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Discussion Starter #1
1996 2500 4X4 5speed RWAL. My ABS and Brake lights have been coming on. I know these trucks have issues with the stoplight switch & speed sensor. The only thing is that the lights are coming on and off completely at random. Most recently they hadn't come on for over 2 weeks. Then all of a sudden they popped up this morning and have been coming on/going out all day. They'll come on fairly consistently for a couple of days, then just stop coming on all together for a week or more. Over the course of 3 months the lights have come on both hot/cold, when braking/when not braking, forward/reverse, bumpy/smooth roads, neutral/in gear, idling/70mph. Sometimes the lights are solid, sometimes they flicker, sometimes they're full on, sometimes they're dim. You name it, it's done it. Sometimes the lights go out on their own, sometimes I have to cycle the key. The only thing that has been consistent about it is the fact that it hasn't been consistent at all, lol!! Vacuum seems to be good, fluid level is okay, stopping power is decent considering I'm spinning 35s. The pedal feels alright and is consistent, brakelights work, speedo works, replaced bulbs, I tried jiggling the wires at the ABS brain and at the proportioning valve and neither make the lights flash. Brake booster? Master cylinder? Proportioning valve? Calipers/wheel cylinders? Speed sensor? Stoplight switch? Vacuum switch? I think my next plan is to flush the DOT 3 but would love to compare ideas with you. Thanks in advance guys.
 

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Sounds like a typical bad connection but it makes me wonder if the connection was fixed if the lights would then be on all the time.
Play around with the ABS relay in the underhood box, maybe swap it with another.
 

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I don't think they'd stay lit because when the light is off the ABS works. Which also means the relay should be good (should being the key word). Something somewhere is either loose or falling in and out of the parameters. I'd like to avoid busting out the ohmmeter and ripping apart the wiring harness. If it were something in the ABS system then would the Brake light come on with it? I've heard that the Brake light always trips the ABS light but the ABS light doesn't necessarily trip the Brake light??
 

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I've heard that the Brake light always trips the ABS light but the ABS light doesn't necessarily trip the Brake light??
Not always.
If you have low fluid or low vacuum just the brake light will come on.
 
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bumb from me

i had the same problem for a couple months, then they just stayed on all the time. Still havent done anything about it.
 

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Discussion Starter #6
The fluid level is fine. I've been kicking around the idea of a vacuum issue for a while now but it just seems weird to me... Either you have a vacuum leak or you don't... I did find a while ago that my cruise control dashpot was rusted out (genius design putting it under the battery tray) so I capped off the vacuum line to it and then it didn't come on for 18 days... until just this morning. Just for s and giggles I unplugged the ABS connector, the lights came on and stayed on so I know they are capable of doing so... So whatever my problem is, it isn't enough to set a "hard code"
 

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Just my 2 cents,
On my 94 the same thing was happening with my lights randomly going on and off, I finally made it home with both lights on and was able to get the code. Ended up being my brake light switch which I thought was fine due to the fact my brake lights worked fine. I learned the switch has 3 sets of contacts, one for the brake lights, one for the abs, and another that the pcm looks at. Any slight pitting on the contacts may cause problems. I changed it and solved my abs lights and also my cruise control problem. About 24 bucks..:party018:
Good-Luck!!
 

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$24!!!!!!
They must jack up the prices in NJ :)
Paid $12 at Napa a few months ago.
 
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sweet, im gonna go buy me a brake light switch today. Hopefully get them lights off my dash, otherwise ill have to use some good ol black electrical tape to cover up the lights. oh wait, this isnt my Ranger, haha
 

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Bill,
Everything here in N.J. is more money:banghead:
Does not surprise me that my local auto parts store is a ripoff. I guess I should find a Nappa near me.
 

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Discussion Starter #11
I picked up the brake light switch...$9. I love working at a parts store :) so far no lights but thats not really saying much...
 

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Johny,
9 bucks!!!!!!!!!! you stink!!!!!!!!!! I need to get a part time job at an auto parts place just for the discount!!!!!!!!
Lets keep our fingers crossed, hope that's all it is.:chicken:
 

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Discussion Starter #14
yeah, the discount definitely helps. BUT the light came back on this morning... after some research on Mitchell Ondemand I found out the brakelight switch is staying on cuz it isn't adjusted right so I bent the bracket and we'll see.
 

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Been having the same issue myself, lights on/off at inconsistent times and speedo works/doesn't work at times too. Changed rear speed sensor and nothing, I'm thinking my problem is broken wiring from rocks (somewhere near the rear end) but too lazy yet to check lol.
Subscribed though, would like to know if the switch fixes it for ya...
 

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Discussion Starter #16
Still having issues... tons of conflicting symptoms. Does anybody know where the "brake warning switch" is located? The wiring diagram says it's on the left frame rail... I am not talking about the ones on the brake & e-brake pedal. It's a circuit breaker that turns the ABS light on
 

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Discussion Starter #17
Been having the same issue myself, lights on/off at inconsistent times and speedo works/doesn't work at times too. Changed rear speed sensor and nothin
The speed sensor that controls the speedo is in the transmission... when the sensor in transmission and the one in the diff get conflicting inputs, it trips the ABS light. I'd replace the sensor in the tranny if your speedo is acting up.
 

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c my abs and brake light r on but i truckd about a 350lb hog one night and ran over it... yea it wasnt good but i think mine may have come unplugged but my ? is where is the abs sensors? front or back or both and it has to be on the passenger side of my truck.. i have yet to have probs with my speedo or lights tho..
 

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i hahad. have the same problem, however when mine does it the blower motor for ac wont come on. all i do is shut off, turn on and vwaaaalaaaaa, problem solved. i think a starter costs a littole more than that switch though huh?
 
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