Help with a Long Term Fuel Trim Lean error

[aslan]

Hello

I'm getting a ECM-25 DTC which is "long term fuel trim - lean". I thought it was resolved after I replaced the fuel pressure regulator but it now has come back again for the second time.

First time the engine light came back I thought it was me not resetting the fuel trim adaptation as instructed. I did that and it went away for a couple of days. I also found a loose vacuum hose to the intake hose which I've fixed. I also have cleaned the connector (at firewall) to the front oxygen sensor. The MAF sensor is clean.

There are no other related codes (I do have a siren battery code but it's been there for ages)

The DTC lit up today and I connected my scanner and found the LTFT at +7.5%. It's odd as I thought it would be higher. I'm not sure if that's the default value as VIDA says the fuel trim is disabled when a lean DTC is recorded. After resetting the fuel trim these are some values I pulled up at idle

LTFT 0% (due to adaptation reset just done)
STFT +15 to +24
O2 Volts Bank 1 Sensor 1 - fluctuating from 0.1V to 0.8V. (don't know what this represents)

Prior to the recent DTC, my LTFT was at +4.5%. I'm thinking the STFT is not right.

How do I go about solving this?

Thanks in advance.

[druid]

Mine turned out to be a coil pack, or at least it hasn't come back in over a 1000 miles since changing one of them (4 on the Gdi).

[skyship007]

Might be one of the dreaded O2 fault codes. This gives a description of what they do:
http://www.obd-codes.com/p0156
In short, Oxygen sensors tend to start failing after the cars warranty has expired and cause a check engine light plus some assorted fuel mixture related codes.

This list of Volvo fault codes says it might be the front O2 sensor:
http://forums.swedespeed.com/showthr...onversion-List
BUT, that might be the wrong list!

[960kg]

Originally Posted by aslan

Hello

I'm getting a ECM-25 DTC which is "long term fuel trim - lean". I thought it was resolved after I replaced the fuel pressure regulator but it now has come back again for the second time.

First time the engine light came back I thought it was me not resetting the fuel trim adaptation as instructed. I did that and it went away for a couple of days. I also found a loose vacuum hose to the intake hose which I've fixed. I also have cleaned the connector (at firewall) to the front oxygen sensor. The MAF sensor is clean.

There are no other related codes (I do have a siren battery code but it's been there for ages)

The DTC lit up today and I connected my scanner and found the LTFT at +7.5%. It's odd as I thought it would be higher. I'm not sure if that's the default value as VIDA says the fuel trim is disabled when a lean DTC is recorded. After resetting the fuel trim these are some values I pulled up at idle

LTFT 0% (due to adaptation reset just done)
STFT +15 to +24
O2 Volts Bank 1 Sensor 1 - fluctuating from 0.1V to 0.8V. (don't know what this represents)

Prior to the recent DTC, my LTFT was at +4.5%. I'm thinking the STFT is not right.

How do I go about solving this?

Thanks in advance.

Just a list for you to check!.......ECM-25 is LEAN or RICH!

[aslan]

Originally Posted by skyship007

Might be one of the dreaded O2 fault codes. This gives a description of what they do:
http://www.obd-codes.com/p0156
In short, Oxygen sensors tend to start failing after the cars warranty has expired and cause a check engine light plus some assorted fuel mixture related codes.

This list of Volvo fault codes says it might be the front O2 sensor:
http://forums.swedespeed.com/showthr...onversion-List
BUT, that might be the wrong list!

Thanks! I'll have to some more research on testing the 02. The V40 has 174k km on it.

[aslan]

Originally Posted by 960kg

Just a list for you to check!.......ECM-25 is LEAN or RICH!

Thanks! VIDA is telling me it's a lean fault.

Anyone know of a good way of testing the 02 sensor?

[960kg]

You should really only use the appropriate Vadis/ Vida that applies to your year of manufacture.....in that way you get ALL the relevant information...

You should have these illustrations somewhere?

These are for 2003 B4204T3 turbo motor

[aslan]

Originally Posted by 960kg

You should really only use the appropriate Vadis/ Vida that applies to your year of manufacture.....in that way you get ALL the relevant information...

You should have these illustrations somewhere?

These are for 2003 B4204T3 turbo motor

I'm using VIDA 2013A. And vehicle profile is using my VIN which it recognize. Is that fine?

You DTC list looks the same as I have. And yes I do have these illustrations but took some digging. The fault trace step is not much help

[aslan]

There a lot more info on 02 if I go through the 02 DTC steps. There a whole bunch of these.



And I found your pictures somewhere there. Where is the breakout box they keep referring to?

And if a weak 02 is causing my lean condition, under which fault should I be concentrating on? Low signal, high signal etc? Just to narrow down the troubleshooting steps.

Sorry for the questions! Quite new at this.

[960kg]

I think you will find where you have ECM-18 written 8 times although it says intermediate fault or permanent fault the actual reading when you open each one is identical.....so therefore very easy to sort and not as complicated as they make it look!

I think the breakout box they refer to is Volvo`s scanner which will be plugged in to get the error codes.