Just a heads up, and a good one. If your 99-01 ES300 throws this code, be aware that the coil pack is relatively easy to change; almost as easy as the three front coil packs. It is not necessary to remove any of the intake parts or hoses at all. There is enough room under the intake plenum to disconnect the electrical connector and pull the coil pack up and out.

I was initially dreading this job, as I have replaced the 301 and 303 coil packs and it is not fun at all. I was happily surprised the 305 was straightforward. On all my P030X codes, the solution has always been a coil pack and never a fuel injector.

One hint, I have always use the OEM Denso coil packs. I have now replaced 5 of the 6, the latest at 217000 miles. They are around $50 on Amazon and well worth it.

Happy wrenching!