RX400h datalink/canbus errors: hybrid system intermittent

[not impressed]

I have 2006 RX400h that was my father's car. So far, it's been a real disappointment. There is something wrong with the wiring/data connections that doesn't allow the hybrid system to work properly. The Battery in the info display is only green some of the time, purple the rest, and the aux Battery status is gray. Scanning it with a OBD scanner will brick the car. The VSC/AWD/Hybrid system will all flash errors and the power steering will also be inoperable. Dis/reconnecting the aux Battery will restore it. 

The local dealer recommended replacing the ECU and hybrid relay under the rear seat and those were done by my independent shop (no way I was paying dealer rates). No change so their diagnostic was useless. They were only willing to throw parts (and money) at it vs looking at any diags from their better scanner. I assume their scanner would allow them to see why my simple OBD scanner would brick the car. There was water intrusion from blocked sunroof vents, that has now been cleared and the interior dried out. My mechanic didn't see water during his work. The only mod I know of is a radar detector that seems to be wired in behind the dash: the wire is routed behind an interior trim panel but I have no idea where it was cut into the harness or fuse panel. The OBD fuse was blown when I got the car which tells me how much previous mechanics used that diagnostic tool. 

I think I am giving up on this thing. For a "free" car it is turning out be the most expensive and least reliable I have owned in my life. Anyone else seen any of this? 

[katabrontes]

This is really bad news.  I think you would better to cut your losses and dump it.

[not impressed]

I think that's the course I am on. Disappointing for sure. It drives well and now that I have replaced the aux Battery, it starts reliably…unless I do an OBD scan. The fact a simple dis/reconnect of the Battery should be a clue as to where the problem is. I keep hoping there is something that's been overlooked, some component that will resolve all this. But without a motivated dealer, there's not much I can do. They charged me USD1600 to dry it out and do their weak diagnosis so I won't be seeing them again. Toyota dealers won't touch it though it's essentially a Highlander underneath. 

Time to take some pictures and clean it up, I guess. 

[Bluemarlin]

Sorry to hear of your troubles, but I'm struggling to grasp what the current problem is.

You say that the car's running fine now, so what's the issue?

[Herbie]

11 hours ago, not impressed said:

It drives well and now that I have replaced the aux battery, it starts reliably…unless I do an ODB scan.

So...if it drives well and starts reliably, that sounds like a good car to me.

If you get problems when trying to do an OBD scan then your OBD reader could be faulty. If you have a laptop then buy one of these miniVCI cables from eBay They usually come with a pirated copy of Techstream, which is the exact very same diagnostic software used by Toy/Lex techs in the dealership workshops, so you won't get a better diagnostic tool than this, especially as it shows sub-codes as well. For instance, P0AA6 covers six different areas with only the sub-codes to differentiate between them.

Of course, we can't be seen to condone software piracy (that's a matter for your own conscience) so the legit way would be to download Techstream from here and then pay for a block of time to use it (€5/day or €10/week etc). Whichever way you decide to do it you'll need that VCI cable anyway.

If all else fails, I strongly suggest taking it to a specialist auto electrician. It's a skill and a trade in its own right and you wouldn't employ a painter to install a whole new central heating system in your house, or a carpenter to do some plumbing work, so why expect a general mechanic to be able to sort out auto electrical problems? I don't think Lexus dealerships will employ their own auto electricians because I just can't see them having enough work in that area to keep someone in a full-time job.

[Illogan]

Excellent advice Herbie!

[Greisingel]

Get a reliable Techstream here. Bit of a shenanigans but you get a stable platform. You should be able to read the exact problems from the ECU.

Note: Herbie is right re conscience. But you can at least get Windows XP (we don't cry for Microsoft).

You've got to read the ECU somehow before going down replace route.

Get all your fuses triple checked. Make sure you don't have any water ingress – a real gremlin with the 400s. And Hybrid Battery filters must be kept clean.

[not impressed]

And I'm out…the catalytic converter was cut out last week and I had already decided to get it appraised. that took the appraised value from $4k to $2k. Looking at an $800 valve cover gasket replacement and tires plus a new cat? No thanks. 

As for the issues,the hybrid system doesn't work reliably (or Lexus's own info screen is dodgy), the Battery never gets fully charged, the gas mileage is not what it should be. The dealer wanted to throw parts/money at it…I replaced the ECU and the hybrid relay. There is a hybrid Battery control unit I didn't see on the diagnostic and that they didn't call out at first. That was probably where to start.

The OBD scanner software might be an issue but it seems like it shouldn't brick the car. there is definitely something up with the comms between components but it's no longer my problem. I suspect it was tampered with when the radar detector was hard wired in or something else over the years. The OBD port fuse was blown when I got it so that tells me something was done somewhere. 

So the poisoned chalice can pass to someone else. 

 

[Bluemarlin]

Sounds like you inherited a car with a few problems, possibly due to a previous electrical installation, and a dealer keen to just take your money.

For the record, the hybrid Battery rarely (if ever) shows fully charged on the info screen.  That's not a fault, it's just how it is. During driving the Battery gets charged, but also used, and the computer keeps it within the correct parameters. If the car drives ok and isn't throwing up any hybrid system faults, then I'd guess the system was working ok.

[Greisingel]

Hybrid Battery monitor goes green when it hits 80% safety max.

Yes, I had my cat cut out. Straight piped it and just hope the VOSA what shall we do now committee idiots don't enforce a hybrid emissions test.

My 2005 RX 122000 miles is pretty reliable and hassle free. Replaced the rad after usual plastic neck explosion.

Sealed the car after dodgy seams turned it into an indoor swimming pool – POAA6ed the hybrid Battery. That was some drying out.

Value...about £2K tops. Paid 4