Check engine light has come on & getting P0351 error code

[tempestv8 Member Find all posts View Profile Close tempestv8]

Howdy group,

Trying to troubleshoot a Prado 120 V6 engine check engine light issue.

The engine seems to be idling slightly lumpy, as if as one of the 6 cylinders is not firing. Starts up fine, no issue with cranking battery but can feel a slight tremor throughout the vehicle.

The amber CEL light is on solid, as well as the two traction control lights next to this warning light.

Using a Scangauge II, I am able to clear the CEL light whilst the engine is running, but a couple of seconds later the CEL light reappears, followed by the traction control lights.

A scan of the computer with the SGII reveals only one error log in the ECU - a P0351 error code. I believe this translates to ignition coil "A", whatever that means.

Has anyone seen this problem before. I have unplugged the wiring loom that connects to cylinder 1, checked that it's clean and refitted it back snugly. I believe cylinder 1 is the first cylinder nearest to the engine air cleaner box release latches.

Any help would be greatly appreciated. It could well be a faulty ignition coil but instead of replacing parts, if there's a way of diagnosing the problem better, I'd like to find out how.

Vehicle has around 180,000 kms on it, and has never been offroaded. All highway driving. Sequential LPG fitted 4 years ago, but the lumpy idle occurs irrespective of whether running on petrol or LPG, so I am presuming that the fuelling system is OK.

[winniliss Avid PP Poster! Find all posts View Profile Close winniliss]

Did a google and come up with this P0351 Ignition Coil "A" Primary/Secondary Circuit Malfunction

[Steve M Addicted PP Member Find all posts View Profile Close Steve M]

By the sounds of it may explain the lump idle you have mentioned ??.Cheers Steve

[tempestv8 Member Find all posts View Profile Close tempestv8]

Thanks for the replies, thus far, guys.

Yes, it's a 1GR-FE Prado Grande - one of the first ones with the newer 5 speed auto.

I am thinking that if one ignition coil needs to be replaced, is it worthwhile replacing all six, or was it just unlucky?

I had a BMW 6 cylinder where one of the coils failed, and the dealer replaced just one. Then another coil went the next year and I replaced the remaining 5 of them, because I figured if two failed within a short space of time, the rest are likely to be not long lived.

But I'm not sure if this sort of thinking will hold true for the Toyota V6 motor.

[state50 Lurker Find all posts View Profile Close state50]

That fault code relates to a faulty coil more than likely. Usually a P0350 is a generic misfire and a P0351, or whatever number is on the end is related to that cylinder. Firstly, i would pull the spark plug and check for any signs of damage to the body (ceramic/porcelain) usually small cracks with tiny burn marks and check the end of the coil/lead looking for white tracking marks that look like lightning almost and a sort of white discoloration.
If you know how to test a ignition coil you could try that, but if it is intermittent then sometimes that doesn't show up when testing. I often swap one coil from another cylinder and check the fault codes again and see if it changes.
Also, don't count out the possibility of a injector being dirty/blocked that could be causing a lean misfire and a signal feedback to the coil which then logs the fault code.

[state50 Lurker Find all posts View Profile Close state50]

And no, I would save your coin ad only replace the one that is faulty.

[tempestv8 Member Find all posts View Profile Close tempestv8]

Just to update you guys on this thread, I devised a plan on how to isolate the faulty ignition coil. However, to my chagrin, Toyota engineers have created an incredibly well engineered engine with this 1GR-FE V6 motor.

My plan was to pull off one of the lead off one ignition coil, start the engine, and then see just how roughly the engine runs.

I was going to systematically try disconnecting one ignition lead at a time, until I could work out which lead made no difference to the existing lumpy idle - the disconnected ignition coil of the faulty one would have no detectable difference, whereas disconnecting the lead for a good coil would cause further idle quality degradation. That was the plan, but it did not go as I had anticipated.

I disconnected the lead on ignition coil on cylinder 1, and the engine remained slightly lumpy. OK. It must be that coil. I wanted to verify, by reconnecting cylinder 1 back, and disconnecting cylinder 2, expecting that the engine will be rougher. But the lumpy idle remained exactly the same. So I reconnected cylinder 2, disconnected cylinder 3, and the idle lumpiness was no different.

I reconnected cylinder 3, so all the cylinders are connected, and still the idle lumpiness is there. How can an engine not have any discernable difference with one cylinder not firing? In a way I'm very impressed by the balance of this V6 motor. Hats off to Toyota for making a super smooth engine, but it's making the job of isolating the faulty ignition coil very hard....

My next step is to remove the coil on cylinder 1 and then remove the spark plug to have a look.

[tempestv8 Member Find all posts View Profile Close tempestv8]

Howdy again, group.

Learnt something about the Prado's ECU - when ignition coil #1 (suspected faulty) was swapped with ignition coil #5, the error codes logged by the ECU then said that both #1 and #5 were faulty. Even clearing the codes with a Scangauge II, the same codes kept coming back seconds after performing the clear. The only way of truly clearing the codes is to disconnect the main battery. After doing just that, the ECU then said that only #5 ignition coil was faulty. So I learnt two things - 1. Scangauge doesn't really clear the codes when it comes to ignition code errors and 2. Disconnecting the battery is the right way of getting the ECU to "forget" which coil is faulty.

Off to get a new ignition coil....

[state50 Lurker Find all posts View Profile Close state50]

These scan gauge II things, where are they available from and how much? Theres not many models of cars that need the battery disconnected anymore to erase fault codes so it seems strange that would be the case with a Prado. Hopefully the coil sorts it for you.

[tempestv8 Member Find all posts View Profile Close tempestv8]

Scangauge can be bought here:

http://www.wooders.com.au/index.php?...products_id=29

If you search this forum you should find some benefits of having such a device.

Not sure why the Scangauge couldn't clear the code permanently - each time I cleared the code, and the warning lights are extinguished off the dash, they reappear after a few seconds.

[state50 Lurker Find all posts View Profile Close state50]

If the fault is still there then it can't be erased. We call it a hard fault compared to an intermittent one.

[datsezy Lurker Find all posts View Profile Close datsezy]

In my Rellim code book P0351 is No.1 ignition coil feedback signal missing. Most likely fault is No.1 ignition coil, especially if it's occurring on petrol & LPG. When erasing diagnostic trouble codes you should do it with the ignition on and engine not running. If after erasing the DTC, it comes back when the engine is started it means that the fault is still present, and will only stay erased when the fault is rectified. Any OBDII/EOBD code reader should read & erase DTC's, stream live power train data and freeze frame data on Australian delivered vehicles from around 2002/2003 as this is when they had to be OBDII compliant. Code readers can be purchased from as little as $20 online, or around $150ish from reputable equipment suppliers.

[RutHunter Junior Member Find all posts View Profile Close RutHunter]

Was this ever sorted? I have the same problem PO351 but engine wont stay running????

My 05 1GR-FE starts and runs for about 2 seconds then cuts out, error coded is PO351. changed the coil and still have the issue. did this thread lead to a cause of the problem?

Howdy group,

Trying to troubleshoot a Prado 120 V6 engine check engine light issue.

The engine seems to be idling slightly lumpy, as if as one of the 6 cylinders is not firing. Starts up fine, no issue with cranking battery but can feel a slight tremor throughout the vehicle.

The amber CEL light is on solid, as well as the two traction control lights next to this warning light.

Using a Scangauge II, I am able to clear the CEL light whilst the engine is running, but a couple of seconds later the CEL light reappears, followed by the traction control lights.

A scan of the computer with the SGII reveals only one error log in the ECU - a P0351 error code. I believe this translates to ignition coil "A", whatever that means.

Has anyone seen this problem before. I have unplugged the wiring loom that connects to cylinder 1, checked that it's clean and refitted it back snugly. I believe cylinder 1 is the first cylinder nearest to the engine air cleaner box release latches.

Any help would be greatly appreciated. It could well be a faulty ignition coil but instead of replacing parts, if there's a way of diagnosing the problem better, I'd like to find out how.

Vehicle has around 180,000 kms on it, and has never been offroaded. All highway driving. Sequential LPG fitted 4 years ago, but the lumpy idle occurs irrespective of whether running on petrol or LPG, so I am presuming that the fuelling system is OK.