It is the craziest thing in the world.... When I go over 45 mph and then try to stop and step on the breaks my car tries to accelerate and run away on me!

Has anyone ever seen this or dealt with this problem? No one i asked has any kind of a clue.

Please help.

 

Malfunctioning cruise control ??
First time I have ever heard of this here

 

I am super concerned I was with my wife on the highway when it went crazy, 75 mph with no breaks because it was running away on me. I had to throw it in neutral to be able to stop.

 

If I replace the cruise control switch assemvly do you think it will fix it?

 

I wouldn't start throwing parts at the problem
That can get costly
Lets see if anyone else here can add any info regarding this problem
How long have you had the car ??

 

I bought it used and have had it over a year, my cruise control stopped working a handful of months ago and then soon after my car started acting possessed. I had a guy try to charge me 750/to replace the cruise control assembly and the brake pressure switch.

 

Well, that kinda sums it up, doesn't it? So, I THINK we can somewhat safely assume that the issue here is a defect in the Cruise Control. Only problem is, there is no cruise control. What I mean is, the "cruise control" is an application that runs in the PTCM. So just replace the PTCM and all is ok, right?

Well, even THAT expensive option may not fix it - because we don't know if the PTCM is doing this because of bad data coming from a speed sensor somewhere, or maybe the cruise switch assembly (referred to in the manual as the "speed control switch".

The brake pressure switch tells the cruise to disengage - so that would fix it if the cruise is not dis- engaging after being set. As to the switch assembly, well, read on.

The ACEL/SET line coming from the "Speed Control Switch" (I assume that is what is meant by "Cruise Control Assembly -since there isn't such an assembly in the car) COULD be the issue. IF that line is "high" at the input to the PTCM, then the PTCM is doing what it was designed to do, it is accelerating in command from a defective switch.

By monitoring that input, you could 'see' the line go high and when it does, the car would take off on you. But it would be hard to watch that line with a meter while driving. But you could CUT or DISCONNECT that line at the PTCM and see if the car acts up. If that ends the problem, then I would change the switch assembly.

If you are going to troubleshoot this yourself, you really need the service manual. I'd suggest you download it from this forum and start reading. Page 8P-8 of the SRT manual is what I am looking at (well, the whole chapter, but the diagram is on that page).

 

One other thing...

My car did something odd twice last year. After shutting the car off and letting it set for 5-10 minutes, I start it back up and head down hill. I realize I am speeding up - and I press the clutch and the engine races to the red end of the tach! It hovers around 3500 to 4500. Out of "what do I do now?" I turn the key off and coast to a stop.

Restarting the car and driving off, I dont' experience it again. Until, about a month or two later, when I start the car up warm and head down hill - and it does it AGAIN.
NO ONE on this forum has reported this happening but me. The car has not done it since. Sound familiar?

I replaced the battery (because it was four years old and I always buy the cheapest battery and change it every four years) and like I said, it has not done it since.



Ok, one MORE thing....

Which brings us to the next thought: Our cars have all sorts of issues with a weak battery. How old is yours? As I said before, I buy the cheapest battery that meets the CCA requirements of the car and change it often. By trying to stretch a battery for years and years, you same some money, UNTIL you need a tow someday because it failed.

OR....

Until some weird electrical issue pops up and you throw parts and money at the car, guessing at what is wrong, when the simplest (and pretty cheap and easy) item, the battery, gets ignored.

SO, um, how old is the battery? (And if you respond with, "Oh, I had it tested by some smelly guy in a dirty shirt and he said it was fine", I will NEVER respond to your posts again. I did NOT ask you if you had it "tested", I asked how old it is.)



Remember, the battery has one big job: Provide several hundred amps of current to turn the engine over to get it started, while maintaining at least 11 or so volts. When you get your battery "tested", they put a fractional ohm load on it and see how much current it produces and if it can maintain voltage.

Most people think the battery's job is over when the engine starts because "the alternator takes the electrical load from there, and recharges the battery". Which is true, but that is NOT the end of the battery's job. The alternator puts out rectified three phase AC, not DC. That is to say, it puts out "bumps" of voltage/current that look like NOISE to all the electrical modules in the car. The battery's second job is to smooth out the bumps, that is, it is a filter. If the battery is no longer filtering well, it COULD be that the PTCM is falling into confusion due to the "dirty power" it is being fed with.

When you get your battery tested, to test the filtering capability takes an oscilloscope and enough knowledge to use it. The result is, the battery is not tested for it's filtering capacity. So don't waste your time "getting the battery tested". (Of COURSE, if the battery DOES fail the capacity test, replace it; I am just saying that a passed capacity test is not a complete test and that you should NOT start throwing parts at the car if you won't start with the battery.)

 

Why say battery and cruise control? I would tend to think of the throttle pedal and throttle body electronics causing the problems.
If you are using a Sprint Booster I would disconnect it for now.

 

A lot of good replies here. I absolutely MUST point out that the brake switch input is a safety that overrides all others for the design of the cruise control system. If a mechanic has diagnosed something wrong with the brake switch, I would go ahead and replace that AFTER I eliminated the battery issue. Going through the manual to troubleshoot the control wiring (at the BCM leading to the switch assembly at the column) would be hard enough for someone but if this wiring is an 'intermittent' then good luck in having it fail while your testing these various wires 'continuity'. The cruise control wiring bundle is wired/designed to operate the system but the brake cutoff circuit is a primary safety system above the protocol of the operation of the system. On a second note, I have seen more and more suspicious activity around high EMI locations. Our cars are being deluged with systems easily interfere with by high EMR in locations that transmit these signals. If a shielding discrepancy is causing this, there will be no amount of parts thrown at the car that will eliminate it. IMHO.

 

It looks like there would be a DRBIII code P0575 if the switch reports an incorrect voltage so it should be easy to know if the switch were bad by a DRBIII owner.

The speed control switch gets power from 5 amp fuse #10 in the under hood accy. fuseblock, was that checked?

 

Do you have aftermarket floor mats? I had a Toyota that the floor mat would work its way up and trap the gas pedal when floored... I quickly discarded the floor mats.

If you are already having issues with your cruise control more than likely an electrical problem, so please follow the great advice already posted. Just wanted to mention the floor mat just in case.

Ryan

 

This member, who joined one week ago, has not posted since posting four times that day. I think he has solved the problem and we will not hear from him again until he has another problem.
I say we forget about him.

 

Agreed, Dave