Engine swap

2004 is the first year Chrysler's DRB3 scanner became obsolete, but only on the Dakota / Durango. That's because those models were the first Chrysler products to switch over to the current "CAN Buss" computer language. A 2003 computer is totally different from a 2004 computer. This is also when most sensors and switches become little electronic modules that talk back and forth with the computers. As such, while the basic engine might interchange, you would need to keep all the 2004 sensors and wiring harnesses with the 2004 truck. Everything on the 2003 engine can not be used.

Also be aware a lot of do-it-yourselfers run into a frustrating problem with the flywheel or torque converter. There's a ring on it with notches cut out that are detected by the crankshaft position sensor. The number and spacing of those notches is different depending on the model year and engine size. There will be four sets of notches for a V-8 engine. Some have four notches or three notches for each set. Some will have four notches, four notches, four notches, then three notches. The set of three is how the computer knows which pair of cylinders is coming up on top dead center, then it knows which ignition coil to fire. If you use the flywheel that came with the donor engine, there's a real good chance you'll have a crank / no-start condition.

Also be aware that with so many other differences in with the CAN Buss system, a lot of additional things are monitored by the computers, so you can expect to find related differences with the engine. The best example is missing vacuum ports in the intake manifold. There may also be missing ports or attaching points for sensors and solenoids. I ran into this years ago when replacing the high-mileage engine in my '88 Grand Caravan. The dealer I worked for gave me an '89 engine from a crashed Dynasty. That one was missing the threaded hole for an intake air temperature sensor in the intake manifold.

Consider too that the donor vehicle could have been built in late 2003, but be a 2004 model. You can tell that by the date shown on the emissions sticker under the hood. Some engines had EGR valves, and some didn't. Things like that are not necessarily year-specific. You can run into these kinds of differences with two engines from the same year. If you look up the long block part numbers on an auto parts site like for Rock Auto, you'll see some suppliers list the same number for both years, and some have different numbers, along with a long list of variables you need to match to your old engine.

Engine Computer part numbers will be real confusing. At first there were likely only two or three different numbers to cover a number of variables. The majority of lesser variables are handled by modifying the software installed in the computer on the assembly line. Later, there will be updates to take care of minor performance or emissions issues, and if they start to see the same failures in computers sent back for repair, they will use beefed-up parts to address that. Any software updates or reliability improvements warrants a new part number. That could be as simple as the "AC" at the end of the part number being replaced with an "AD", or a step higher. Major changes get the computer a totally different part number, which will work in a vehicle that has a computer with the older part number. This is another time when you need to stick with the computer in your truck. Don't transplant the computer from the 2003 truck.

The same applies when the two computers have the same part number. The mid 2000s is when they were just getting into programmable computers so they didn't have to produce so many variations. Ten computers with the same part number can have ten different software versions, but only one is correct for your truck.

That's the basic engine block that stayed the same for many years. You have to consider all the variables with the bolted-on stuff. If those are the same, that would be wonderful. If there's differences, you'll be the one stuck trying to figure them out.

As I described earlier, if the block and intake manifold have the same ports for sensors and switches, you just transfer those from the old engine to the new one. If the new engine has extra ports, just plug them. If the old engine uses an EGR valve and the new one didn't, you could end up switching the intake manifold and/or cylinder heads. If you try to use a sensor that is on the new engine, if it is the same, the connector will be the same. Those have little "keys" molded in to prevent you from being able to connect the wrong plug to something. From the outside, those connectors can look the same, but if one doesn't go in easily, don't try to defeat those keys. You'll be inserting more variables that could defy logical diagnosis. Go through the work on installing the part from the old engine instead.

I would look closely at the engine you're going to get, even take a lot of photos, then compare them to your current engine. Chrysler has a well-known history of very good parts interchangeability between many models and years, but the politicians keep on adding on more and more regulations, and changes to the emissions rules, so many of the differences now are to try to meet all those new rules. Today a lot of things change every year.