2007 xc70 OBD code help

[Durenol]

P2177 — System Too Lean Off Idle (Bank 1)

So I was able to get more data from the guys at the gas station. This is the exact P code version of the error their scanner shows, description text and all.

He let me dig around in the menus and I found what appear to be the live fuel trim graphs. There were only four of them: a short and three longs. I'm including a pic I took but you'll have to excuse the horrid picture quality since the screen was super hyper glossy and it was impossible to not get massive glare and reflections, so I had to mess with the image in photoshop to make anything visible. I revved the engine back and forth in neutral for a bit so that's what this is showing. I'm assuming the first long running at negative 2.5 with the massive downwards stairstep is the issue.

Any thoughts?

[Durenol]

Also: the check engine light went out on its own without resetting any of the codes. I'm assuming that means it's just barely on the threshold.

[jonesg]

I would still be smoke testing it for vacuum leak.
The hoses under the intake manifold go bad often, feel along the hoses, thats how I found mine. code P2187.

[DavidE7]

That last comment and video from jonesg are good. There are about a hundred places that could have a leak in between the mass airflow sensor and the combustion chamber. A smoke test is the fastest way to find them. Simple smoke testers can be purchased on eBay or at Harbor Freight. Very fancy and expensive ones are available from the tool trucks. There are many instructions on YouTube for making a smoke tester yourself. They are the easiest method for finding a leak. I have found Volvo intake leaks in the carbon canister purge hoses as shown in the video above, at a broken plastic intake pipe, at a turbocharger actuator diaphragm, in very small brake vacuum hose cracks, in the PCV system at the lower connection between the engine block and the trap, and through the edge of a PCV diaphram on a non-turbo car.

The alternative to smoke leak detection is to use air pressure from a bicycle pump or an air compressor and listen for where the leak is coming from. This was the solution I used before the smoke machines were available and it wasted a lot of my time.

Good Luck!

[leapdragon]

I second the advice to get a scanner. Codes are not the only thing you are looking for. You need to be able to observe behavior and read actual data. Like: what are the actual values of the long-term fuel trim? Do they go up or down as you accelerate and/or drive around town? Are they high when you first start and then the get lower as the car warms up?

With a good scanner, you can get this information and much more besides, as the car is running. This tells you more than codes ever will, and will help people here and elsewhere to help you.

For example, from the list above, with a decent scanner you will be able to monitor fuel rail pressure, intake pressure, OBD sensor behavior, etc. Even if you don't take the time to learn what these look like and how they're meant to behave, others can ask you questions about what you see on the screen.

I use a Vgate VLinker, costs about $60 in the US, along with the Torque app for my phone, and have a standard screen set up that watches coolant and transmission temp, fuel trims, fuel pressure, boost, RPM, timing advance, etc. Every time I do an oil change, or more than that if something is misbehaving, I do at least one drive with the app open so I can watch values as I go and spot anything that's looking off.

It's really not that much considering the insight that it gives you. Most important tool in the arsenal to keep a car running IMO.

[ToyoToyo]

Dude, you know who is good at the code diagnostics? AI! I had a p0171 code lean fuel mixture code on my wife's Forester. I bought a cheap scanner off Amazon, asked ai what to look at after explaining my problems and observations. It told me what to screenshot, then I uploaded it back to AI and it found the failing 02 sensor data (it even instructed me to test it under load at 3,000 rpm - thats where the readings really went off)! Paid the local shop to just replace the sensor (it was 30 min job) - and problem's gone!

The problem was bugging us for almost 2 years actually and diagnostics couldn't track it - all they said the car is fine.

[matthew1]

AI is just MVS but faster and without terrible dad jokes.

[ToyoToyo]

Those Volvo specific codes basically point to a lean condition on bank 1, most likely a vacuum leak somewhere after the MAF — spray some carb cleaner around the intake hoses while it's idling and listen for any change in revs.