P0351 Toyota - first saw 354, now I'm seeing 351 and 354?

Question

So the first time my check engine light came on, I got a P0354, did a little research, and replaced all 4 spark plugs, and the 4th ignition coil from the left (guessed that this was Coil "D") . Started it up, and it sounded good, and no check engine light. This lasted 2 days of commuting (not a horrible commute). On my way to work this morning ,on the highway at cruising speed, check engine light came on again. Checked the OBD scanner tonight, and it's showing P0351 (coil A) AND P0354 (coil D) ???

Maybe the problem is independent of the coils - like wiring or ECM?
Maybe coil D isn't 4th from the left when looking down at the engine from the front of the car, and I replaced the wrong coil originally ?

Answer 1

P0351 Ignition coil A primary / Secondary circuit

P0354 Ignition coil D primary / Secondary circuit

How was the idle? How was the acceleration? P0351 and P0354 this is more of an ignition coil concern. If P0351 was the first time a CK ENG LT came on. sparkplug replacement was a good choice especially if it needed it. What P0351 refers to is cylinder 1 ignition coil, P0352 is for ignition coil number 2 cylinder, P0353 is for ignition coil number 3, and P0354 is for ignition coil number 4 cylinder, when either P0351 thru P0354 occurs it refers to 2 possible conditions, the transistor in the coil is shorting out or open. it is the ECM that uses the transistor to control timing thru an IGT circuit. Because this is a 4-cylinder engine the proper sparkplug specification has to be correct which would be a Denso part # SC20HR11

 

This is a Toyota ignition coil for cylinder number 1, When codes such as P0351 through P0354 occur it is advisable to replace the ignition coils as a set.

Here are the cylinder ignition coil locations

 

Here is another possible condition whenever P0351 or P0354 occurs It usually always happens when a tune-up is performed, what happens is the use of di-electric grease is applied, it is good to use but too much will set a P0351 thru P035X ( X - depends on how many cylinders)