IOD fuses have been around since the early '90s. Before that, we had large wires near the battery with bullet connectors that allowed them to be unplugged. You're right about their purpose. Unneeded accessories that are run by computers that have memory circuits that constantly draw standby current are disabled, but certain safety systems, like power mirrors, will still work only while the engine is running. They get powered up by the alternator and allow the delivery truck driver to operate things needed to do his job.
The TIPM is a computer module incorporated into the under-hood fuse box, and in my opinion, adds an unnecessary level of complexity where it is not needed. I left the dealership before those showed up, so I never worked with them there. I have worked on a few at my buddy's body shop. What I DO know about them I learned from the former head of Chrysler training for all of Wisconsin. She used to use my classroom as one of her three remote training sites, and I was allowed to sit in on those classes. (She was a REAL good instructor, and is where I learned some of my wondrous teaching skills).
Anyhow, getting back to the point, Chrysler was the first manufacturer to use a computer to run an engine, back in the mid '70s. There were only a few variations and the systems were real basic, compared to what we have today. When GM started using computers, there were quite a few variations, depending on the engine, year, and optional equipment. Chrysler had a different computer part number specific to each application. That made it impractical for a dealer's parts department to stock every one. Instead, they had to order them as they were needed. Fortunately their failure rate was extremely low. GM went a different route that made more sense. They only had a few computers that covered almost all applications, then they plugged in the "PROM", (programmable read-only memory), specific to the application, to give the computer its personality, so to speak. They had a very high computer failure rate in the late '80s to early 90s, but you could use almost any replacement then just transfer the PROM to it. No one had to stock a big bunch of different computers.
That has been taken to a new level now with downloading software into a new computer. GM, in my opinion, is the innovator at coming up with stuff that benefits them at the expense of their customers, and this was one of them. Unfortunately, everyone else seems to copy new ideas within a few years, and this is where your new TIPM is finally related to my wondrous story. The new TIPM will work on many years, engines, and models with a variety of optional equipment. The software has to be downloaded specific to the vehicle, and on some applications that can only be done once. GM did that so you can't buy a used computer from a salvage yard. You have to buy a new one from their dealers, and you have to pay them to install the software. That is one of their "customer-unfriendly" business practices.
I don't know if that one attempt applies to your new TIPM, but if it does, during the download process, the computer goes out and looks at the vehicle's circuitry and tries to talk with the other computers. If, for example, it doesn't find an Anti-Lock Brake Computer, it will know that option isn't there, and it won't include software for it in the download. To do so would cause it to set diagnostic fault codes later when it can't find things during the self-tests it runs. The point is, you need to have everything installed and connected, so the computer can detect everything and ask for the necessary software to be included in the download. That could be why they don't want to get the radio or interior lights working until the amp is installed. I should mention too, that starting with a few 2004 models, the industry changed over to the current "CAN-BUSS" computer system that standardizes a lot of stuff, and it adds a huge amount of complexity to the electrical system. What used to be a simple, reliable door switch, head light switch, cruise control switch, etc, are now a tiny computer modules. The manufacturers tells us that makes diagnosis much easier because we can read fault codes that tell us where to start looking, but those little computer-infested parts CAUSE more problems than they solve. Also, people like me can no longer buy the same testers the dealers have to buy, so I, as a mechanic and electrical expert, have to take my car to the dealer for many repairs that I should be able to do myself. That is the main reason I have resisted buying a newer car.
Wednesday, November 30th, 2016 AT 7:12 PM
