cwmoody

I have a 2006 Lexus LX470 with 217,000 miles. Last week my wife complained that when she was stopping and going in car pool that the transmission seemed to engage with a knock sound. Almost like there was slack in the drive train or that something rocks back when you take off. I have noticed this before when I have driven it, but it seems to have gotten worse. It shifts perfectly fine through the gears though. I explained the problem to the local transmission shop and they said it sounded like the chain in the transmission box had developed slack over time. They said they have seen that occur in a handful of high mileage LXs. I took it in for them to check out. They drove it and said they felt what I described, but said it was not the transmission box chain. And said the transmission checked out fine. They said the only error codes were all ABS Codes and nothing related to transmission. The codes were C1223 Malfunction in Antilock Brake System, C1241 Low Battery Voltage, C1290 Malfunction Steering Sensor, and "C1340 OPN CKT IN CTR DIFF LCK SIGNAL." The transmission shop suspected that the vehicle experienced low battery voltage which in turn caused some computer settings to get reset and resulted in the additional error codes. And they thought this very well could be causing the knock when taking off/slack feeling when stop and go driving in the 5 to 10 mph range. This seemed plausible to me since my alternator went bad back in June. And the ABS code makes sense since my wife also complained about the brakes squealing loudly, but only in carpool. They recommended a local shop that specializes in Lexus and said the codes needed to be cleared out with some sort of "flash." I called the shop and they said to unhook the negative battery cable for about a minute and that would clear the codes, and if I experienced any issues after that to bring it in. I unhooked the battery cable as instructed this morning. The vehicle started fine after that, but immediately died. It started back fine, but air was blowing hot air on her way to school. Since turning the vehicle off at school and restarting it, it has been running fine and air cooling fine.

Does any of this make sense? Any information or recommendations are greatly appreciated. I am baffled by all this.

hankinid

It will continue to make no sense until it's hooked up to TIS at the Lexus specialist shop.

Report back and I hope whatever it is is cheap to fix.