ABS light and warning every time I get to the self test speed.

My only advise, from what I've learned, is try and get junked parts from southern cars. The salty roads up north seem to be part of the cause for the modules and sensors to go.

Ken

 

[mark82nv]

i get abs traction control warning on my 97 my speedo doesnt work and the od doesnt work either and the message board says data logging entry error can this be the module or speed sensor?

 

[AndyT]

The issue with 98 rear speed sensors is they are a 98 specific part. They differ from the 97 sensors. They aren't made anymore by Ford either, or an aftermarket company either from what I remember.

 

[bhickmott]

ABS Warning Light - RESOLVED !!!

Glad to say that the problem seems finally resolved !!!

Looks like it was the ABS Controller module, but I have only driven a couple miles since replacing the unit. Ran into a lot of issues in making the swap so let me give a few details should someone else encounter this ABS failure problem or a "Bouncy" speedometer.

First, the ABS module failure seems to be fairly common problem on these cars. I had a good conversation with the owner of the "Boneyard" where I purchased a Module (and both rear wheel sensors) and he said he had sold a lot of these units over the years. Ford does not carry these parts anymore nor do they offer an exchange or repair program. Additionally, No one in the after market makes the wheel speed sensors anymore. These parts are getting really scarce, so I would advise all MARK owners to BUY A SPARE NOW !

A few tips on ABS module replacement ....
Make sure you have a good E5 External torx socket. (most standard sets only go down to E6 as was my case, so I had to scramble to find one) There are 4 small screws with Torx E5 heads that hold the unit in place on the ABS valve body. These were very rusty and corrosion was evident the entire length of screw shaft. Two of the screws were very difficult to remove as the threads into the valve body had corroded. To be able to get at the screws unobstructed, I removed the electric SMOG pump that is mounted in front of the ABS module. This allows you give each screw a few solid raps with a hammer to loosen their "set" and to hammer the E5 Torx socket firmly onto the screw head. Work the screw very carefully as they look like they could break easily. I didn't use any penetrating oil, but that might be something to try if you encounter strong resistance. When I installed the replacement ABS module I cleaned the valve body with a silicone spray dampened cloth and gave the Module inards a spray as well. I coated the screw shafts and the module's screw sleeves with "Never Seize" compound. Once the unit was bolted in place I coated the screw heads with a good gob of RTV silicone to hopefully prevent future rust.

Once installed, I connected the Actron Brake Analyzer and reset the the C1235 and C1236 failure codes and test drove the car down the driveway. I still had a small amount of ABS Chatter (Nothing close to the original problem) and I thought to myself "DAMN, the problem is still here !" Then I noticed a really bouncy speedometer. I activated the Actron Brake analyzer, but it showed no failure codes this time. This new problem turned out to be that the right rear wheel sensor connector was not fully seated into its recepticle in the trunk (I did try both replacement sensors that I got from the boneyard just to verify that they are good)

So this is hopefully the end of the Saga !!! If anything changes I'll let you know.

I wince to think about what to do if a front wheel sensor fails. Boneyard units can NOT be removed without breakage and aftermarket units are NOT available. Anybody have any ideas ?

Bill