Elusive P035* error code

[makaplan]

Hi all

I am stumped by this one on my wife's Corolla.

Will I have to replace all the coil packs, or is there something else I should try first?

The error first came up in 2017 (after a spark plug change by the Toyota dealership), then disappeared for 4 years and now it is coming up again.

Recent sequence of events:

-It started having intermittent misfire, rough idle, low power etc. which would clear for a few days and then return.

-The check engine light came up and it was a P0352 Ignition coil B primary/secondary.

-To determine if it is a harness fault, coil pack or sparkplug, I moved along all the coil packs by one position and all the sparkplugs by two positions.

-The next time the fault came up, it was P0353 Ignition coil C primary/secondary. Since the fault had moved together with the coil pack, I bought a genuine new Toyota coil pack and replaced it. I naively thought that would be the end of it😅

-However, the fault came back and this time it was on P0351 Ignition coil A primary/secondary. Now I am really confused because neither the coil nor the sparkplug on Cylinder 1 had come from Cylinder 2 where the fault came up originally.

Some additional information:

The fault only ever comes up on one coil pack/cylinder until I move the parts, so I don't think all the coils are packing up.

The sparkplugs look fairly good and were replaced 50 000 km ago, so I don't think it is them.

Please help! Any advice will be appreciated!

 

[Red_Corolla]

The misfire counters are not always 100% reliable at identifying the correct cylinder. I would start by checking the plugs and making sure they are the exact right part for the engine, not getting fouled etc.

After that, the only reliable way to pin the problem down is to go to a proper automotive diagnostic technician with an oscilloscope and the knowledge of how to use it. They will be able to find the one bad cylinder or tell you if the coils are all breaking down. Never change parts just because of a fault code. The code is only a clue.

[makaplan]

Thanks for the advice. The plugs are definitely correct and in good condition, so I will have to get a technician to take a look. 

 

Regarding buying parts based on a fault code...yeah, I have now learnt that the hard way!

[Red_Corolla]

I made a mistake when I replied before because I thought you were talking about a misfire code (P030*)

I think P035 codes are specific to the coil electrical circuit. It's probably telling you that there is no feedback received when it tries to charge that coil. Toyota usually use a 4 wire system:

+12V

0V (Earth)

Ignition trigger (IGT)

Ignition feedback (IGF)

 

Only IGT has 4 separate wires back to the ECU. The rest of them each share one wire. When the ECU turns on a coil using the IGT wire, it expects to receive a feedback signal on the IGF wire at the same time. This confirms that the coil is charging (but does not guarantee that it produces a spark).

This is why you need an oscilloscope to test the system properly. That single IGF wire is carrying the signal from all 4 coils and you need to see if it's coming on at the same interval every time, because a big gap means that one of them has not worked, but we're only looking at milliseconds between each event.

Unfortunately, I think the code might be telling you the truth. Does the car misfire from cold? A coil will often break down with heat when it's beginning to fail.

 

 

 

 

 

 

[makaplan]

It is definitely the coil code.

Thanks, this detail is very useful! 

The fault is intermittent and quite infrequent. Will it only show up on the oscilloscope while the misfire is happening?

If that is the case, then it is going to be unlikely that it will happen while I am at the technician. It typically only happens every few days for a short period and the returns to normal.

We haven't noticed any connection to engine temperature. It seems to happen randomly when the engine is hot or cold.

One thing we have noticed is that once the fault has come up, it tends to keep misfiring for that trip. Maybe that could be due to temperature.

We will pay attention to that and post new findings if we see a pattern.

 

Cheers!

 

[Red_Corolla]

Unfortunately, yes, you have to catch it while you have the fault to prove it through testing. But the reason I gave the explanation was to show that you can probably trust that code if you just confirm that the wiring connector is good by swapping the bad coil with the new one (the same thing that you did before).

It is reasonable to think that when one of the original coils has failed, others could follow. The only other tip I could give is to inspect the coils carefully inside the rubber boots and look for carbon tracks. That would give you a misfire but I don't think it would be responsible for that code.