Mechanics

ABS CONTROL MODULE FAILURE

2002 Ford Windstar

Electrical problem
2002 Ford Windstar 6 cyl Front Wheel Drive Automatic 84000 miles

Question: Is there a way to completely bypass the ABS Control Module so that the dash will work? Anybody got a pin-out for the connector? My thought is that if I can get the speed sensor signal to the dash and just completely disconnect the Control module, I should be able to drive the car.


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Here's my writeup to the NHTSA:

The morning of July 11, 2010, the ABS Control Module on our 2002 Windstar suffered an internal fire due to brake fluid leaked from the bad switch, resulting in a loss of proper brake function and no readings from the speedometer, tachometer, and odometer (as well as multiple warning lights). This occurred several weeks after having had the Brake Pressure Deactivation Switch recall performed (NHTSA Campaign ID 09V399000, Action Number EA08021). The local Ford dealership which had performed the initial recall work refused to repair or replace the module under the recall or as a warranty claim, stating that it was not part of the recall, nor was it apparently damaged at the time of the brake switch repair. I subsequently removed, opened and examined the control module (8/28/2010), and found blackened brake fluid present inside the module at the connector pins. I also found evidence of significant burning around the pins at the connections to the printed circuit board. This evidence included the blackened fluid, severe discoloration, and lifted traces, all of which are clearly apparent in photos of the module interior. Luckily, it appears that an internal trace burned through and interrupted the fault current prior to the failure becoming a runaway fire event. At this time the vehicle has not been repaired, and is sitting idle. I have kept the failed Control Module for examination
as necessary.
Avatar
FullThrottle64
August 29, 2010.



Hi FullThrottle64. Welcome to the forum. I don't think brake fluid is the culprit unless you actually see it running out. Modules under the hood are so well sealed, otherwise rain water would get in. The burning looks like a typical failure which is common on a lot of computer modules on a lot of brands of cars.

The most common failure is a shorted " reverse polarity protection diode". It's job is to turn on and conduct a real heavy current and cause a fuse to blow if the battery is connected backwards. Blowing the fuse saves the module. Those diodes are used in computer modules, car radios, and lots of other devices that would be damaged by reverse polarity. Unfortunately, those diodes cause as much trouble as they prevent. Even if brake fluid did get onto the circuit board, it isn't electrically conductive. I've seen the same failure on a Mitsubishi Eclipse Engine Computer, a Chevy Blazer ABS computer, and a few others that I don't recall the specifics. Adding to the misery is the fact that these computers run a number of high-current solenoids in the hydraulic controller. That high current is hard on the pins in the connector and can lead to degraded solder connections where the pins attach to the circuit board.

I've had limited success in cleaning off the carbon and soldering in wires to replace the burned traces. Usually there are other things wrong internally.

As a side note, check all the fuses under the hood and inside for your instrument cluster problem. The signals may be shared by various modules but I believe you don't HAVE to have the ABS module to have gauges. I could be wrong on that, but on most vehicles, the ABS is an option. If it isn't on the vehicle, the rest of the components are the same.

Caradiodoc

Caradiodoc
Aug 29, 2010.
When I disconnected the plug from the module, there was about 2 oz of brake fluid present - it dripped all over me.

1) This module isn't located under the hood.
2) The most common failure point for an otherwise liquid-tight electronic assembly is the attached wiring. Making the housing liquid-tight is one thing, but making the attached wiring liquid-tight is another issue altogether. There is a capillary effect that pulls the fluid down inside the wire itself, along the copper strands. This is well-known in the electronics industry, and has been previously documented in the case of this particular controller. Are you aware of the Brake Pressure Switch recall that I mentioned and the ABS Module fires that have been associated with it? What has been happening is that the brake pressure sensor at the master cylinder has been failing and allowing brake fluid to go down through the wiring harness to the ABS Control Module (located under the drivers' seat, right below the fuel line).

There is still brake fluid present at the burned area. I am an electrical engineer who has designed a LOT of electronic products - this is not a typical dry over-current failure.

No, but it is flammable, and when it gets dirty it DOES become conductive (that's why power transformers need to have their oil checked every few years).

Exactly. Combine a marginal solder joint with high fault current levels and some flammable fluid, and you have the sort of burning failure I've gotten.

I really don't care if the ABS itself works, so I feel fairly confident that if I could get a complete wiring diagram, I could jumper the speed sensor signal, and just pull the fuses that power the ABS valves. This is why I asked if anyone has a pinout they could share. Do you?

No other fuses are blown. This particular failure mode is well-known on this model; when the ABS module goes out, the speed sensor signal doesn't get to the instrument cluster, which causes the speedo and odomoter to stop functioning (makes sense if you think about it). ABS was a standard feature on this model, and the main speed sensor signal goes through the ABS module (lousy design). Unfortunately, none of the third-party manuals I've been able to source give the wiring detail for this module, so while I could probably trace out the sensor input signal fairly easily, I've no way of knowing which of the half-dozen or so lines between the ABS module and the instrument cluster actually carries the speed sensor signal.

Make sense?

Tiny
FullThrottle64
Aug 29, 2010.
Thanks for adding another dimension to my beedy little mind. I have another story about the capillary effect of which you speak, but I wasn't aware it was that common on another model or even about the recall. Seems someone had a wet floor on a fwd GM product about ten years ago. It was blamed on a leaking heater core. The problem continued after it was replaced. After numerous repair attempts, the conscientious mechanic was worried about the liquid damaging the engine computer which lives behind the right kick panel by the door so he covered it with a plastic bag. No more wet floor for a couple of months until one day when the car stopped running. Imagine their surprise when they headed for that computer and found the bag full of coolant! Upon further investigation, they found coolant in the connector of the coolant temperature sensor. So I definitely understand what you're describing. Apparently there was no other connector between the computer and sensor to stop the flow of coolant. I just never dreamed I'd ever hear of that happening again. Thank you.

I can't get my access to AllData to work, but as luck would have it, I have a bunch of Ford dvds. I think I found the diagrams you want. Even though electrical is one of my specialties, Fords and stability control systems are not. I'm familiar with the Chrysler system where speed sensor data is transferred between modules on the data buss and doesn't have to go through one module to get to another, but that may have changed for them too.

I've never worked with a yaw sensor, steering wheel position sensor, or power booster sensor so I can't help you there. I've been to schools where we talked about them but that isn't the same as actually working on them. From what I can tell from the diagrams, it appears, as you said, ABS is standard, but stability control might be optional.

I don't think I can copy and paste the diagrams here so I'm going to e-mail them directly to you. Besides, a lot of stuff I see pasted is way too small to read. I don't see any reference to the speed sensor signal so it must come in on a data buss. If that's the case, you should be able to just unplug the module without affecting anything else. Most ABS systems don't even use a vehicle speed signal. They work on the four wheel speed sensors which are not the same as the one used for the engine, transmission, and instrument cluster. That said, the system diagram, part three does show the instrument cluster, engine computer, and ABS computer all tied together with two wires that appear to be a data buss. It goes to the diagnostic connector too so you know all vehicle information related to computers will be there. I know there are some cars that use an ABS wheel speed sensor for the speedometer but I found a diagram in the transmission section that shows an input shaft, (crankshaft) speed sensor and an output shaft, (half shaft) speed sensor. That's what Chrysler uses too so the ABS should be a whole separate system. If your ABS module is shorting out the data buss, my understanding is the engine won't even start and run due to loss of sensor information, but it is possible that the ABS computer interprets the speed information before sending a different signal to the instrument cluster. I can only guess they would do that to force you get the vehicle repaired for an inoperative speedometer / odometer. There are a lot of people who would just keep driving without knowing what the ABS warning light was for if everything else worked normally. Forcing them to get the speedometer fixed would result in the ABS working again which would eliminate a potential liability issue.

Caradiodoc

Caradiodoc
Aug 30, 2010.
Great info - thanks! Now to see if I can get this thing sorted out.

Tiny
FullThrottle64
Aug 30, 2010.