Code U0155 Lost Communication with Instrument Panel Control Module

[BigSwede]

My GX doesn't see much action in the winter, trying to keep it out of the road salt. I went on a long vacation in December which was followed by very cold temps upon returning. Then I realized I hadn't put a tender on the battery, so I put a smart charger on it and when it said full I went to start it. Battery was dead, so I tried to start it with a lithium jump starter. It ran for less than a second then shut down, which happens every time I start it after disconnecting or replacing the battery, so I didn't think anything of it. Subsequent attempts got nothing but a click. I got a multi meter and got a whopping 4.5 volts on the battery, so I figured it needed replacement either way.

Today I installed the new battery and the GX won't start. All the lights and instrument panel lights and activity look normal, with the exception of the check engine light. Nothing else but a clinch when I press the start button. I found my code reader and got a U0155 code Lost Communication with Instrument Panel Control (IPC) Module.

I'm thinking fuse, but in an inspection of the engine compartment and kick panel fuse panel covers, none of the fuses are labeled IPC. There is one called PANEL but it is fine, which I expected because the instruments all light up normally when I try to start the vehicle.

I'll pull every fuse if I have to, but maybe someone has been through this before and can narrow my search? Internet guidance is too generic to help much.

2018 GX Premium 118k miles,

 

[iwashmycar]

Now that you are not tying to start it with 4.5V I’d try disconnecting the battery a while, reconnecting, and seeing if it persists.

 

[BigSwede]

Now that you are not tying to start it with 4.5V I’d try disconnecting the battery a while, reconnecting, and seeing if it persists.

Yeah, it was disconnected for about a week before I installed the new battery.

 

[Rednexus]

I'd suggest getting a copy of the FSM for your GX. It should have troubleshooting recommendations for this specific code. I think a few folks have posted the FSM on here. The FSM is quite handy for weird vehicle-specific codes like that.

 

[BigSwede]

I'd suggest getting a copy of the FSM for your GX. It should have troubleshooting recommendations for this specific code. I think a few folks have posted the FSM on here. The FSM is quite handy for weird vehicle-specific codes like that.

Okay, found the FSM. What a byzantine labyrinth that thing is.

Anyway, if I read this right I may be able to just clear codes now that I have adequate battery voltage. Worth a try, anyway. Otherwise I'll be pulling fuses.

 

[iwashmycar]

Okay, found the FSM. What a byzantine labyrinth that thing is.

Anyway, if I read this right I may be able to just clear codes now that I have adequate battery voltage. Worth a try, anyway. Otherwise I'll be pulling fuses.

This is what I had meant - now that you have a good batt, disconnect it to clear the codes (or I suppose a scanner could). If it recognizes the connection once reconnected then youll be good to go

 

[Rednexus]

Okay, found the FSM. What a byzantine labyrinth that thing is.

Anyway, if I read this right I may be able to just clear codes now that I have adequate battery voltage. Worth a try, anyway. Otherwise I'll be pulling fuses.

Yes, it's a monster. The GX470 FSM is a 3,000+ page PDF. I find the 460 FSM harder to navigate as it's not a "book" but a file structure you have to navigate.

 

[r2m]

Yes, it's a monster. The GX470 FSM is a 3,000+ page PDF. I find the 460 FSM harder to navigate as it's not a "book" but a file structure you have to navigate.

And it doesn't help that you have to be online with a website to to use it, even though all the PDF's are downloaded on your hard drive..

 

[BigSwede]

Bit of an update. Clearing codes didn't work. I should clear codes and also disconnect the battery for a bit, as someone suggested. Easy enough to try.

I checked all the blade fuses in the engine compartment, and any that seemed related to ignition in the passenger compartment fuse box. Didn't find anything other than a hatred for tiny blade fuses. I guess I should look at the rest as I have seen odd combinations of functions beyond what the label says, on other vehicles. I had one that had the instrument panel on the fuse labeled "taillight". But I'm not all that optimistic I will find a problem. The bigger fuses (like 50 amps or more) in the engine compartment fuse panel were harder to read, for me anyway. They all look a bit melted which I assume is normal.

If none of this turns up a problem, I may have to have it towed to a shop. Unless someone has another suggestion?

 

[Rednexus]

I suspect that you have a CANBUS module that is fried or you have a loose connection somewhere. I'm presuming the FSM will require lots of multimeter testing and at least partial dash disassembly to fix the problem.

If you are comfortable with troubleshooting electrical systems, I'd buy the requisite diagnostics tools and move forward. If that is not your cup of tea, I'd get it towed to a Lexus dealer (unless you have a capable independent shop around who can handle CANBUS diagnostics and has access to the full GX460 FSM). It might be something they can fix in an hour by plugging something back in, or it might cost thousands of dollars.

 

[BigSwede]

I suspect that you have a CANBUS module that is fried or you have a loose connection somewhere. I'm presuming the FSM will require lots of multimeter testing and at least partial dash disassembly to fix the problem.

If you are comfortable with troubleshooting electrical systems, I'd buy the requisite diagnostics tools and move forward. If that is not your cup of tea, I'd get it towed to a Lexus dealer (unless you have a capable independent shop around who can handle CANBUS diagnostics and has access to the full GX460 FSM). It might be something they can fix in an hour by plugging something back in, or it might cost thousands of dollars.

Yeah. Thanks for the input. The fact that it ran very briefly when I jump started it suggests something popped. I was hoping it was a simple fuse, but...

 

[BigSwede]

Well. So this all turned out to be much ado about nothing. How embarrassing.

Turns out, when I swapped in the new battery, I neglected to reconnect one of the two positive cables to the battery. Because my GX is lifted, I did all the work from the side of the engine compartment and didn't see it dangling down by the engine. So when I swapped out the dead battery and messed up the install, I exchanged one no-start condition for another, which was a major red herring.

The GX starts and runs fine now.