Idling high and trouble codes 12, 24 and 55?

24 - Throttle position sensor voltage high/low.

Code 12 just sets because the ignition switch was turned off. Code 55 means it's done displaying codes.

The throttle position sensor is fed with 5.0 volts and 0.2 volts, then the center terminal is connected to the movable contact that picks off the signal voltage between them, but there are mechanical stops inside it that limit the range of that signal voltage. The acceptable range is from roughly 0.5 to 4.5 volts, give or take a little, from idle to wide-open-throttle. If there's a break in the ground circuit, either inside the sensor, between its mating connector terminals, or that wire, you'll see the full 5.0 volts on the signal wire. That's outside the acceptable range and will set this code.

Likewise, if there's a break in the 5.0-volt feed wire, you'll find 0.2 volts on the signal wire, also outside the acceptable range. That will also set code 24.

The place to start now is with voltage readings at the throttle position sensor, but those must be taken with the sensor plugged in to be valid. The sensor is on the driver's side of the throttle body. That's shown in the second drawing. It's easier to see in the expanded section in the third drawing. Back-probe through the rubber weather seals alongside each wire. The ignition switch must be in "run". If you aren't familiar with using a digital voltmeter, look at this article first:

https://www.2carpros.com/articles/how-to-use-a-voltmeter

They're using an auto-ranging meter here. That's an expensive option you don't need. You can find a perfectly fine meter at Harbor Freight Tools for around $7.00. Also look at Walmart, any hardware store or any auto parts store. If you need help setting it up, I can help with that.

First check for the 5.0 volts and ground wires. If those are both correct, check the middle wire in the connector. Those will tell us where to go next. The voltage on that middle wire should go up to around 4.5 volts smoothly as you open the throttle.

Let me know what you find on those three wires.

I've never looked for those and it is irrelevant. One is for the 5.0-volt supply. That wire and splice feeds at least three or four other sensors. If there was a problem with that wire or splice, you'd have fault codes for all of those sensors. Also, you'd be missing the 5.0 volts to the TPS. That's why we need to know those three voltages.

Same for the other splice. That's for the ground wire, commonly referred to as the "sensor return". It's the ground circuit for those same three or four other sensors, and again, a defect in that circuit or splice would result in fault codes for all of those other sensors.

Both of those splices are buried inside a large harness. They're not practical for use as test points. I haven't found the location of them yet. They're in the paper service manuals, but I haven't found them in the online manuals.

Nope. You only have to find the break and make the repair there. Running back to the splice would usually be extremely difficult and time-consuming. That would not be in the best interest of our customers. You CAN do it that way, but there's more important things to consider. The biggest issue is when there's a wire shorted to ground someplace and a fuse is blowing. A lot of people will cut the offending wire at both ends, then tie in an entirely new piece of wire, thus eliminating the short. That was never an acceptable repair for my students. It will get that circuit working again, but the question is, why did a short occur on that wire? I required my people to follow that wire until they found exactly where the short had occurred, because wires always run in a bundle, or harness, and how long will it be before another wire in that harness develops the same short? This is common when a harness has fallen down onto hot exhaust parts, is draped across the sharp edge of a metal bracket, or in the case of some GM models, the harness runs under the carpet under the driver's feet, and has been sliding back and forth for years. By finding the location of the short, you are forced to inspect all the other wires in that area, and remedy the cause before it occurs on the next wire. That next wire could disable the electric fuel pump, ... On a late Saturday night, ... When the wife is all alone, ... In the country, ... In freezing weather. You can be sure we're going to hear about that from her angry husband, especially when finding the first problem would have given us a chance to prevent the next one.

That said, you're jumping ahead and you're assuming there is going to be a broken wire buried in a harness. While that is a possibility, lets concentrate on the more common causes first. Those are a break, or an intermittent break inside the sensor itself, and a weak connection between a pair of mating terminals in the three-wire TPS connector. The three voltage readings will tell us if we have to look in a different direction.

You got us going down the right path with the signal wire voltage, but you need to list specific voltages. The acceptable range for sensors of this type is from 0.5 to 4.5 volts, corresponding to idle and wide-open-throttle. Those values are for training purposes. In actual practice you may find 0.42 and 4.27 volts, for example. The point is you'll never see close to 0.0 volts or 5.0 volts. When you do, there's a defect and that is what sets the fault code.

Assuming you are indeed finding very close to 5.0 volts on the signal wire, that is going to set the code, and there's no mystery, (or frustration), involved in figuring this out. There's two ways this defect can occur. First let me approach this from a different angle and imagine we lost the 5.0 volt supply to the sensor. Then it becomes rather easy to see with no voltage, there will be no voltage anywhere related to that sensor. The entire circuit is dead and there's 0 volts on every terminal / wire. What's not so easy to visualize is when there's a missing ground circuit. Without going into all kinds of electrical theory, you'll have 5.0 volts all over, including on the ground wire all the way up to the break. You'll have 5.0 volts at every point along the sensor, regardless of actual throttle position. That's the 5.0 volts that's outside the acceptable range and what triggers the fault code. There isn't a lot of ground wire to check. The break has to be before or up to the splice. Remember, four or five other sensors use that same ground wire, and they aren't setting fault codes, so the part they have in common has to be okay.

The second way this can happen is a little trickier to understand, even for experienced electrical experts. That's when there's a break in the signal wire. The best clue here is when you take the voltage readings at the sensor, you'll find the nice smooth sweep from 0.5 to 4.5 volts as you work the throttle from idle to wide-open-throttle, (and you'll bang your head against the wall because the voltage sweep looks perfect, yet you keep getting that stupid fault code, but if you look at live data on a scanner, you'll see what the computer is seeing, and that is 5.0 volts. With the break in the signal wire, what you see at the sensor is not the same as what the computer is seeing. I'll give you the explanation, but you won't be tested on this later. Inside the computer, that signal wire is interconnected with all kinds of other circuitry. Because of that, when there's a break in that wire, the voltage that shows up and is seen by the computer can "float" to some random value. If, by chance, that random voltage was to remain between 0.5 and 4.5 volts, the computer would accept it and try to run on it. There would be no fault code to direct you to the circuit that needs further diagnosis, and symptoms would be from mild to miserable with a very elusive solution. To prevent that, all computer sensor circuits use a "pull-up resistor" or a "pull-down resistor". Many import models use pull-down resistors. Most domestic models use pull-up resistors. That is a resistor of such high value, it has absolutely no effect on a properly working circuit. You'd never know it's there. That is, until you get that break in the signal wire. That is when that pull-up resistor, which is tied to the regulated 5.0-volt supply, places 5.0 volts on the signal wire's circuit inside the computer. That forces a defective condition to be detected, the computer sets the fault code, and you know exactly which circuit needs to be diagnosed.

When a pull-down resistor is used by the manufacturer, when a break occurs in the signal wire, that resistor is tied to ground. Again, if the circuit is working properly, no one even knows that resistor is in there. When the break occurs, 0.0 volts is placed on the signal wire, which is the other defective condition. On newer models, the fault codes get a real lot more specific. It will state whether the signal voltage is too high or too low. Yours has to be determined with the voltage reading you took.

Now what I want you to do is see exactly what all three voltages are. Do it that way because then there's no confusion over wire colors or whether you measured on the right one. Once I know those, this can again become a little confusing because it's an issue of it's rather easy to do, but difficult to explain. Instead of confusing you with a list of possible tests, we'll stick with just what applies to your car.

Remember, these readings are only valid when you leave the TPS plug connected and you back-probe through the weather seals alongside the wires. If you unplug the connector, you WILL have an open circuit, (break in the circuit), You run the risk of introducing a different, second problem.

If you have access to a scanner, let me know. Also, some of the very inexpensive code readers are sophisticated enough to give sensor data. I have a few and found they update their readings painfully slowly, but with this problem, they can be just what is needed to see what the computer is seeing, then we can compare that to what you find at the sensor.

You're right. All OBD2 plugs must be under or near the steering column. Most '95 and older Chrysler plugs are under the hood on the driver's side. On a few models it was on the passenger side. '89 was the first year for the 4-speed transmission in Caravans. That computer used a different plug under the center of the dash, usually on the right side, and often behind a small pop-off cover. It will be blue. That's also the plug for Air Bag Computers. If you have anti-lock brakes, as I recall, the module and / or the connector is in / behind the glove box. For ABS in the early years on Dakotas, no other scanner works on that system other than the Chrysler scanners. I guess the aftermarket scanner manufacturers felt there wasn't much call for that.

I just found that I had the diagnostic connector saved for a '92 Dakota, and it is indeed on the passenger side. Check out the two drawings.

I can recommend two scanners and you are likely to find them on eBay. One is Chrysler's DRB2. It requires a plug-in cartridge. There were probably dozens of them for all different years and models, but by '93, for my '93 Dynasty, the cartridge label was blue to match the color of the service manual covers for that year, and the cartridge incorporated all the previous cartridges into that one. Look for a cartridge with a yellow label, corresponding to the service manuals for '94. That was the last cartridge produced. It covers all the previous years and models, and it is the only one there is for '95 models. Nothing changed on the vehicles from '94 to '95. I have one of these. The advantage back then was manufacturer scanners always do everything you need, and aftermarket scanners never do quite as much.

I also have a Monitor 4000. It uses a plug-in cartridge too but it's different from those for the DRB2. Everything is similar because both were made by OTC, Owatonna Tool Company. One uses a 4 x 5 keypad and the other uses a 5 x 4 keypad. One advantage to the Monitor 4000 is one cartridge works on GM, Ford, and Chrysler models, but as I said, there might be a few things missing. This one had a new cartridge every year, but I don't know how long they supported it. It can't work on '96 or newer OBD2 vehicles, so I suspect if there's a '95 cartridge, it's the last year for them. My cartridge goes up to '92 models. I found a separate Anti-Lock Brake cartridge, but I never plugged it in to try it. Don't know if it will work on a Dakota.

Part of the deal when I bought this scanner was they included an adapter module and the cable to work on Chrysler's new computer-controlled transmission. That came out in '89. Didn't use that much at the dealership because I didn't get involved much with transmissions. I originally bought it so I didn't have to wait in line to use the dealer's only scanner.

If you want to make a major step up, look on eBay for Chrysler's newer DRB3, but expect to spend around $2000.00. The people at the parts department where I used to work made me a good deal on four of them. I sold three on Ebay and made enough to pay for the one I kept. On the web site, the manufacturer sold the kit for over $6200.00 with a lot of cables and adapters you're not likely to ever need. Depending on the year they were made, they work on either '96 and newer models or '98 and newer models directly, then there's extra plug-in cards you can add if you want to. There are a few specialty cards for the Crossfire and for the Sprinter, but the popular cards were called "Supercards". The Supercard 1, (white label), allowed the scanner to work on all Chrysler models, other than those few specialty models, back to '83 models and up to '93 models. The Supercard 2, (yellow label) allowed it to work on '94 through '97 models, but it also allowed it to do oscilloscope and transmission pressure functions with the connectors in the kit, and it allowed you to do emissions-related work on any brand of vehicle sold in the U.S. Starting with '96 models. For that reason, a lot of independent shops bought them. The first year they went obsolete was on the 2004 Dakota / Durango. The last year they worked was on a few 2008 Jeep models. If you ask around at some local shops, you might find a dusty one on the shelf. Most shop owners would be happy to sell theirs as they've already invested in something newer.

I have a 2014 Ram now and recently bought a 2014 Caravan. For those I have a Snap-on Solus edge. Snapon is very proud of their annual software updates and charge around $1000.00 for them. You can't skip any years, but that can work to your advantage. I bought mine in 2018 with the latest update at that time. The fellow is out of IL and always has a few listed on eBay. Being four years out of date now, I would have to buy the 2019 update before I could buy the 2020 update, etc. It would cost around $4000.00 to bring it current. That's silly because a new model only costs $4000.00. You have to pay extra for Asian import coverage and extra for European coverage, but you're still better off, if you don't need the latest years, to buy an out-of-date model. You can find these on eBay too. I recently saw a couple for around $700.00 updated through 2014 models. This scanner will work on all models but for '95 and older, you need the cable adapters specific to each manufacturer. You'll find those on eBay too. I bought the European set for around $50.00. Other individual adapters run around ten dollars each, and even less in some cases.