2007 xc70 OBD code help

[Durenol]

Car is an errand-mobile that isn't driven much and only has 51K on it. Yesterday the check engine light came on. Did a full scan at the local gas station and their code reader reports only two codes:

212C Long Term Fuel Trim, Bank 1
21EC Long Term Fuel Trim, Bank 1

These codes seem specific to Volvos and I'm having trouble finding info about what they actually mean, what the possible causes are, and what sort of price range I'm looking at. Google results suggest all sorts of random stuff, a crack in a hose somewhere, a dying fuel pump, a dead O2 sensor, etc.

I have no idea where to start and I don't really want to pay a shop to go on an exploratory mission swapping out half the car.

[abscate]

Do you have a scanner that can read fuel trims? Seeeing how they misbehave gives clues to the problem(s)

Having just come from the Volvo dealer and seeing a labor rate of $295 per hour, no one can afford fishing expeditions

[Vova585]

Do you have a scanner that can read fuel trims? Seeeing how they misbehave gives clues to the problem(s)

Having just come from the Volvo dealer and seeing a labor rate of $295 per hour, no one can afford fishing expeditions

Sorry that I am off topic..$295? Was it a typo? I hope it is a typo and it was $195. It is still expensive, but not at the rate of $295. My local dealer(Garber Volvo) is at $185. Most firestones are at $160-180, so i better pay dealer if need be.

Back to the topic. Get yourself icarsoft volvo tool or topdon entry level tool( dangle that connects to the phone; around $130 on amazon) and erase the codes. Meanwhile if the car drives great without signs if misfire- change to nonethanol fuel, put some good injector cleaner in a tank and take this car a for a long nice drive with some "Italian tune up" . Preferably change the oil too if it was not done for a long time. Then with the help of your own diagnostic tool look into global OBD side and see the codes. Most of the times you dont need volvo specific codes and OBS is just enough.

[Durenol]

Do you have a scanner that can read fuel trims?

No. Honestly I know next to nothing about OBD scanners. The gas station and the auto store down the street both do free scans so I've never bothered to buy any of my own devices. The gas station's device was this giant ipad-looking thing, I guess I can ask them what it can do.

Sorry that I am off topic..$295? Was it a typo? I hope it is a typo and it was $195.

The closest dealer to me charges 280, so probably not.

Get yourself icarsoft volvo tool or topdon entry level tool( dangle that connects to the phone; around $130 on amazon) and erase the codes. Meanwhile if the car drives great without signs if misfire- change to nonethanol fuel, put some good injector cleaner in a tank and take this car a for a long nice drive with some "Italian tune up" . Preferably change the oil too if it was not done for a long time. Then with the help of your own diagnostic tool look into global OBD side and see the codes. Most of the times you dont need volvo specific codes and OBS is just enough.

Well, again, as far as I know these two codes are the ONLY two codes it's thrown. The guy at the gas station was showing me the ipad and going down the list and literally everything else was a green checkmark. The car otherwise seems to drive fine I think, the check engine light is the only indication something is wrong.

I can ask them do do a reset, but from what little I can tell via google, the computer does some kind of longterm average on the fuel mix ratio and when that average gets out of range these codes fire as a warning. In other words I believe this is a problem that's been building for a while not a one off random incident.

I'm mainly looking to see if anyone knows anything more specific about these codes and what sorts of problems typically trigger this. I'm hoping someone can suggest something for me to look at with a flashlight or listen to on the highway or whatever. (Ideally I'm hoping someone will say I can fix it myself with a $40 part and a screwdriver, but I know that's dreaming in this day and age).

[Vova585]

My honest answer: if you want to keep this car for a long long time, and you dont want to spend a fortune on maintenance and repair(assuming you are an able body adult) it will be in your best intrest to obtain "basic" scanner as suggested above. With $280 labor rate, $140 tool start to look like a cheap investment. If you have a lot of other brands, get topdon, if only 50k volvo, then icarsoft is very DIY friendly. Another alternative is to post your location and maybe some members will suggest great INDY volvo knowledgeable shop that can help. Fuel trims are calculated based on O2 sensor information. Your problem might be as easy as too much fuel in the oil, dirty upstream O2, issues with clogged injectors...same as above-quality fuel nonethanol(especially if you dont drive it much), injector cleaner, oil change, road trip with Italian tune up.

[Durenol]

it will be in your best intrest to obtain "basic" scanner as suggested above.

Well, like I've said, I can already get free scans from multiple places whenever I want them so I see little point in paying for any sort of "basic" scanner. Obtaining the error codes is not the problem here, I already have the codes, I'm trying to figure out what they mean and what part of the car to look at/listen to for more info.

Fuel trims are calculated based on O2 sensor information. Your problem might be as easy as too much fuel in the oil, dirty upstream O2, issues with clogged injectors...same as above-quality fuel nonethanol(especially if you dont drive it much), injector cleaner, oil change, road trip with Italian tune up.

The car is mostly for errands and such. It typically takes around 2-5 trips a month, with each trip being maybe 15-30 minutes each way, or thereabouts. This driving pattern has held for the majority of the car's life and it's never thrown any fuel trim codes before. You seem to know at least something about this, how long is the running average that the computer calculates? Like, is it the last 10 hours of engine-on time? The last 30 days of clock-time? etc. Knowing the length of the measurement might give me a clue when this started.



A couple questions for anyone:

- Is this something that could have been caused by something as simple as a bad tank of gas? The car has only ever been filled with premium grade (91 AKI or better) and typically only a half or a third of a tank at a time, if that matters.

- I was always told that while fuel stabilizers work for things like lawnmowers and snowblowers that aren't used for months, any form of fuel "cleaner" was mostly a scam because gas itself is inherently already pretty good at cleaning stuff. And at worst sometimes they can corrode internal seals. Does this stuff actually work?

- I've seen a couple references now of O2 sensors. Do these commonly go bad after time? How hard/expensive are they to replace on this model?

[Vova585]

There is nothing worse for the car than not being used. Second killer- short infrequent trips. Fuel has 10% ethanol on average and it is not the best thing for your fuel injection system. Nonethanol is superior option for your situation and does not require any fuel stabilizers. I still recommend you to try aproach as was suggested previously. I am suspecting your issues might be resolved after good trip where all systems have chance to work during real demand. In terms of your view on scanners- free is free, and value is little. If you have no knowledge ar willingness to learn new to you information and you dont want to invest into diagnostic tools...better go to a good mechanic. If you are interested to make sure you have a better understanding of the problem- invest into diagnostic scanner. This way we can help you better narrow the issue based on data from o2 sensors, coolant temp sensor, maf sensor...in terms of 02 sensors cost..probably close to $200 each(2 of them) with 0.7 hours of labor cost per each.

[abscate]

Once the car goes closed loop, it is adjusting the short term fuel trim, or injector length , by =-20% or so to keep the amount of oxygen in the exhaust mixture optimum. The short time time constant is something like 1 second=d. The long term trim is calculated by averaging the short term over minutes
If the short term trim is consistently -10% , for example , then the long term trim will slowly converge to -10% and the short term trim will move closer to 0%

Once the long term trim reaches 20%, a code is set for system too lean or rich, as it has run out of adjustment range.

By looking at the actual fuel trim values as rpm’s change , you can detect vacuum leaks, leaking fuel injectors, bad fuel pressure , etc, so that’s great diagnostic information.

Many codes don’t set immediately , they detect a persistent set of conditions before setting a code, and the trim code is one if these. On a better scanner, a code will “pend” before it trips the check engine light

I’m not seeing 212C nor 21EC in the Volvo table of ECM codes. Probably the scanner software is mapping to done other database .you want codes in the format p-xyyy or ECM-xxxx,

On p codes x=0 is a SAE stAndard code , the same for all car makers. X=1,2,3 are manufacturer specific codes. Another plug fir having your own scanner, get a used one of ebay or one of the blue tooth ones that can read fuel trims

You are probably coding p0171 for lean fuel trim due to a vacuum leak

[Durenol]

If you are interested to make sure you have a better understanding of the problem- invest into diagnostic scanner. This way we can help you better narrow the issue based on data from o2 sensors, coolant temp sensor, maf sensor...

The thing you're not getting here is that if someone can just tell me what to actually look for I can go to one of the places near me and have them do it for free. There's no point in dropping money on a scanner to do the exact same thing I can already do for free. If you tell me I need to look for something specific and none of the shops' scanners can do it, THEN I'll consider buying a specialized one of my own.

By looking at the actual fuel trim values as rpm’s change

OK thank you, this info actually helps. So I'm looking for a live readout as someone sits in the car and revs the engine? What format readout am I looking for here? Is this some sort of X/Y line graph or an ordered list of changing numbers or something?

Many codes don’t set immediately , they detect a persistent set of conditions before setting a code, and the trim code is one if these. On a better scanner, a code will “pend” before it trips the check engine light

Well that ship has sailed at this point. I'm assuming based on your description that whatever problem is causing this has been going on for a while then (as opposed to relatively recently due to a bad tank of gas or such)?

I’m not seeing 212C nor 21EC in the Volvo table of ECM codes. Probably the scanner software is mapping to done other database .you want codes in the format p-xyyy or ECM-xxxx,

This helps too, and might explain why I'm not seeing much with a google search.


In general with regard to fuel trim issues, how safe is it to keep driving the car? Like, can it be driven around for a couple weeks to different shops while trying some fuel cleaner in the tank, or is that asking for trouble? I'm unclear how serious things like a clogged injector or vacuum leak are for this model.

[matthew1]

I can't think of much a fuel trim problem would cause except, very eventually, ruined cat convertor (rich) or burnt valve (lean), or a failed emissions inspection. It's ok for a short while.

From Grok AI:

ECM-212C and ECM-21EC map to: P2177

P2177 — System Too Lean Off Idle (Bank 1)

Volvo specific meaning:

• ECM-212C → Long-term fuel trim, bank 1: Signal too high
• ECM-21EC → Adaptive heated oxygen sensor control, bank 1: Signal too high

Both codes indicate the ECM is seeing a persistently lean condition on Bank 1 and is adding too much fuel via long-term fuel trim.

Common Causes (especially on Volvo P2 2.5T models):

• Intake leaks after the MAF sensor (most common)
• Vacuum leaks
• Exhaust leaks before the upstream O2 sensor
• Low fuel pressure (fuel pump, filter, regulator)
• Faulty upstream O2 sensor (Bank 1)
• Dirty or failing MAF sensor

Note: These two codes (212C + 21EC) very frequently appear together on 2005-2008 Volvos.