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[jandroa]

Hi everyone! Opel Omega 2.6 V6 (Y26SE) owner here. Some weeks ago my Omega check engine light came on. The errors codes were P0170 and P0173 (Fuel Trim Malfunction Bank 1 & 2). I inmediately took the car to the official Opel workshop in my town. They had the car for about a week and did all sort of tests, but they didn't found anything wrong, so they just erased the error code to turn off the check engine light. I was told that the lambda sensor data was OK. They returned the car to me, and only 50km later, the check engine light is back.

The car is running right and there is nothing wrong in terms of functioning, performance or noises.

Should I be concerned about it? Do you have any experience with this issue and know what could be the reason behind the check engine light?

I would be grateful if you could point me in the right direction.

Thank you in advance.
Alex.

Edit: Add more information.

[TheBoy]

Does the car run on LPG? If so, might need to get LPG remapped.

Does the car have an aftermarket oiled air filter? If so, pop a stock one on.


Otherwise, are the trims high or low (positive or negative on a 2.6/3.2, or less or more than 127 on an older one).  Ideally you need to read the live data off it for the LTFT, and also the MAF

If you don't have the capability to obtain live data, check for air leaks in the intake system, ir exhaust leaks around or near the manifolds.

[jandroa]

Thank you for the suggestions!

The car runs on petrol (E10) and as far as I know the air filter is original (last change was done at the official Opel workshop a couple of years ago).

Today I got a cheap scanner to read some live data from the OBD2 port. The STFT was fine, making small corrections but always very close to 0.0 (both above and below zero). However, the LTFT showed the value at 25 which I think is very high. I guess this is the maximum value until the check engine light activates. The strange thing is that the car behaved well, with no apparent signs of air leaks.

The MAF sensor values were fine  (I am far from being an expert), 2.3 at idle.

Thank you!

[grifter]

My 2.6 runs on E10 ok, but it seemed that the lamdba code came up a lot more with e10, so I just use e5, if on occassion it does come on I just disconnect the battery for a while. Fuel consupmtion also much higher on E10.

[TheBoy]

The MAF sensor values were fine  (I am far from being an expert), 2.3 at idle.

The correct reading for a 2.6's MAF at idle is about 12kg/hr, which is:
12,000/60 = 200g/min
200/60 = 3.33g/sec
(assuming my maths is right)

2.3 (presumably) g/s = 8.2kg/hr, which seems a little low to me.  Which usually means unmetered air getting in by not going through MAF (or MAF has developed a fault, though Omega MAF's are bomb proof if not oiled by a filter or sprayed with cleaners)


And, yes, around 25% of trim (+ve or -ve) is where it brings on a trim malfunction.

[jandroa]

My 2.6 runs on E10 ok, but it seemed that the lamdba code came up a lot more with e10, so I just use e5, if on occassion it does come on I just disconnect the battery for a while. Fuel consupmtion also much higher on E10.

That is interesting, I never though E5 comsumption would be lower than E10. I will give a try!

The correct reading for a 2.6's MAF at idle is about 12kg/hr, which is:
12,000/60 = 200g/min
200/60 = 3.33g/sec
(assuming my maths is right)

2.3 (presumably) g/s = 8.2kg/hr, which seems a little low to me.  Which usually means unmetered air getting in by not going through MAF (or MAF has developed a fault, though Omega MAF's are bomb proof if not oiled by a filter or sprayed with cleaners)


And, yes, around 25% of trim (+ve or -ve) is where it brings on a trim malfunction.

That is a little bit confusing to me because the MAF says the airflow is a little low but the LTFT at 25% says it has a lot of air so it's injecting more fuel, isn't it? As you said, maybe the unmetered air is not passing through the MAF or the MAF has developed a fault.

I will ask the mechanic to check the MAF, the lambda sensor and if there is any point where air can enter, a damaged hose or something like that.

Thank you!

[TheBoy]

That is a little bit confusing to me because the MAF says the airflow is a little low but the LTFT at 25% says it has a lot of air so it's injecting more fuel, isn't it? As you said, maybe the unmetered air is not passing through the MAF or the MAF has developed a fault.

Its a petrol engined closed loop system so...

It injects fuel based on incoming air.  The lamdas detect its running too lean, because more air is coming in that it thinks, so ecu increases trim (increases injector duration).

[mong00sehun]

hi,
i have a 2.6 too, and i had this error code around one month ago
this occoured when i had a just little amount of fuel in the tank and i drove on serpentine roads, when i think the fuel is was too low, and and the pump cannot recivie the right quantity.
i refulled and i dont have this code anymore

[jandroa]

Its a petrol engined closed loop system so...

It injects fuel based on incoming air.  The lamdas detect its running too lean, because more air is coming in that it thinks, so ecu increases trim (increases injector duration).

Ok, I will erase the error code and check again if the LTFT rises.

hi,
i have a 2.6 too, and i had this error code around one month ago
this occoured when i had a just little amount of fuel in the tank and i drove on serpentine roads, when i think the fuel is was too low, and and the pump cannot recivie the right quantity.
i refulled and i dont have this code anymore

Thank you for your information, I will ensure that my tank is not too low 

[jandroa]

Hi everyone, after clearing the error code and driving for a few hours, the check engine light does not come on, but if I connect the OBD scanner it shows me the error codes P0170 and P0173 again.

The car is running as always, there are no significant changes in rpms at idle, no loss of power when accelerating...nothing unusual.

Checking the scanner measurements again it shows me the following data:

RPM (at idle): around 650rpm
MAF (g/s): 3.5
STFT1 and 2, changing between -3% and 3%.
LTFT 1 and 2: 25%
O2B1S1: changing between 0,085 and 0,900
O2B1S2: around 0,700
O2B2S1 and S2: similar values than B1.

If the car had an air leak, shouldn't it be noticeable in the rpms at idle, or even when the car moves? Can a faulty sensor bring the LTFT to 25% even if the car is running properly?

Thank you!!

[jandroa]

Additional info: I have seen that besides de STFT is ok at idle, as soon as the rpm goes higher, the STFT goes above 14-15, making the LTFT reach 25 at the long term.

[TheBoy]

Reset fault codes (which on a 2.6, if there is a stored code, should reset the BLMs)

Confirm LTFT is 0%, and stays at 0% when idling for a few minutes.

Increase revs, and see if LTFTs rise. And if both banks rise at around same rate.


I'm wondering if its sucking unmetered air, but only at higher revs.

[TheBoy]

Also worth checking that the B!&2 Sensor 1's are flicking between rich and lean at about 1Hz once it goes closed loop.  On the Tech2, this figure is called ratio, but might be called something else on other scanners.

If its not alternating, or doing so slowly, this can be a sign of a tired sensor.

[jandroa]

Reset fault codes (which on a 2.6, if there is a stored code, should reset the BLMs)

Confirm LTFT is 0%, and stays at 0% when idling for a few minutes.

Increase revs, and see if LTFTs rise. And if both banks rise at around same rate.


I'm wondering if its sucking unmetered air, but only at higher revs.

This is exactly how it worked, resetting the fault codes put the LTFT at 0%. When idle, LTFT remained at 0% and STFT varied between -3%, +3%. When I increased revs to 2000 and held it for about three minutes, STFT went up to 14-18%, and LTFT began to increase, both banks at the same rate, up to 0,8%.

As you said, it seems to be sucking unmetered air only at higher revs, at idle it's ok.

Also worth checking that the B!&2 Sensor 1's are flicking between rich and lean at about 1Hz once it goes closed loop.  On the Tech2, this figure is called ratio, but might be called something else on other scanners.

If its not alternating, or doing so slowly, this can be a sign of a tired sensor.

As for the B1&2 sensor, I am afraid my cheap scanner is not giving me the ratio or anything like that, just the voltage.

[polilara]

https://www.omegaowners.com/forum/index.php?topic=149556.0;all

If you check this you can see my Y26SE with old and new sensors, mV...