I put a new pcm in the car it turns on but run.

Tiny
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  • 2002 DODGE DURANGO

I put a new pcm in the car it turns on but run roughly and the dash board stays lit up and no gauges work, if I were to put the old pcm back in woul it have to be fix for what the odometer says

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Friday, November 9th, 2012 AT 9:45 PM

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Tiny
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The vehicle's mileage is stored in the instrument cluster. You can read the mileage in the Engine Computer too with a scanner but that is not for the odometer.

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Friday, November 9th, 2012 AT 10:46 PM
Tiny
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Ok so another qustion we put the new Pcm in but the truck runs like crap and none of the gauges work and all the light sensors light up and don't turn off. But they were working just fine before we put the new Pcm in.

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Saturday, November 10th, 2012 AT 12:27 AM
Tiny
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Don't have an answer for that. Chrysler has very little trouble with their Engine Computers. What was the original problem or reason for replacing it?

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Saturday, November 10th, 2012 AT 5:26 AM
Tiny
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The reason for changing was it started to turn off and it would crank but no start say no bus and no gauges worked so we did all the tests and to no prevail so only next option was to. Changethe pcm.

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Saturday, November 10th, 2012 AT 7:03 PM
Tiny
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The "Data Buss" originates in the Body Computer. It's a pair of wires that connect all of the many computers to each other so they can share information. Roughly 6.0 volts is on both wires. That's what comes from the Body Computer. Anything that shorts one of those wires to ground or that shorts the two wires together will cause the buss to not work and none of the computers, including the Engine Computer, will get the turn-on signal to start working.

We were taught that any computer on the vehicle could develop an internal short that could kill the data buss and result in a no-start condition, but in my experience there's too much circuitry in them isolating a potential short from the buss. I've never run into a different computer itself causing a no-start. The problem is most commonly caused by the Body Computer or its connector terminals not making a good contact.

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Sunday, November 11th, 2012 AT 3:57 AM
Tiny
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So what do you recommend the gun the truck to start in runs but it's running rough then again just work all the sensor lights in the dashboard but still it the alternator is still kinda whinny and doesn't shut off like before although the way it runs it sounds like its getting ready to die out kinda like when you run out of gas.I'm running out of ideas.

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Sunday, November 11th, 2012 AT 8:14 AM
Tiny
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Wow, that's quite a sentence. Depending on how I read it, it got the rough running and a hint of low idle speed. The low idle is due to disconnecting the Engine Computer. (Disconnecting the battery will cause the same low idle speed).

The Engine Computer lost its memory and has to relearn "minimum throttle" before it will know when it must be in control of idle speed. It also might not give you the normal "idle flare-up" to 1500 rpm when you start the engine. To meet the conditions for the relearn to take place, drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the brake or gas pedals.

For the rough running I'd start with normal tune-up stuff like spark plugs and wires. If the Check Engine light is on, there will be a diagnostic fault code stored in the Engine Computer. Those codes will get you to the circuit or system that needs further diagnosis. There are some codes that indicate which cylinder is misfiring.

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Sunday, November 11th, 2012 AT 8:58 AM
Tiny
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Sorry I did not proof read the last message. But there still leaves the problem with dashboard not working none of the gauges are working at all. They were working on and off when the old pcm was in. The only time they woul't work was when the truck didn't want to start and now the truck starts up no but none of the gauges are responding at all. Hopefully this can be fixed

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Sunday, November 11th, 2012 AT 10:54 AM
Tiny
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That goes back to the Body Computer. He gets the information from all the other computers, then sends it back out on the data buss. The instrument cluster receives that information on the buss and picks out what it needs to run the gauges.

If you see "no buss" in the odometer display, the cluster isn't getting information from the Body Computer. To not overlook something simple, measure the battery voltage. If you find around 11 volts, it has a shorted cell. Low system voltage can prevent the Body Computer from working or will make it do strange things.

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Sunday, November 11th, 2012 AT 11:14 AM
Tiny
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Thanks a bunch we are going to check all and if I still have an issue I will be sure to come back with some more questions. Thanx

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Sunday, November 11th, 2012 AT 12:37 PM
Tiny
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No good news. Nothing in the dash board works all the lights are lit up. We have the new pcm in and the trucks overdrive doesn't work when we are on the freeway. And don't know how fast I'm going because all the gauges font work. What to do now?

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Tuesday, November 13th, 2012 AT 6:33 AM
Tiny
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It sounds like it's time to get the dealer involved unless you can find a scanner that will display live data so you can see what's going on. The Chrysler DRB3 will access all of the computers and allow you to read their stored fault codes and do various tests. Replacing the Engine Computer shouldn't affect the operation of the Body Computer or instrument cluster unless it's not sending out some of its data.

Try the old Engine Computer again. If the engine runs better, the new computer may have a problem.

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Tuesday, November 13th, 2012 AT 7:14 AM
Tiny
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I can do that but one problem, when put the old pcm the truck stops dies out and won't start

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Tuesday, November 13th, 2012 AT 7:46 AM
Tiny
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Will it stay running if you hold the gas pedal down a little?

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Tuesday, November 13th, 2012 AT 8:26 AM
Tiny
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No I tried

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Tuesday, November 13th, 2012 AT 9:38 AM
Tiny
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I suppose the stalling could be caused by the old computer, especially if that doesn't happen with the new one, but that sure would not be common.

By the way, how soon does that stalling occur? While driving down the road or within two seconds of starting the engine? If it consistently stalls in two seconds, that's a sign it's in theft mode. Unlock the front door with the key to disarm it.

If it stalls while driving, that is most commonly caused by the crankshaft position sensor or the camshaft position sensor. Usually the Check Engine light will turn on and there will be a diagnostic fault code related to the one with the missing signal. Those codes don't always set during cranking. They are erased too when the computer is unplugged or the battery is disconnected.

Does your vehicle have the factory anti-theft system? If it does not, where did you get the replacement computer from?

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Tuesday, November 13th, 2012 AT 10:11 AM
Tiny
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Not too sure if I have it how do I check. I got the pcm from a web site called auto computer exchange. Why?

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Tuesday, November 13th, 2012 AT 11:04 PM
Tiny
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If there's a "security" light on the dash, or one flashes and the horn honks when you use the remote key fob to lock the doors.

If the vehicle has the factory anti-theft system, you can use any Engine Computer and any Body Computer of the correct part number or application. The anti-theft programming is in both of them. If you install a replacement computer with that same programming, nothing will change. If it doesn't have that programming, it will learn it from the other computer the first time you turn on the ignition switch, then everything will be back to normal.

The potential problem comes in when the vehicle doesn't have that system. Then you MUST install a replacement Engine or Body Computer without that programming. That can be impossible to know with a salvage yard computer because they rarely know which options came on that car, and if they did, that doesn't get recorded on their inventory list. Professional rebuilders may be able to reset that programming but there is no way to do that at the dealership or for you and me. Once the programming has been upgraded to anti-theft, it can't be undone.

If your truck doesn't have anti-theft, and you install a used Engine Computer with it, the Body Computer will learn that programming as soon as you turn on the ignition switch. At that point the engine won't run because both computers are waiting for the disarm signal that's never coming. The typical symptom is the engine will start and run for two seconds, then stall. The only way to solve that is to replace both computers at the same time with ones that don't have the anti-theft programming.

If your engine runs longer than about two seconds, then stalls some time later, that is not a theft system problem. Then the most common causes are the crankshaft position sensor and the camshaft position sensor.

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Wednesday, November 14th, 2012 AT 1:04 AM
Tiny
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The truck has a controll to unlock and lock the car. But the truck would stay on for longer than 2 seconds, than once it feels like it has been warmed up and ready to go it dies out. Its almost as if it runs out of gas but its on afull tank. So thats when we put the new pcm and now doesnt shut off but we still cant get any gauges to work all the lights work but none of the gauges move. But now we put the old pcm in and all the gauges work just fine untill it dies out again than the gauges dont work untill we can get it to start again than they work. As to right now it turns on stays on but no gauges. So I dont understand maybe this pcm has not been updated I was told that the truck is 2002 and was updated in 2004 what does that mean?

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Wednesday, November 14th, 2012 AT 6:26 AM
Tiny
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My best guess is the computer was "flashed" with the latest software. That's like updating Windows on your computer. I wouldn't call it turning it into a 2004 model computer. I'd call it a 2002 computer with the latest 2004 update. You might want to contact the company you got the computer from and tell them the same things about the inoperative gauges. They may have a simple answer or they may exchange the computer.

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Wednesday, November 14th, 2012 AT 6:51 AM

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