You can tell from the name, I'm sure, but this code indicates that either random cylinders are misfiring or multiple ones are. Luckily this isn't very hard to diagnose.
You're gonna have to have a look at your spark plug system. A lot of times, the problem comes from just bad spark plugs. Mine was created by a few factors and here they are.
For one, the negative battery terminal had screws shoved inside it to hold it onto the battery. I took them out and fixed the terminal and this helped already. Especially in a Lexus, a bad battery or connection alone can cause a random misfire. With a new coil pack and that, the car went from bucking (loosing 2-3 cylinders and bucking back and forth) to simply shaking at stops. Why does a crappy connection matter if it doesn't seem to affect anything else? Because while you might not feel it, for milliseconds at a time your car misses some of the electricity it needs and that's critical.
Spark plug wires.
Then I went on to change the spark plugs and this is where I found the main problem. Changing the plugs made the car completely drivable with a slight misfire because of what I found. One of the spark plug wires is ripped. It's literally making some contact when I shove it into the plastic protector that connects to the spark plug. So with good spark plugs and everything, now the car still has the problem until I change that one wire.
New coil pack. Need to clean that engine bay...
Because the wire does have some contact, like I said, the car drives on all cylinders 90% of the time. I'm waiting for an LS400 to show up at the junkyard to change out the wire.
I could have sworn I saved the wires from the '95 I sold but I can't find them! Keep your extra parts, people.
As you know by now, this code comes up when one or more cylinders (spark plugs, really) stop firing randomly. Because this isn't something like a 'misfire in cylinder 4,' it tells you that there is a problem with electricity being delivered to the plugs. Or if it is, they aren't firing correctly.
It could be the distributor or distributor rotors (the latter on the LS400 but this problem is the same on all cars) as well.
In order, start by checking your battery and the connection. Make sure your battery is actually good by testing it. Next, replace your spark plugs and/or coil pack - at this point it could be either one or both. The coil pack will help anyway and you need to do them both. The order is up to you. If you still have a problem, you might need to replace your wires and finally, if that doesn't do it, your distributor or distributor rotor. You may want to start with just the distributor cap(s) first. There is a different cause of this problem that I will discuss below and that is a bad fuel filter. If you suspect that you have a bad fuel filter or pump, I would probably try changing that out after doing the spark plugs.
One stupid thing that can cause this problem too is simply tainted fuel. The LS400 ONLY likes 93 octane gas and it can't have more than 10% ethanol and I believe 5% methanol so be careful.
Wiring diagram thanks to the forum on Club Lexus.
Two more parts that can cause this problem aswell is the ignition coil (looks like the coil pack on the LS400) or, just on the LS400, the Coolant Temp Sensor if you have tried everything.
There is one more potential cause but I would think it would be accompanied by other symptoms like the car taking a long time to start (crank). That would be a bad fuel filter. If it's partially clogged, it is possible that random cylinders don't get enough fuel at random times, of course causing the same problem. A bad fuel pump could also be the culprit but I would try changing the filter first if you suspect it's a fuel issue.
If I missed a potential cause, please let me know. If you have a misfire, I know it sucks, and I hope this helps you get your car running good. Good luck and share with your friends if you enjoy these articles.
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