Well it happened last night. Out of nowhere, Check VSC/check engine, skid light, and red triangle came on in the cluster. Car was running fine, tried tightening the gas cap (filled it up shortly after) with no luck. Lights were still on this morning, car was running fine up until I was stopped at a light, at which point I got a momentary (literally 2 seconds) stumble and the car continued to run fine. Had the light run at AutoZone, came back with a P0354 ignition coil D.

Now, when the check engine comes on, it'll disable the VSC and trac systems until it's resolved, hence those lights showing up as well. Good try Lexus making it look much scarier than it is to get people back to the dealer.

P0354 for coil D is coil #4, which is the front and center coil, primary/secondary circuit. Basically, it's saying 'there's SOMETHING wrong with the coil...' Again, how helpful. Here's a bit more info for anyone reading this that has had the same issue. Primary circuit is the external connector on the coil that connects to the harness, with the secondary circuit being the actual end of coil that connects to the spark plug.

So, troubleshooting will begin by pulling the engine cover, disconnecting and removing the coil. My suspicion is that the dealership I bought the car from blasted the plastic covers with a pressure washer during detailing and i've either got dirt/dust/corrosion in the primary connector to the harness, or the spring that runs down and carries the current to the spark plug is broken/shorting out. I'll start by cleaning it, and seeing if the codes come back. If they do, I'll swap coils from front center to front left, clear it and see if it follows the coil. That will tell me if it's the coil or something in the wiring.

Autozone puts the coil at $113, if I remember correctly Toyota has them for $99 and Lexus is around that as well. So worst case if I do have to replace it, it won't break the bank.

 

Do check for water/cleaning solution and oil in the spark plug tube/s during your troubleshooting, but don't be surprised if the coil is failing/duff. It's not that uncommon.

 

Pulled the coil, connector looked fine, no debris in the plug shaft, no debris in the bottom of the coil boot, so I took a wire brush to the connector pins and into the boot, checked for cracks/arcing marks but nothing there either. Reassembled it, cleared the codes and it ran fine all the way til it got up to temp on the highway, at which point it broke up at around 2000rpms. Stepped on the gas and gave it some load, went right back to normal. Read the code when I got home, coil D again.

Looks like a coil is in order. I may swap it with #2 just to verify it's following the coil, but given how cheap they are I may as well just buy one. I'm just thankful it's a coil on the front of the motor and not the rear bank haha

 

I experienced the same issue with my ES350, but it was coil #5. I ended up replacing all the coils (1,3,5) in the rear bank after pulling the intake manifold. The OEM part number for these coils is 90919-A2007 and costs $68/each. For some reason, these coils only last about 50,000 - 75,000 miles.

 

Certainly the smart way to do it for the rear bank since you have to rip the whole top end apart basically, but I think I'll only be replacing the one (and may not even have to pick up the tab...battling with the dealership I bought it from over unrelated issues but now I think I'l add this to the pile) since it's on the front bank. It seems as if they're exposed to quite a lot of head under there, and as we all know electronics and heat do not mix very well.

 

Quick update, I was pissed at the honda dealership that I bought the car from due to some unrelated *****ery, so I brought it back to them to have the TPMS light and CEL situation looked at. In no uncertain terms, they basically said they'd look at it for themselves and let me know. In a HUGE stroke of luck, the SA in charge of used cars there is a great friend of mine from high school. So the TPMS light and ignition coil will be fixed, and he's going to try and get one of his guys to install my 3000K fogs for me while it's on the lift. Score!

I don't think i'll get them to pay for a 2nd key but ill take that hit while they're fixing what's wrong on their dime.

 

Another update, my buddy the SA called me back. They found exactly what I did, ignition coil D and random misfires on all cylinders. so, aside from Coil D which is throwing the code, he's going to push to get all 6 plugs done also. I'm going to give the car a once over tomorrow during daylight to make sure nothing else is afoot.

 

Well, coil D replaced as well as all 6 plugs. Running right as rain now.