I have an error code po354 which cylinder is that

The ignition coil on the number five cylinder may have a bad connection or bad power or ground control causing a misfire . Sometimes the coil itself may be bad .

PO354 Ignition Coil D
Primary / Secondary Circuit Malfunction

TYPE: OBD PO354

Do you know for a fact cylinders one two and four are firing ?
The codes are for circuit problems with the coils on those cylinders. The coils get power from the PCM power relay and the engine computer grounds each coil to fire the spark plug. The codes mean the coils are not firing, and since you replaced the coils there may be too much resistance in the circuits coming from the computer.

Possible Bad COP Ignition Coils on #4 & #6 cylinder

Forget the 300 & 316 of no use to you

PO 304 is the same as PO354 or letter D
PO 306 is the same as PO356 or letter F

If the codes are the actual bad coils -you won't have to pull
the upper intake off

PO354---- Ignitioncoil #4 primary circuit fault

All parts are expensive for the lexus, try www.AutoMD.com for labor and parts for your area

PO122--ETC Throttle Position (TP1) sensor Low Input

PO223--Throttle Position (TP2) High Input

PO354---Ignition Coil D --On an LS, that is not
a used code,another engine it would be cylinder #4

What I believe you have,having diagnostic experience
and also owning a 2004 LS,is a Bad COP Ignition Coil
on cylinder #4 that is bad enough to spike the PCM
& come back on the TPS Sensor

You ignore the codes and buy 1 new coil for $59.00
and put it in #4

If that doesn't help,remove the new coil and walk it to
another cylinder and drive a couple days,continuing
to move the new coil.

If you had some very expensive diagnostic equip
you could go with a different approach

The last thing you EVER want to do, is go to
a dealer,you may leave there the same as you were,
and a bill for a grand per visit.

IF you have a V6 and I hope you do not,
then if you get involved with cyl #1 thru 3 where
you have to remove the upper intake,do the spark
plugs on that side and all new coils while in there.
Save those coils for your future diagnostics

These coils fail at a rate of 1 or 2 a year on all fords

it's for a bad coil pack or COP, coil on plug

I just worked on 98 expedition 5.4l had code PO354. This code refer to an open primary coil winding, open wire, or bad PCM.
Check primary winding with ohm meter should be from 0.5 to 1.5 ohms and about 2.5 ohms with a hot engine. check wiring with a noid light, run the engine and shake the harness if light goes out repair harness you should have battery voltage with key on the computer controls the ground side.

if you are standing in front of the vehicle looking on the left side cyl #4 is the second one back from the front. Follow the wires to see where coil is. Or it may have coil on plug.