Error code P0172 VVTLi

[Mikie711]

Found this on the net

http://www.tankota.net/repair/Repair_Ma ... p0171p.pdf

and this

http://nikiforoff.info/free/Toyota%20Ma ... cc4000.pdf

First one is for a Yota engine but not 2zz-GE, second one is for the 2ZZ engine.

Don't know if it's any help.

[robin]

What's interesting with both of these is that a P0172 indicates that the trim is too rich, i.e. the engine is pushing through too much air and the ECU is having to add extra fuel to get it to run at target AFR. The oil ingress could only cause the engine to run richer, which is actually the opposite of what this fault code appears to be implying?!? Or did I read it wrong?

The exhaust gas leak, dodgy Lambda sensor or MAF sensor look very much more likely if my reading is correct.

Not saying it isn't the oil leak, but I would like to understand why!

Cheers,
Robin

[Mikie711]

I think your right for the code quoted the ecu is using short term fueling trim and making the mixture to rich according to the lambda sensor. This would mean that the ecu is reading higher air flow going into the engine than there actual is or it thinks the air is warmer than it actually is. If there was a leak in the exhaust the lambda sensor wouldn't be able to tell it was rich because of the extra O2. Could also be a gubbed lambda sensor. If I am reading it right.
However everything in the list could, one way or another, give the same end result. As for the oil problem, seen and heard of this in VXR's, glazed bores resulting in poor sealing. Would be worth doing a compression and leak off test to confirm or deny.

Mike

[mac]

From what Meatball posted I picked up on that it's a failure of the VVTLi system - the oil pressure is required to operate the valve timing and lift correctly so lack of pressure in that area is affecting the duration etc which is causing a mixture issue.



Mac

[robin]

I just re-read the first link which is clearly saying the opposite to what I thought

HINT:
When the DTC P0171 is recorded, the actual air–fuel ratio is on the LEAN side. When DTC P0172 is
recorded, the actual air–fuel ratio is on the RICH side.
If the vehicle runs out of fuel, the air–fuel ratio is lean and DTC P0171 is recorded. The MIL then comes
on.
If the total of the short–term fuel trim value and long–term fuel trim value is within +30 %, –35 % (75°C
or more), the system is functioning normally.

I.e. it's saying that the actual value coming back from the lambda sensor is showing rich AFR and the fuel trims are backed off as far as they are allowed to go. Reading the fuel trims with the OBDII tool would make sense too.

Mac, if there was an oil leak that reduced oil pressure below acceptable levels at any point in the engine, the oil flowing through the leak would be immense and you would soon run out of oil, or at the very least have a large amount of oil built up somewhere, at which point the pressure would then equalise across the leak and thus pressure would be restored on the other side.

Cheers,
Robin

[Mikie711]

That would point to a faulty MAF or fuel pressure regulator. That's assuming the lambda sensor is OK. Not knowing how much "too rich" the engine is running makes it harder to work out what's knackered. If were me I would check the emissions and run the A/F Control active test which wold mean taking it to someone with a OBDII scan tool. I know just the man up here but that doesn't help you any.

[meatball]

Robin,

New O2 sensor fitted!

[roadboy]

Glad you sorted it mate.

To be honest though, I'd be a bit upset about the other Lambda sensor only lasting 9 months.

Not much you can do though. Things like that are a barsteward to claim against.

Dan

[meatball]

Apparently its very common......some poor parts out there and some odd cars.......
There is one car (not mine thankfully) that kills one every 6 months!

Once again Robin was right.......I must owe him a few now.......