I've written about this before and gotten some advice- "BCM bad" or "IOD fuse blown". Various electrical things (door locks, radio, speedo, gas gauge, temp gauge) quit on my 1992 Caravan. Dealer checks came up that it was the BCM (body control module).
I just spent $365 getting the BCM repaired and reprogrammed, and it didn't cure my problem.
I know I'm probably bass ackwards on this- should have checked the IOD fuse first, but I took the dealer's word for it that the BCM was the problem. Maybe they didn't even check the IOD fuse, who knows!?
Now I'd like to check the IOD fuse, but I don't know where it is. Some have indicated it's under the hood, but without a picture, I can't locate it.
Can anyone furnish a pic or a really good description of its location?

 

I'll say it again(I said it in another thread to other people), no manufacturer in the history of auto-manufacturing has made a controller that detects it's own hardware failures(if an analog component or IC dies inside one of these units they simply don't work and everything they control doesn't either). When you see controller based DTCs it's where they detected certain external faults x starts and are designed to 'cripple'. Feel free to ask a MSC engineer who knows the proprietary design specs or maybe even worked on the design x-generations ago.

You'll see the same misinformation around TCM and PCM/ECM issues in the rare case you find a discussion that doesn't just dead end..

EDIT: It's by parking-brake all the way up to 2000. Also, I've seen gritty or lose negative cable cause these exact symptoms; it's because it effects the load. IOD-holding fuse box by battery for 2001-2007, despite what some google searches say.

 

In 1992, there was no IOD fuse. It was a connector off of the battery that you would disconnect if storing the vehicle. It has a red with white tracer wire and a black with red tracer wire in it. Usually close to the battery or on the left fender. I would say not a controller issue just because the things that don't work have no one controller in common.

 

[QUOTE=Tizzy1;3191806]In 1992, there was no IOD fuse. It was a connector off of the battery that you would disconnect if storing the vehicle. It has a red with white tracer wire and a black with red tracer wire in it. Usually close ys it's the BCM, Tizz

 

Must've nudged something on y computer that eliminated a lot of things, including Tizzy's quote.
I'm really confused. Dealer said all these things were caused by BCM, Tizzy says one controller wouldn't be the cause of all the glitches. Others say it might be the IOD, Tizzy says the '92 doesn't have one. Any other comments? I'm really stuck on this. Obviously, I'd like to get everything working again, but also obviously, I don't want to spend a fortune on diagnoses for a car this old.

 

So IF there is an IOD, it's inside the flip down fuse panel at the bottom of the instrument panel near the parking brake? Does it look different from other fuses?

 

In the 1992 model year, there is no IOD fuse. This is not an assumption, I'm a dealer tech that has been here a long time, worked on these when they were new and own one. It is a natural colored connector on the left fender area. Your issues are with the power door locks, (controlled by the BCM), the radio (a stand alone item), and multiple gauges, which the cluster, a module itself, gets the information off the data bus. Speedo from the tranny controller, fuel level from the BCM and coolant temp from the PCM. The only thing that ties them all together is the BCM, Cluster and Radio are all supplied their B+ feed from fuse 3 (20 amp). Maybe start looking there.

 

Unless of course they have the EGH or EGA engine option in which case they do have one. This is like when people insist there are kicker-panel fuses on later gens even though the loaded models only have one panel under the hood and about a dozen 'un-serviceable' fuses.

Also, your topology for BCM is wrong. PCM has always filled RAM with BCM returned data structures after it powers it after ignition closes the 2 PCM b+ circuits..

 

Sucks to be me I guess.

 

Thanks for the info--at least I can stop looking for the IOD. I don't think I have the expertise to go further with this myself, except to check the feed from fuse 3. I guess the beast will have to be driven as is; I'm not about to spend a bunch of $ on search missions for a car this old. If I could be assured I had a knowledgeable mechanic like you, I might feel different, but it's a roll of the dice to take it to just any old dealer. Trusting the last one when they said it was the BCM shows where it gets you; $365 (could easily have been a lot more) down the drain.