Help request: Main Body ECU schematic?

What readings did you get?

The "inner circuit" of the junction block that the body ECU sits in is published in the Electrical Wiring Diagram. That's enough to see the LIN connections between the external pins 2A-27 and 2D-26 and the pin 16 of the body ECU itself. That's the continuity that Toyota is having you test.

Toyota Service Information and Where To Find It | PriusChat

The schematic of the body ECU itself isn't published that I know of. You'd probably have to be their supplier, and maybe sign an NDA.

 

The "inner circuit" diagram doesn't show anything special on that path connecting 2A-27 and 2D-26 and pin 16 of the body ECU connector. Just copper.

The diagram, of course, is not showing any of the ECU itself. This path is part of the junction block that the ECU attaches to.

It might be unclear just what "board" you have swapped. Swapping the body ECU would not be expected to correct a weird reading on this test.

Alldata seems to be changing the names of some things, which probably doesn't help make anything clear. "Gateway ECU", to my knowledge, isn't a thing in a gen 3 Prius (gen 1 and gen 2 had one). The connection being tested here is between the body ECU's pin 16 and external pins 2A-27 and 2D-26 of the instrument panel junction block. From Those external pins it runs eventually to the driver's door master switch and to the window regulators in the other doors (and to the sliding roof control ECU, in cars with that).

 

I'll clarify back atcha. Alldata has screwed up some names compared to the Toyota manuals. The snapped-on pancake is the Body ECU, and the thing it is snapped onto is the Instrument Panel Junction Block. There is no "gateway ECU." (If you were working on a gen 1 or gen 2 Prius, there would be one.)

This is kind of frustrating, because Alldata is mentioned on our wiki page as one of the alternative sources for repair information, but that kind of implies they'll be giving equivalent service information and not getting the names of things wrong. Phooey.

Assuming you have a low reading on 2A-27 to ground when the ECU is unsnapped from the junction block, something in the junction block is conducting between that circuit and ground. Could some cola have been spilled in the block, or something like that?

 

Start with a better description of the problem.

1. Do all windows fail to function?

2. If just one is broken, which one?

3. If it is not the drivers window, is the failure at the door and at the master drivers control?

 

A quick and easy test with Techstream or another bi-directional scanner is to command each from the scanner. Then you know the body ecu is good and likely some parts of the Lin bus line are good.

Of course the same Lin bus line goes to all doors and there are two leading to the body ecu pin 16.

I would certainly verify the master switch pin 17 pink has continuity to the body ecu pin 16.

 

Yes, assuming you made the test described in the manual, 2A-27 to body ground with the junction block unplugged from the wire harnesses, and the Body ECU unplugged from the junction block, then your leaky ohms reading has isolated a problem to the junction block itself.

One unwelcome effect of Alldata messing the names up might be some mystery about how many computers are in the picture. The Body ECU (the pancake that unsnaps from the junction block) really is an ECU, the brains of the operation. Unplug that from the junction block, and what's left is not a computer or an ECU at all. There's nothing else in the Instrument Panel Junction Block any fancier than some fuses, some relays (occasionally with a snubber resistor across the coil), and circuit junctions. A lot of junctions. That's it.

 

No comm to the body ecu?

 

You're looking for the "instrument panel junction block inner circuit" diagram, which is in section F of the Electrical Wiring Diagram ... and continues over five pages, but everything there is to know about LIN2 is on the first page, and pretty boring ... nothing that hasn't already been said:

 

What is this gateway of which you speak?

I had said a gen 3 hasn't got a gateway ECU the way gen 1 and gen 2 had. I might not be strictly right about it having nothing called 'gateway', because some images of Techstream's System Select show two things called PM1 Gateway and PM2 Gateway ... but still, these seem to be deep mysteries of the way the Power Management Control ECU is built, and nothing to do with the Body ECU or (probably) with your issue.

 

Toyota Service Information and Where To Find It | PriusChat

 

I expect you have checked the fuses related to the junction block and ecu?


Can Techstream Read Power Window or Main Body Status and Control?

You can’t communicate to the main body ecu or the individual power windows?

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Here are some screenshots:


All devices above are communicating except for those with an * which don’t exist.



Passenger power window data list



Only one active test



Main Body Data List and Active Tests. Door lock is an easy test to verify.

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With no apparently window control from Techstream or from the driver door, I would consider isolating the Lin bus by unplugging one door at a time and retest. Both rear and the passenger door’s lin bus connects to the window regulator assembly, not their switch assembly. All four doors end up on pin 16 of the main body ecu so they are all connected.

Post 15. As stated previously the schematic of the body ecu is not available to anyone. So all we know is the door Lin bus goes to the body ecu.

The relays in the junction block are primarily driven by outputs of the main body ecu.

 

... and if the OP has measured a < 10 kΩ resistance to ground on that path inside the junction block, with the Body ECU removed and connectors 2A and 2D unplugged, then there really is something conducting to ground on that trivial path connecting those three junction-block pins, as seen on the right of the diagram in post #15.