Hello,

Background:
1990 F150 4x4, 5.0, AOD

What's going on:
Yesterday while going around a car that was stopped in the middle of the road, I went up on a curb and the truck came down hard as I slammed on the brakes becuase the guy desided to start driving again. Don't think it has anything to do with it (unless someone else does). Anyway, shortly after that (not sure how long, wasn't paying attention) I loo down and see both the ABS and BRAKE lights on. When I shut it off and restart it, they pass the systems check but eventually come on again, sometimes within a minute, sometimes it takes a good 5-10 minutes.

What I did:
I check brake fluid, and add a little bit since it's low, not very much. No change. I looked into the Haynes manual and started digging. I first checked the parking brake operation of the light, and it's fine. Both lights come on with ignition and go out like they should. I found the diagnostic connector under the dahs and ran the codes. It spits out a code 4 -- which translates into check a whole bunch of stuff and the book can't help you with any of it. So, I look for wires disconencted and anything funny and find nothing. At this point, I come on here and do a search for problems. After this I decide to check some of the simpler things (my motto). I check the grounds over by the battery and they don't look like new, but they look ok -- not very much corrosion. I disconenct the battery to reset the computers (and knock some corrosion off the terminals). I reconnect and go for a drive. Seems to be staying off until around 10 minutes and then they come on. I pull the sensor out of the rear end and it looks ok to me (what do I know? -- how do you tell?) so I clean it off good, along with the connectors, put dielectrical grease on them and stick it back in. Again, until 10 minutes it seems fine...then back to square one.

Now it's raining and I'm not taking my Mustang out of the garage to work on this, so here I am looking for help. I COULD try and test wires and such but I'm looking for some other opinions, I'm sure it's going to be a common problem.

So -- lay it on me, whatever you're thinking.

Thanks!

 

One more thing ... I looked at the parking brake cables and they looked a little loose, but still ok. I pushed them back as far as I could to make sure they were released and it also didn';t make any difference.

 

You may want to unhook the battery for a while and see if the computer resets itself. You may have just jarred something to cause the code. If that doesn't work, you should probably see if it's showing any codes.

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http://easyad.net/images/94vanavitar.jpg http://www.easyad.net/images/mustang1.gif

'94 E-150 Conversion Van 4.9 / C-6 -- '89 Mustang LX 5.0

 

>You may want to unhook the battery for a while and see if
>the computer resets itself. You may have just jarred
>something to cause the code. If that doesn't work, you
>should probably see if it's showing any codes.
>

I already disconnected the computr long enough to reset everything. I pulled codes from the ABS computer, should I bother pulling them from the ECU as well?

 

I got a code 4 from my 88 F150, did all the ohms and voltage checks according to Mitchell manuals, still pointed to a bad ABS module. Code 4 is for the valve but the module can still be bad.
Phil

 

Ok -- was fine for quite a while, then started happening again.

Last time I cleaned off the rearend sensor, but it seemed fine (not sure how you know if it's bad).

I tried pulling codes again, and I'm not even sure I'm reading right. I get 4 short flashes repeating - but the book indicated the lastflash should be long -- which is wasn't -- just four shorts repeating.

Had trouble finding the module to check resistance, as I'm beginning to suspect some wiring somewhere. Both lights come on at no perticular pattern -- could be one minute of driving or 45 minutes.

I'm about ready to drive this thing off a cliff -- help me out here!

 

Help!

 

Take it out,nail the brakes hard see if the the brake bias seems goofy. The solenoid operated brake bias valve is prone to sticking at one end of the travel after they get old and dirty. I had to replace one on a '91( don't remember what it cost). Good Luck.

 

Everything seems fine with the brakes to me. It seems to stop as good as I'd expect from a truck, doesn't pull or do anything funny. This is why I'm baffled -- everythign seems fine, but still I get the light ... sometimes.

Today, I did plenty of driving and no light. I also did a little coolant work so the engine tends to run a little cooler, and is cooler under the hood. Possible heat problem?