Bad ECM

The problem has nothing do part number. Its coded signal relaying between the PCM the central timer module the immobilizer and the keys. The security system is locked up without the VIN specific coded wireless signal ( a constant variation Loop)

There is no way to tell if the unit will work unitl you try and program it.

Hi guys. Sorry Jacobandnickolas for butting in again but I couldn't help myself.

If it runs for two seconds and shuts off, it's in theft mode. Unlock a front door with the key. If the truck doesn't have the factory-installed anti-theft system, the used computer had it programmed in and it taught that programming to the Body Computer. That programming can not be undone. Another used Engine Computer will learn that programming now from the Body Computer as soon as the ignition switch is turned on. You will need to replace the Engine Computer AND the Body Computer at the same time before turning on the ignition switch.

The problem is it's almost impossible to know if a salvage yard computer has that programming because those guys won't know, and there's no way to tell by looking at a vehicle. The only way to know for sure, unless you know the history of the donor vehicle, is to buy a remanufactured computer from the dealer.

This is all irrelevant if your truck came with the factory anti-theft system. Any used Engine Computer and any used Body Computer will work and will upgrade to the anti-theft programming automatically if it isn't already, but from then on those computers must only be transplanted into another vehicle with the anti-theft system.

You would know if your vehicle had anti-theft. The horn is set to chirp by default when you lock the doors with the key fob and there's a red "security" light on the dash. The running lights would flash and the horn would pulse if you opened a door through an open window without unlocking a front door with the key or the remote key fob.

I am aware that the same Engine Computer will work on a 2.7L and 3.5L in an Intrepid but you can't assume anything when going to a different year or engine size. The only way to know a computer will work in place of your original one is if they're both the same part number. That doesn't mean they HAVE to be the same number. Every time a computer gets an upgrade, a modification, or has any slightly significant change it gets a new part number or it will have an "A", "AA", "AB", or something like that on the end.

You order parts from the dealer by application but when look it up they order from the parts depot by part number. The people picking the parts don't ask or care about the vehicle it's going into. Knowing that, the dealer can look up an Engine Computer for your truck and the one the donor computer came from, and if they both call for the same replacement part number they will interchange. Another way of saying it is if both your old and new computers were sent in to be rebuilt, they both would come back with new part numbers and they would be the same.

I should also clarify my story about the Engine Computer or the Body Computer teaching the anti-theft programming to the other one. A coworker ran into that on an early '90s Dynasty. Watching him diagnose the no-start condition was how we learned about this. The next one involved a '94 Intrepid donated to my community college Automotive program by Chrysler after it was used to test-run a new assembly line. A student damaged the Engine Computer and we had a no-start with two replacement computers. We needed to find both computers with no anti-theft programming. The third one happened to a friend who owns a body shop and specializes in rebuilding one and two-year-old smashed Chrysler products. He finished a Neon and just needed to replace the broken Engine Computer. To be able to test-drive the car he borrowed the computer from a friend's car. It ran fine but the rebuilt car had anti-theft and it upgraded the programming in the borrowed computer so it no longer worked in the original car.

I've warned other people about how replacing a computer could cause the no-start condition but those are the only three examples I can site. I haven't heard of that happening on a Durango or any other models, but I'd rather NOT hear about it If this information could avoid that headache.

What was wrong with the original Engine Computer to make you want to replace it? If you can stick it back in and the engine starts and continues to run, you will know the new computer did not upgrade the programming in your Body Computer, (Central Timer Module - CTM). That would imply instead the replacement computer is not compatible and is not getting the "fuel on" or "run" command from the Body Computer.

The dealer can call into Chrysler on their "DIAL" system to obtain vehicle information. I'm pretty sure they can do that for all the cars, not just the ones they sold new. The list of options will tell them if anti-theft was included.

Shutting down after two seconds is how it acts when it's in theft mode, but that proves the computer can run the injectors and ignition coils. What we don't know about a computer from a different size engine is if the injectors will spray the right amount of fuel. Fuel volume is based on intake manifold vacuum, fuel pressure and injector nozzle size which you didn't change, and length of time the injectors are held open and their timing. Those two things could be different. If the larger engine uses larger injectors both computers might hold the injectors open same number of milliseconds. However, if both engines use the same size injectors the larger one needs them held open longer to deliver the right amount of fuel. The computer can only adjust fuel metering plus or minus about ten percent beyond the factory programmed values that form the starting point. If the engine idles smoothly with no black smoke, and there's no stumble or hesitation on acceleration, and the Check Engine light doesn't come on indicating a rich or lean condition, the computer can be assumed to work in that application.

Hi Guys

What he said is correct. It does sound like an anti theft system causing the problem. However, from experience, I have found that you need to have the exact same part number when changing the ECM. I think you will find that if you get the correct one, the problem will go away.

Great and wondrous news! I just got off the phone with my buddy and first I have to correct my story about the Neon. That one simply needed the four-digit PIN number re-entered and he used my Chrysler DRB3 scanner to do that. No different computers were needed and that one did not teach anything to the Body Computer.

The dealer can't tell if an Engine Computer has the anti-theft programming just by looking at the part number. They all start out without that programming and there's nothing visual to tell if it got stuck into a vehicle with the anti-theft system.

He said the 2002 Durango does not self-program to the anti-theft programming and you can use any used computer. There's "gazzillions" of them in the salvage yards. Just pop one in and it will work, however, one from a 4.7L will not work. I'm pretty sure once the engine stalls, if you do not turn the ignition switch back off and on, and you just crank the engine again, you will still have spark but no fuel pressure. I could be wrong about the spark but the fuel pump always runs for one second after turning on the ignition switch. That's where the pressure comes from to let the engine run for two seconds. After that the fuel pump is supposed to turn back on when the engine is rotating, (cranking or running). That is what does not happen when it's in theft mode. The fuel pump relay will be listed on the scanner as "denied", "off", "no", "theft", or something like that.

It depends too on the model. On some the anti-theft system turns off just the fuel pump relay so with those you'll still have spark during cranking. On some they turn off the automatic shutdown (ASD) relay. That removes power to the ignition coil(s), injectors, a few other things, and the fuel pump relay. Those will have no spark during cranking.

Which way your truck works is irrelevant because we know the ignition system is working and the computer has control over it. We know the fuel pump is working because the engine will run for two seconds until the pressure runs out. Based on that we know the pump is not continuing to run beyond that one-second burst.

I installed a lot of real-world electrical "bugs" for my kids to diagnose and one of them was an open voltage regulator inside the Engine Computer on that '94 Intrepid. As a former tv repairman I'm very accustomed to working on circuit boards that have copper traces on both sides. To install the wires to run to a switch that allows me to insert and remove the defects, I drilled a hole through the circuit board where there was no copper on either side, then ended up with one injector not firing. Come to find out there is a third layer of copper and maybe a fourth sandwiched in the middle of the board, ... And I drilled right through the circuit for one injector. Your mechanic may have run into the same thing. He may have soldered the loose pin on both sides of the board but it didn't catch the inner layer. You would have to remove any protective jelly from the area, then hold the board up to the light to try to see the outline of another circuit, then follow it to a component that is accessible that you can attach a jumper wire to. Car radio service manuals have drawings of the circuits on both sides of the boards so you can figure out where to hook jumpers, but no one makes service manuals available for computers.

At any rate, it sounds like you just need the right computer. For what its' worth, the pins on computers are really tough. I would sooner suspect a stretched terminal in the connector. My school also had a '97 Dakota donated by Chrysler after one of their trainers got done with it, and I pulled the Engine Computer connectors apart a few times. If you have three separate plugs like mine did, those can be real frustrating to get back together. I probably did something wrong but I had to cut about two dozen short pieces of mechanic's wire and insert one into each terminal to guide them into the connector housing. If your new computer acts the same way, with intermittent operation, suspect a terminal in the connector.

As a final point of interest, if you're anywhere between Ohio and southern Georgia, do a search for "Pull-A-Part" and see if they have a yard near you. You pay your buck, throw your tool box in one of their wheel barrows, and you can spend all day there. They are all very clean and well-organized. Employees and customers are real friendly, and parts are inexpensive. My list is a few years old but a computer is listed at $31.89 with a warranty. A 2002 model might be a little new for them but it's worth looking. You can check on their web site which yards have trucks like yours but they can't tell you engine sizes, optional equipment, or what has already been removed or damaged.

No PIN number. That's for Neons.

It is unlikely you will find the same part number because so many changes occur and each one gets a new number. Just go by application. Pop it in and it should work.

You're into stuff I can't answer now. Years ago California required additional systems on cars sold there that required the Engine Computer to be able to control them so they were different. Today most of the rest of the country has equally stringent regulations so those systems are already in use and the only difference in computers is some internal programming. Some engines from the early 2000s didn't have EGR valves so the computers for the 49 states would not have built-in monitors for that. I would avoid a computer from a California truck if you aren't in that state.

According to my friend who rebuilds smashed Chrysler products, he has never concerned himself with part numbers. He buys front clips for the body parts, then saves things like wire harnesses and computers to replace those that are smashed from a crash. He says if it came from a 2002 Durango, it will work in a 2002 Durango. As far as working on or from a truck, you would have to compare the connectors. If they're different in size, shape, location of key ways, or number of wires, they were made different for a reason and they won't interchange. If the plugs are the same there was no reason to make them different because there was no reason to worry about someone plugging in the wrong one. Still, if I was working on it I would want to compare the charts in the service manuals. The full-size trucks are different than the Dakotas so they will have different service manuals. The Durango is based on the Dakota but they still each have their own service manuals. You would have to go down the list in each manual, one for your truck and one for the donor vehicle, and look at the diagrams for the proper engine sizes, to see if the wire locations and functions are the same. If they are I would have no worries about plugging it in.

Do an internet search for "Pull-A-Part" and see if they have a yard near you. They have 23 between Ohio and southern Georgia. I've been to 16 of them. All are very clean and well-organized, employees and customers are real friendly, and parts are inexpensive. You pay your buck, throw your tool box in one of their wheel barrows, and you can spend all day there. A 2002 model is right on the edge of what they will typically have in their yards because they don't buy insurance wrecks. They only have what people bring in. My list is a few years old but they were charging $32.00 for a computer, ... Less if you didn't want a warranty.

I don't know how this got overlooked but I'm sorry I didn't reply sooner. When you replace a computer with the four-digit pin number, you connect the Chrysler DRB3 scanner to retrieve the number from the old computer, then install that number into the new computer. If you no longer have the old computer, the dealer's parts department can get it for you. I'm on very good terms with the one I used to work for so they do that for me for free. Most dealers will not do that for people they don't know because it's a security-related code number. They will want the vehicle and often some type of proof of ownership.

Happy to hear it's solved. Don't be too hard on that last mechanic. He reached the logical conclusion based on what he knew. There is nothing that can happen to the ABS Computer to make it lose its programming. Disconnecting the battery and changing other parts won't affect it. For that reason, when tire size is wrong, and especially when axle ratio is also wrong, he has to suspect someone changed those settings or the computer has a problem. He knows that if someone changed the settings, they knew what they were doing and they would have set them correctly. If you came in with the ABS light on right after changing tires, you would have told them that, and re-programming is the first thing he would have looked at. Since he was of the impression nothing had changed recently, the computer would be his first suspect.