The car was misfiring upon starting. So I decided to change the spark plug in my 2012 Gen 3 Prius. It has 250,000 miles and the spark plugs had not been changed. I got everything apart and put the new plugs in. I got side tracked and went back and started the car. In ran incredibly bad. After searching for potential problems it occurred to me that I had not put the coils back onto all but one of the spark plugs. After doing so, the car ran quite smoothly. I have not had any further problems. I ran a health check on the car and it has several codes relating to this situation. P0351 P0352 P0353 Ignition Coil A, B C. Primary/Secondary Circuit Permanent and P3190 Poor Engine Power. I can not clear the codes. With the knowledge that the car is running fine, is there any repair or procedure that is necessary? I have included a picture of the spark plugs that may add incite to the situation. Thanks so much … Vegg
You clear those codes now because you know that's not happening and then you drive the car and see if you get codes again probably not You created the codes now you've uncreated them but do clear them out and start afresh
Permanent codes aren't clearable. The permanent P0351 will go away the next time the power is turned on (IG) after three consecutive drive cycles have run the P0351 monitor and judged the operation to be normal. If you're in a hurry, you can use the confirmation driving pattern in the repair manual. For this code, it's not much more than idling the engine for ten seconds in maintenance mode. As with any confirmation pattern, that means starting by doing a code clear. That won't clear the permanent code, of course (see: permanent codes aren't clearable), but it will reset all monitor results to incomplete, so the ECM will run them at the first opportunity. Then you give it the opportunity (for this code, just ten seconds of maintenance-mode idling). Then finish up with a universal trip. This stuff is described in the repair manual under Engine and Hybrid System ➡ Engine Control ➡ SFI System ➡ DTC Check / Clear. Toyota Service Information and Where To Find It | PriusChat Because any time you do a code clear, all of the emission monitors get reset to incomplete, the various different monitors will then be completing themselves in your later driving. This one has a pretty simple confirmation pattern. Some of the others have more complicated patterns that will take longer to hit as you normally drive, so it might be a while before they all show ready again. If there is emission testing where you are, you'll have to wait for all the monitors to be ready before an inspection. Sometimes (say, if you have an inspection coming up), that could be a good reason to skip the code clear, so that you don't reset all the other monitors, and instead just wait for this one to see the P0351 fixed in three consecutive drives and go away on its own.
