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Toyota Service
Toyota Service, Toyota Expert
Category: Toyota
Satisfied Customers: 4849
Experience:  30+ Yrs of auto experience, Award Winning Svc. Manager; Just Answer Customer's Choice Award Winner
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2007 Sienna was said to be fine at the dealer but when we

Customer Question

2007 Sienna was said to be fine at the dealer but when we started it she missed and shuddered and the CEL came on. Minutes later she ran fine and did so for the next day or so. Then it seemed that every other day or so the CEL would come on and sometimes misfire badly. I thought it was a bad coil and replaced one to have it run fine for a couple of days but then the problem came back. I couldn't get the problem to consistently go away by moving the new coil. Random P0300x codes no matter where I put the new coil but never any of the back cylinders until. During a deluge all of a sudden she ran poorly and I found all of these codes:
0300 Random misfire. Ignition parts, O2 sensor, EGR valve, camshaft sensor, vac leak, plugged exhaust
0301 Cyl 1 same as above
0302 Cyl 2 same as above
0303 Cyl 3 same as above
0304 Cyl 4 same as above
0352 Cyl 2 coil
0503 Vehicle Speed Sensor On top of trans
0603 Internal Control Keep Alive Memory
5203 Not found
5400 Not Found
5XXX Manufacturer specific
There was a couple a vac hoses that had cracked but I really don't know what they went to and fixing them didn't fix the problem either. She has Denso FK20HR-11 Iridium Long Life Spark Plugs but the one I pulled looked pretty good compared to a new one. Slightly larger gap by eye but still looks almost the same as the new ones. Until the very heavy rain storm I can't remember any code specific to the back cylinders. Always the front there.
Most of the time she runs REAL good, then just on 5 cylinders but she's unpredictable! Is this enough info for a sharp experienced mechanic to diagnose a fix? I'm reasonably handy but loosing touch with these new vehicles! Happier with a '57 Chev!
What's wrong with out 2007 Sienna?
Submitted: 1 year ago.
Category: Toyota
Expert:  Toyota Service replied 1 year ago.

Hello. Welcome to Just Answer. Please allow me to assist you. First, the scanner you are using is not 100% compatible with your Sienna. This can and will lead to false code readouts. I would recommend you get the vehicle scanned by another scan tool. In this case, I suspect coil issues. YOu mentioned replacing a bad coil. Note that non-Genuine Toyota coils will cause the misfire issue you are having. Also note that all of the coils share the same common ground. The problem I think you have are 2 bad coils. When a coil is bad (what exactly happens is the diode that protects the ground circuit is faulty)...When this happens, a ground fault on cylinder 2 will cause a misfire on cylinder 4. This is very common to reoccur when non-Toyota coils are installed, the diode protection is not as good as the factory units. I recommend you have another scan. If you get p0302/P0304, replace coil #2 and drive it. If the misfire continues, swap coils 2 and 4, and drive again. If the codes do not return, do the same thing on any other combination of coils (1 & 3, 3 & 5), etc.

Expert:  Toyota Service replied 1 year ago.

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Customer: replied 1 year ago.
Lord I had a hard time getting to where I could reply! My scanner claims to read all OBDII codes but some were Toyota specific and I can't find info on them. I think I understand about the ground faults but I have to suspicion that the heavy downpour and some water where it shouldn't be could have trigger the other codes, esp the P0503 Vehicle Speed Sensor that you didn't address. I have 2 other scanners coming shortly so I will try them, but I have cleared the codes already. I will also swap the coils but reaching the rears on a Sienna is tricky,
Customer: replied 1 year ago.
Maybe this will help me/us track our exchanges:
OrderID: 16496961-187
Expert:  Toyota Service replied 1 year ago.

If you have a p0503 code you will cruise control issues. You did not mention cruise control problems.

Customer: replied 1 year ago.
I wasn't the driver at the time but I'm certain she would not have been using cruise during the storm. Maybe it was just a coincidence that the other codes popped up during what she called a "deluge" but I have to suspicion... Other problem is the CEL is keeping us from registering so we can no longer drive it on the road other than up and down a mile long road. And it was running for a couple days without tripping the CEL. If the scanner came in today I'll scan again tomorrow and get back to you as soon as some codes manifest.
Expert:  Toyota Service replied 1 year ago.

Ok. Please clear all of the codes, then re-run the scan.

Customer: replied 1 year ago.
Got my new scanner (2 actually!) and I was surprised by what I read. None of the manufacture specific codes, just:P0300 Random misfires
Codes for each cylinder
Codes for coils 2, 4 & 6.Now I haven't driven it, thought I had cleared the codes, surprised I read any codes and now I don't trust the prior codes from the other scanner... Perhaps I'm starting all over! Maybe the deluge had nothing to do with anything if the prior scanner was giving me bogus codes!?!Don't think the 2007 has a cam sensor, so what would affect all the front cylinders but not the rear?
Customer: replied 1 year ago.
Meant to say what would trigger codes for the front coils only and misfires on all cylinders. I've pulled a plug and compared it to new. Slightly less gap by the eye but not bad. Odd thing it runs great and then like it's running on only five. Then again great and then not and all without me doing anything! If it ran poorly most of the time and then got worse I'd understand, but she's just fine and then she's a unbalanced 5 cylinder.What's next? I can drive it up and down the road a bit but I doubt anything will happen in just a few miles... What would be so intermittent?
Expert:  Toyota Service replied 1 year ago.

Sorry for the delay. I still think you have bad coils, in the respect that you are leaking coil voltage into the ground circuit. I would get a new Toyota coil and insert it into #2, clear the codes and drive it. If the code reappear, swap #2 to #4 and retest. Either you have bad coils (the coil code is the proof) or, you have a sticking variable valve timing actuator or variable valve timing oil control valve issue. Do the coil movement first; the V V T issue is really tricky to diagnose because you need to be able to manually control the V V T oil control valve to test.