If I may interject one comment of value, the Check Engine light can have nothing to do with reading diagnostic fault codes, so you were told wrong. First, there can be well over 2,000 potential fault codes in the Engine Computer. Only about half of them refer to things that could adversely affect emissions. Those are the codes that turn on the Check Engine light. You can get an idea of the severity of the code by how the light acts. With intermittent problems that are relatively minor, if the defect goes away while you're driving, the light will turn off. If it's a little more severe, once the light turns on, it will "latch" on until the ignition switch is turned off, even if the defect has gone away. Still more severe codes will turn the Check Engine light on any time the ignition switch is on, even if the problem has stopped occurring. For those problems, the light will only turn off if the code is erased, or on most models after the engine has been restarted a certain number of times, typically 50 restarts.
The most serious codes are set when too much unburned fuel is going into the exhaust system, such as with a spark-related misfire. That fuel will burn in the catalytic converter, overheating and damaging it. The Check Engine light will flash for those codes while the problem is being detected. If that continues, you're supposed to stop the engine as soon as possible to avoid damaging the expensive catalytic converter.
For the other 1,000 or so fault codes that don't refer to emissions, the Check Engine light doesn't turn on, but the codes can still be read. The goal is to not disconnect a battery cable, run the battery dead, or erase the codes with a scanner until they've been read, otherwise that valuable information will be lost. Those codes also never ever say to replace parts or that one is defective. The people at most auto parts stores will read those codes for you for free, but their intent is to sell you parts. When a part is referenced in a fault code, it is only the cause of that code about half of the time. First we have to rule out wiring and connector terminal problems, and mechanical problems associated with that part, before we spend a customer's money on a new part.
To say that a different way, if the Check Engine light has turned on while driving, even briefly, there IS at least one fault code in the Engine Computer. If the Check Engine light has never turned on while you're driving, there COULD be a fault code in that computer.
The other problem here is when you have fault codes read at the auto parts stores, they usually use a very low-cost code reader that can only access the Engine Computer. Some of the more advanced code readers can access Anti-lock Brake Computers and Air Bag Computers now, but there are two or three dozen additional computers on today's vehicles. The CAN Buss system is newer than what's used on your car, but there is still a data buss that connects all the computers together. This is what you were referred to for having the entire car scanned for fault codes. The real expensive scanners will talk to every computer and list all of the fault codes it finds. Engine running problems are detected by the Engine Computer which uses the Check Engine light to tell you there's a problem. The Air Bag Computer uses the "SRS" or "Service Supplemental Restraint System" light to tell you there's a problem in that system. The yellow "ABS" light is used by the Anti-lock Brake Computer.
All of those lights should turn on from one to six seconds each time you start the engine, as a bulb check during each systems' self-check at start-up. Power windows and door locks are controlled by the Body Computer. There is no dash light related to the Body Computer, so all you can do is read the codes in that computer. Again, all of that has nothing to do with the Check Engine light not being on.
As an additional hint, keep in mind computers are very intolerant of low system voltage. Computers will start to shut down or do weird things if the charging system isn't developing between 13.75 and 14.75 volts. You can check that very quickly with an inexpensive voltmeter while the engine is running:
https://www.2carpros.com/articles/how-to-check-a-car-alternator
A problem with the charging system should turn on the Check Engine light, but often not right away. A fault code for "low system voltage" will set in multiple computers, but the Engine Computer will see that as a possible inability to run the injectors and ignition coils properly, which will lead to increased emissions. To further complicate the issue, there is always a long list of conditions that must be met for a fault code to set. One of those conditions is certain other codes can't already be set. Once the Engine Computer sees low system voltage, for example, it will likely suspend many of the tests it constantly runs on injector and ignition coil performance. Setting those codes would only make the diagnosis more confusing.
Computers for safety-related systems like air bag, ABS, engine, will always have at least two 12-volt power feeds, so even if they do weird things due to low system voltage, or if a fuse blows for one of them, the other 12-volt supply is there to run the warning lamp on the dash.
I'm pretty sure MIKE H R and JACOBANDNICKOLAS were going to get to checking system voltage. I just beat 'em to it. My reason for sticking my nose in here is I couldn't let the Check Engine light comment go uncorrected. Too many people, including even some experienced mechanics, have the false misunderstanding that there's no fault codes if the light isn't on. That can lead to a lot of frustration among car owners, and makes a diagnosis really difficult or impossible. I've heard mechanics tell car owners to "keep driving the car until the light turns on, then we will be able to diagnose it". Truth is, continuing to drive with some defects leads to other, much more expensive parts failing. That could be avoided with a proper diagnosis right away.
I should also clarify the Transmission Computer can also detect problems and set fault codes, and this is the only one that can ask the Engine Computer to turn on the Check Engine light. The code in the Engine Computer will be code "P0700" which just means there are other codes that need to be read in the Transmission Computer. That is done because slippage or incorrect gear operation in the transmission leads to using more fuel which leads to increased emissions.
The CAN Buss system is a totally new language the dozens of computers use to talk back and forth to each other. It is faster and more comprehensive than the older "OBD2", (on-board diagnostics version 2) emissions system that everyone switched to starting with '96 models. Chrysler's first vehicles to use the CAN Buss system were the Dakota and Durango in 2004. That last models to switch over were some Jeep models in 2008. Chrysler's DRB3 scanner works on all Chrysler models from 1983 through the years with OBD2 systems, including emissions systems on all car brands, but not on the newer CAN Bus systems. The better aftermarket scanners can work on all of those systems.
I'll be waiting to see what you find and what it takes to solve this.
Thursday, September 22nd, 2022 AT 1:51 PM
