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how to hard reset sebring TCM/ECM/ECU/PCM

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 PostPosted: Sun Dec 09, 2012 10:42 am   
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Seems these acronyms get used quite often when talking about the "computer", but I have a very rough idle and I need to reset the "computer". I read that I could disconnect the negative terminal wire for 5-60 minutes and it will hard reset and have done this, but is there an actual method for doing this without disconnecting the battery?

I read somewhere in a 4 yro old post about holding down the parking brake and doing some rain dancing and such, but it made no sense at all. -a guy wrote something about holding the parking brake to the floor, even though the parking brake isn't on the floor. what he was getting at, I couldn't make out.

also for further reference, are the TCM/ECM/ECU/PCM modules in the sebring hard coded to a VIN?
Would there be any problems if I swapped out the 2 modules for junkyard versions of the same make and model?

TIA


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 PostPosted: Sun Dec 09, 2012 10:53 am   
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well I'm guessing that you would have to connect it up to a DRB scanner (which is usually restricted to a dealer of repair facility due to the cost of this machine) is the check engine light on? If it is, even a trip to a place like Autozone can check the codes that come up for you (free of charge, but most won't reset it, unless you buy parts to "fix" it from them) never heard of that parking brake thing...you might ba talking about what they call the key dance...I don't remember how many times you have to do it but it involves turning the key to the on position ,but not starting it, and off again 3 or 4 times in 10 seconds...then the display will flash...you count the flashes to get the code (I think it's in the manual, with some) and not all years do it...
I'm sure someone will correct me and get you a better description, soon!


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 PostPosted: Sun Dec 09, 2012 11:01 am   
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You've got a 99 JXi. There are three primary modules used on this year that talk to each other.

The PCM (Powertrain Control Module - Electronic engine management), the TCM (Transmission Control Module - Electronic transmission management) and the BCM (Body Control Module - Electronic interface for operator inputs and displays). These communicate over an internal network called CCD (Chrysler Communications Databus IIRC).

Depending on the specific model and options they can "imprint" one another. Particularly any options that are security related. It's not something to change out on a whim since you might get ahold of a module that has an activated option that your car doesn't have, install it causing the other related modules to pick up on that option and then report it faulted because it isn't there. The worst potential is the Sentry Key module which will completely disable the car.

Having thrown out that info, resetting any DTC's (Diagnostic trouble codes) is all that the removal of power does. If you don't fix the cause of the code then it will come right back.

Now for the worst part of the news, be very careful on the 99 model. There is NO provision on this year, 98 or 2000 for readout of ANY DTC to the owner. You MUST use a code reader at a minimum. The "Key Dance" that is often talked about in most Chrysler forums does NOT work on these years.

So, what has you thinking about replacing something that we've rarely seen go bad? Have you been able to retrieve any DTC codes from a reader?

BTW, I own a 99 with 240,000 miles on it. :evilsmile:


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 PostPosted: Sun Dec 09, 2012 11:15 am   
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:yeahthat: :yeahthat: :yeahthat:

Whoa there MMDSebring.....Don't do brain surgery because you aren't clicking on all cylinders when you first wake up......

Again, check for codes...did you have a check engine light? If not, there are many other reasons you may have a rough idle without throwing a CEL code.

Current mileage?

Last tune up?

Vacuum leaks? etc.......how rough is the idle? Does it stall if just left to idle? Besides a rough idle, does it run perfectly well under normal & heavy accelleration?

I personally would suspect everything else before the computer systems.

Bob


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 PostPosted: Sun Dec 09, 2012 11:29 am   
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:yeahthat: :yeahthat: :yeahthat: Run (er.....drive), don't walk to the nearest Advance Auto or Auto Zone and have them hook up their code readers if you don't have one. That's the starting point. From there, you should be able to find all the help you need right here unless it's a simple fix (based upon codes) they can help you with at the store.


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 PostPosted: Sun Dec 09, 2012 12:07 pm   
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:yeahthat: What everyone said. That being said when I worked for Lincoln Mercury to reset some of the computers at that time many years ago. :nono: :nono: We had to turn the key to on without starting the vehicle and hold the gas pedal to the floor. This would reset the air ride computer and some of the other stuff. This might be what your friend is talking about. I don't see it hurting anything on the sebrings so give it a try. Let us know what happens. Key to on no start gas pedal to floor hold it for about 30 seconds release pedal and start the car.


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 PostPosted: Mon Dec 10, 2012 9:05 am   
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Terry W.. That is incredible.....now, what engineer designed that fix??? :confused:

Now, I have to admit, I am seriously thinking about trying it on the F150 just to see what happens.. :rofl: :rofl: :rofl:

I don't have air ride but I have "other stuff" I guess....

Bob


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 PostPosted: Mon Dec 10, 2012 10:40 am   
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Give it a try Bob. You never know what it might fix :thumbsup:

My radio control stuff works a lot like that. You reset a lot of things with the throttle control and this is all state of the art equipment. :throwpc: if that doesn't work you can always throw a hammer at it. :rofl: :rofl:


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 PostPosted: Fri Dec 14, 2012 2:01 pm   
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Oh man fellas, this is great!

Alright, reasoning behind me looking into the computer is simple.

symptoms listed in order of occurrence in the last 6+ months:

an intermittent kind of studder in the idle once the car is warmed up.
rough idle.
hesitation.
much rougher idle.
lower fuel starved sounding rougher idle.

-----------

Now, after some research I came to the conclusion the intermittent studdering in the idle, may have been from oil getting past the sparkplug seals.
Then fudging up the CPS, which this awesome video shows how to remove http://www.youtube.com/watch?v=oT8WOiYfZWA
but haven't been able to afford it, even from a local junkyard. However, from what I can tell all this requires some ground work,

sparkplug seals, 25 bucks
gaskets, at least 45 but possibly more
CPS $? probably 30 bucks at the junkyard.
possibly new computer, probably 30 at the junkyard, if they are not locked to VIN.

--------------

then needing to do all this in one session, and I can't afford to pay for it or throw money at possibilities.

Background:
This being my mom's car, hence the name, I can't go and buy her the parts since I have my own car to deal with.
I can work on her car anytime, and I don't have any problem when I know what needs to be done,
but I don't have access to it while she is at work unless she takes my car which isn't registered yet (dangerous) here in florida.
As far as money goes I don't have any money to throw at all her stuff that seems to go wrong all the time,
and I would never ask her to pay me for fixing her stuff anyway.

I'm left with less than bare minimum in every situation unless I pay for it,
which gets very costly very quick, and ultimately continues to mess up my finances.
Worst part of this is that even though she works she spends way beyond her means
and can't manage her money at all, and I can't do a thing about it.
so every few days sometimes a week before her payday, she let's her bank account get down into single digits, and comes begging me for money.
I'm just lucky, no credit card companies will give her anymore cards to burn up, but I made a huge mistake mentioning AMScott to her.

Before I got to FL, she was driving the car without a working cooling fan for approx. 6 months.
she was just able to get to work before the car would overheat.
As far as I can tell, the heads and block have not warped.

-----

So that's my situation. I have to calculate this to the point I know exactly what to fix, before it's ran dead.

This gives me an idea though to find out how useful the CPS actually is, and if I could run the car for a while
without it connected since it seems to be part of the main issue.


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 PostPosted: Sat Dec 15, 2012 11:32 am   
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2.5L engines have two primary sensors that control fuel timing and spark timing. Both unfortunately are often referred to as CPS since one is the Crankshaft Position Sensor while the other is the Camshaft Position Sensor.

Here's what I would do.

Very thorough inspection of wiring and connections along the backside of the engine and transmission especially if anyone else has attempted repairs or diagnosis.

Check the age of the battery. If it is over 3 years old, consider a replacement. These cars are VERY finicky when available power fluctuates. Nearly every item on the car is monitored or controlled electronically and it's not a very big difference between power production and consumption when all is healthy.

Take the car to a place that will read the ODBII DTC (diagnostic trouble codes in a PXXXX format) for free. Then bring them back here. Chrysler, in their infinite wisdom, designed the car's "operating system" to NOT be able to report any codes through the dash by not programming in the "Key Dance" that is still used today. This mistake (my word) affect 98, 99 and 2000. BTW, most PCMs, TCMs, and BCMs will set a code indicating they have gone bad.

Pull the front timing belt inspection cover, at the passenger's side end of the front head (3 10mm bolts and a plastic cover). Verify the belt is in good shape and if not begin planning replacement of it and a few other items. Recommended replacement is every 100,000 miles.

The Crankshaft Position Sensor is next. If and when you replace it, use Chrysler if possible. Don't waste your time with j/y on this one especially if they are $30 a pop. Aftermarket have a higher "out-of-box" failure rate than the manufacturers and this is just too simple and inexpensive, relatively,to screw around. A new one with some shopping can be had around $50 to $60. It's mounted on the back, upper side of the bellhousing with the wiring harness running down the back side of the transmission to the firewall. It will be accessible from either above or through the driver's side wheel well. Please look into the recent posts by a couple of members regarding serious difficulties in removing the old sensor. This sensor sends the information about the crankshaft to the PCM so that spark timing can be initially set. It is a Hall Effect sensor (magnetic fields) and weakens with both time and heat. Both of which are present in serious quantities on a 99. ;) More "running" issues with the 2.5L engine have been cleared up with this sensor. Disconnecting this sensor will more than likely cause a DTC and put the car into "Limp Mode" if it runs at all. Most of the time, the PCM will shut down the fuel pump for lack of signal.

The Camshaft Position Sensor is part of the distributor. Historically, if you want to replace the Camshaft Position Sensor, you'll have to buy the complete distributor-coil-sensor unit. Cardone Select has proven to be reasonably reliable rebuild of this unit and often found around $250. Supposedly there has been a replacement sensor only introduced recently but I don't remember anyone reporting here of a successful install of the sensor only repair. A new assembly has been priced at $1,400 recently. This unit can be found in the j/y and used with reasonable success but the Camshaft Position Sensor is not as often the problem as the Crankshaft Position Sensor. If you use a j/y distributor, inspect it very closely for swelling or a "burnt" smell. One of the ignition issue sources is an overheating coil. When it starts overheating, the body of it is often swollen from the internal heat. The Camshaft Position Sensor allows the PCM to refine the spark timing when added to the Crankshaft Position Sensor. The PCM also uses this signal to determine the fuel injection timing and duration. It too is a Hall Effect Sensor and reads a shaft running from the end of the back camshaft through the sensor and driving the rotor in the distributor. A lack of a signal from this sensor will also cause the PCM to shut off the fuel.

There is also a MAP sensor on this engine that will cause similar symptoms but this has been reported much less frequently as the "fix" that worked than the Crankshaft and Camshaft Sensors. My memory is this is around $50 aftermarket.

As I mentioned earlier, the key to swapping modules is to find a j/y module with similar options. If you get the wrong one it often will disable the car because of security options that it can't find but expects. And there hasn't been many folks that have had to replace their PCM on the 1st gens.

I hope this helps.


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 PostPosted: Sat Dec 15, 2012 12:02 pm   
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What you are describing with the rough idle, hesitation, etc., could be a vacuum leak
causing a lean air/fuel condition. When the motor is cold it will run a bit rich, (more gas)
to compensate for the cold motor. It does not seem to be caused by the EGR or O2
sensors as they would light the 'check engine' lamp and is why I am suspecting a vacuum
leak. Check out the pcv hose as it may develop cracks that are not apparent unless the
hose is handled.

Hope this helps,

Gerry G.


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