MPG display not getting information

The display you're talking about is called the MFD (multifunction display) and it has a test mode. With the car parked and the parking brake on, turn the key ON, then press the DISPLAY button. A big rectangle outlines most of the screen. Touch the top left (TL) and bottom left (BL) corners of that rectangle 3 times each (6 total): TL BL TL BL TL BL.

That should bring up the service check screen, showing at least the Fr-DISPLAY, G/W-ECU, Panel-ECU, and Audio-H/U (maybe more entries if you have CD, Nav, etc.). Ideally they all show OK. I'm guessing one of yours won't. Maybe the lightning zapped your gateway ECU?

Sometimes it's worth doing a code clear (you have to hold the button 3 seconds) and then hitting Recheck, to make sure you're seeing current codes.

Note: this is not a secret built-in diagnostic system for the whole car, just only for the MFD/audio/nav stuff, but for this situation it's just what's called for.

-Chap

 

Lives somewhere behind the center finish panel. 89111-47010.

I suppose it makes sense to check for something simple like unplugging and reseating the connectors, before going straight to replacement. I think this is the first thread I've ever seen where it might have failed. It seems to mostly sit there and do what it does....

This old post has a .pdf with finish panel removal steps.

-Chap

 

The battery is just as disconnected no matter which terminal you undo, but in cars where the "-" terminal is grounded to the metal car body, it has always been a safety habit to undo that one first. The reason is that if you're working on that terminal with a bare metal wrench and you slip and the tool also touches a metal car part, nothing will happen (because you're working on the terminal that's already connected to the metal car body anyway). If you happened to start with the other terminal and your wrench slipped and bridged it to the body, you'd get fireworks. That's also why, if you look at your battery terminals, the one whose wire goes right to a screw on the car body is kind of bare and unprotected, but the other terminal has a big red plastic cover over it, to prevent accidental contact with random tools or metal objects that might also touch the car body.

Now, that safety habit developed back in the day when the only way to disconnect a battery was usually to take a wrench to loosen one of the terminal clamps and pull it off. Your car isn't built that way. The big red plastic module attached to the positive terminal has two cables that just plug into it (a fat one and a skinny one) using two typical squeeze-to-unplug plastic connectors. As long as you see nothing aftermarket that's been piggybacked onto the battery clamps themselves, you can disconnect your battery very simply by squeezing and unplugging those two plugs. No clamps and wrenches to deal with, as safe as unplugging something in your home. The plugs are plastic insulated and there's nothing to accidentally short to the body. If you unplug that way, it happens you are disconnecting the positive side instead of the grounded side, but if you have followed the reasons behind the old habit, you'll see why that's just fine as long as all you want to do is have the car's power be off.

Naturally, if you're ever going to take the battery physically out, you do have to undo the clamps with a wrench, and in that case for all those old reasons you do still want to undo the grounded side first.

-Chap

 

Without the battery power, a bunch of miscellaneous things get forgotten ... your radio stations ... the time on the clock ... possibly something about the auto raise/lower calibration of the driver's window, though I've never noticed a problem ... etc. If the reason you're disconnecting the battery is that you need to replace it, you can use a "memory saver" and avoid having to reset those things.

On the other hand, if the reason you're disconnecting the battery is that you want the power off while you take things apart, having a "memory saver" plugged in pretty much directly defeats that purpose.

Anyway, i think the typical "saver" gadgets are made to plug into the lighter socket, and that's built into the first panel you're going to remove on the way to getting the cluster finish panel off. Then among the next things you'll probably unplug are the radio and the clock, so you'll lose the time and your stations anyway.

-Chap

 

Those are for people who really don't want to lose radio presets or adjust their clock. Or they just like buying car gadgets.

There is no reason to use one with the Prius. I would avoid them in fact, since the car reacts so poorly to a weak full size 12v battery. Can't imagine the electronics can do much running on AAAs.

Your fuel gauge will read empty for a little while after you reconnect the 12v, but as long as you know it isn't really empty that's fine.

 

Say one follows the old way and disconnects the negative cable where it screws into the trunk floor. AND as one is later reconnecting it, there are little sparks flying from the screw as it makes contact with the trunk floor? Is that an indication that there is/are a short(s) in one of the always on circuits (ie immoblizer-alarm system)?
Ed

 

Don't worry about it. There are significant, large caps on the 12V circuit.

Bob Wilson

 

As Bob said, there are capacitors in a lot of the 12 volt loads, so it's sort of expected for those initial currents to flow.

On the other hand, in those few seconds while you're fiddling with the screw and the little sparks are flying, there are seven computers in the car that are trying to boot up at the very moment you're feeding them noisy, interrupted power. I can't say for sure yet, but this is one of my leading suspects for the non-mechanical "startless start syndrome" that many posters have seen our cars get into. My car has had SSS exactly once so far, and it cleared up when I just re-power-cycled everything by cleanly unplugging the cables at the battery terminal and just cleanly clicking them back in.

-Chap

 

Now you're asking the right kind of questions. Usually if I see a test result saying something like "MFD can't communicate with GW" I figure the problem certainly could be the GW, but it could also be ... power to the GW, oxidized connector on the gateway (often fixed just by removing and reseating the connectors), mouse-gnawed wiring, or something wrong in the MFD.... There's a bit less suspicion of the MFD just because it is working well enough to tell you it can't communicate with the GW, but if there was a lightning surge on the communication link, for example, it could have damaged the driver circuits in the GW ECU or the ones in the MFD that connect to that link.

Your basic questions like what fuse the GW ECU is on (and where the wiring is routed, and so on) will all be answered in the wiring diagram manual. $15 for a couple days access at techinfo.toyota.com if you don't have it already. It looks like the GW ECU is north of $300 from Toyota but more like $40 used online - if you can get it that cheaply, it might not be unreasonable to just try it and see if it solves the problem, and do more diagnosis if it doesn't. Well, or maybe try obvious things like fuses and reseating connectors first, then try the GW ECU and see what happens. You might want to just have one on hand anyway, so if you need one you don't end up having to repeat the labor of getting behind the finish panel.

-Chap

 

That's weird, it worked fine for me just Wednesday. Now it doesn't. I think it was uploaded as an attachment so it should be hosted on priuschat, not a dead link to somewhere else. Maybe it should be reported that it's stopped working.

-Chap

 

According to the repair manual, a communication failure with the gateway ECU should trigger DTC 93.

Inspection procedure is to check the open door warning light.

I'm not familiar with the ECU, just reading what is says.