Bouncy Ride (AHC), P0504, P0571, and P2447

[Dmmack]

Hey all, I have a 2010 LX 570 (my second cruiser, first was an '06 LX 470). I've had a super bouncy ride since about a few hours after buying it used. It has had the the 4Lo flashing occasionally, and my mechanic scanned to show a faulty brake switch. Now I just got the Check VSC System, check engine, and and slip indicator lights. Had my mechanic scan it, and now the P2447 code is showing in addition to P0504 & P0571.

Seems like two separate issues, but I could be wrong.

1. Bouncy Ride and sometimes flashing VSC lights when braking hard (says something about checking the AHC system too, I think). Does the AHC need new globes/accumulators? Is this the best route rather than the lengthy diagnostics and shrugged shoulders, "replace it all" suggestion from Lexus?

2. Tackle the P2447 error: replace this module? What is the best approach here?

3. Are two systems/issues related?

Thanks for all your help, and I apologize if I'm missing something already posted.

 

[lx200inAR]

I would say you have a few issues.

P2447 is the infamous SAIS failure. You can either fix it or get a bypass module.

The other two errors sound related to the brake electrical circuit, which would be unrelated to both the SAIS and AHC. Well, i guess it's possible AHC could be doing some quirky things if it's unhappy about whether it knows about the status of the brake pedal.

The SIAS failure alone can cause all those lights in the dashboard. Any emissions related failures will cause the all the 4wd stuff to light up.

I'd get the brake circuit situation worked out and go from there.

 

[Dmmack]

I would say you have a few issues.

P2447 is the infamous SAIS failure. You can either fix it or get a bypass module.

The other two errors sound related to the brake electrical circuit, which would be unrelated to both the SAIS and AHC. Well, i guess it's possible AHC could be doing some quirky things if it's unhappy about whether it knows about the status of the brake pedal.

The SIAS failure alone can cause all those lights in the dashboard. Any emissions related failures will cause the all the 4wd stuff to light up.

I'd get the brake circuit situation worked out and go from there.

Thanks so much. Is the P2447/SAIS failure an emergency, as in don't drive it at all until fixed? I've been driving on it for a few days until I could take it in for a scan. I can't tell any difference in the way it drives or functions.

Great advice on working out the brake circuit. Is the SAIS failure expensive to fix?

 

[lx200inAR]

Thanks so much. Is the P2447/SAIS failure an emergency, as in don't drive it at all until fixed? I've been driving on it for a few days until I could take it in for a scan. I can't tell any difference in the way it drives or functions.

Great advice on working out the brake circuit. Is the SAIS failure expensive to fix?

SAIS system runs for the first 20 seconds or so after a cold start (when the engine makes a loud whirring sound on cold starts, that's the SAIS system in action). After it shuts off, it's not in the equation for normal drivability. Sounds like yours failed in the way that doesn't incur limp mode. If you don't get limp mode, it's not going to hurt anything to drive it.

Cost to "fix": The bypass kits range anywhere from a full diy for under $20 to bypass (the most expensive retail bypass kit is $450) and upwards of $4k to have a dealer actually repair it for you. Probably many prices in between depending on how you go about it. A quick google of Toyota and SAIS will give you plenty of info as it's famous across all the Toyota body on frame lineup.