Well, we know you'll argue with anyone who disagrees with you. In this case the diagrams are right but the description is misleading. I helped a friend rebuild a smashed '06 dually diesel three years ago. He had it shipped from Salt Lake City to Wisconsin not realizing it had a 6-speed manual transmission but it has turned out to be a dandy vehicle and now he doesn't want to put it up for sale. It was hit so hard the engine was pushed back over a foot and the firewall was destroyed. My job was to modify the replacement heater box to make it a dual zone, (another gimmick), do some engine work to replace the power steering pump bracket, help with the frame straightening and firewall replacement, and replace the crushed connectors for the Integrated Power Module.
Contrary to what you believe about that module, it is full of electronics and is accessed by the scanner just like an Engine or Body Computer. The reason I know how this one works is when the truck was completed, it had no backup lights, no motorized pedals, and no 4wd lights on the dash. There is no relay anywhere for the backup lights, ... Until I added one. The switching is done electronically, and that is always less reliable than a simple mechanical switch. By testing the circuit is how I know that is a 5 volt signal that gets grounded out by the backup light switch. That is a standard computer sensor voltage. Those circuits need to have a supply voltage that is higher than what they're using for sensing so they can't work with 12 volts. Only a mechanical switch can work with any voltage.
The way it sounds like you think it grounds a relay would make perfect sense but relays can be easily replaced and they can be removed to perform electrical checks. Those are two things all car designers seem to want to avoid. All you can do is verify there's five volts at the switch, and the switch is grounding it to 0 volts. As I recall, there isn't even a dedicated fuse for the backup lights. If the switch tests pass and there's no 12 volts coming out for the lights, you're done. All you can do is order a new module. I suppose $800.00 is peanuts for some people but I'd sure rather own vehicles like mine that use a pretty reliable 15-dollar switch. When it comes to computer-controlled backup lights, what benefit has anyone seen or what do those vehicles do that mine doesn't?
Believe me I tried everything to make that module work so the truck would pass inspection. As a temporary measure, I wired in one relay to switch on the backup lights, and another to supply the voltage to the movable pedals when the ignition switch was on. There was no way to make the 4wd lights work because they were a part of the instrument cluster which is another unreliable computer. It required a computer signal from the data buss, and that wasn't coming. This might be one place where a computer circuit is more reliable than the troublesome 4wd switches of the past that got moisture in them, but those old switches were a lot easier and cheaper to replace.
Luckily the inspector didn't see the inoperative 4wd lights, but everything else worked to pass the inspection. Once the new IPM arrived and was installed, those lights and the other two functions worked fine but that was $800.00 my buddy hadn't planned on spending.
To be fair, the truck I helped with has a manual transmission so I never read about the range switch on automatics. Regardless, if you look at the diagram, it is still just a switch that grounds the same pin at the module so the operation should be the same. These circuits might work properly most of the time but so did simple switches. Explain the benefits of computer circuits to the owner as you hand him the estimate for repairs.
Just got done last week helping him with another '06 diesel with intermittent power locks. All remote, manual, and speed-related functions would go dead in cold weather. We got them to work by setting the truck outside, then heating the IPM with a hair drier. I have no idea how involving that computer in running door locks is an improvement over simple switches. Of course one press on the remote opens just the driver's door, and another press opens all four doors. I wonder if the owner of that truck thinks that feature is worth $800.00.
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Tuesday, January 1st, 2013 AT 2:12 AM
