Fuel Trim Bank Codes

[glassjoe]

2004 E53 X5 3.0, 117K miles

Hello, all. I recently had my Service Engine Soon (SES) light come on and instead of going to Autozone for a read, I recently bought a cheap OBDII reader (Creator C310 BMW Multisystem Scan Tool) on Amazon to see what codes it was throwing. They are:

E4 Fuel Trim Bank 2, Permissible Range Exceeded
E3 Fuel Trim Bank 1, Permissible Range Exceeded

I'm relatively mechanically inclined and would like to try and resolve this myself without going to a shop. I bought this '04 X5 with 106K on it and it now has 117K miles on it and has run well to this point (besides an oil pan gasket I had to have replaced). Upon start, it runs a little rough at idle but smooths out when I'm driving. I've cleared the codes and within 1 drive to work the light comes back on and the codes are the same.

I did some Google searches and didn't really find a smoking gun on what these codes are indicating is specifically wrong. I have cleaned the MAF with cleaner but that didn't do anything. I've read where it can be O2 sensors, the DISA, vacuum leaks, etc., but what I was hoping to find is a methodical approach to resolving the issues instead of throwing parts at it in an attempt to see what works. My son has a 2002 E53 so I thought about swapping the MAFs to see if that makes any difference.

If anyone has any suggestions on a systematic approach to take in trying to resolve this issue it would be greatly appreciated! Thx

[upallnight]

Have you look at real time data? E4 and E3 trouble codes doesn't tell me if you have a lean or rich condition. Perhaps a generic scanner which can display/log real time data will be more helpful.

[glassjoe]

I'll try and see what I can find tonight. the OBDII scan tool I have was made specifically for the E53 and some other BMW and Mini models, so it should provide more detail in some mode. I just got it and am not proficient at seeking out specific data so I'll do some digging tonight and report back. Thx

[upallnight]

E3 - O2 sensor adaptation limit, Cyl#1-3
E4 - O2 sensor adaptation limit, Cyl#4-6

Don't know if this is referring to pre-cat sensors or post-cat sensor. Live data will tell if the sensors are working or dead. Voltage for precat sensor should fluctuate as the mixture is adjusted by the 02 sensor. If the voltage doesn't fluctuate that means the sensor is dead.

Post cat sensors should show almost a constant voltage, If there is no voltage the sensor is dead. Actual short term and long term fuel trim data will show you if you have a rich or lean condition. Without live data it is just a crap shoot as to what is wrong. You might as well throw parts at it with the parts cannon.

[glassjoe]

Upallnight,

So I got some more data for you to look at. It appears all sensors are functioning because they are giving a voltage reading. As far as voltage fluctuation, all sensor positions fluctuated when I depressed the gas pedal. All 4 seemed to react similarly to those inputs.

I also took a shot of the MAF data but have no real idea what I am looking at.

Can you glean any info from these pictures? Thanks!

[upallnight]

Not use to that type of scanner. A graph of the short term and long term fuel trims would be helpful. I use Torque, OBD Fusion on my android phone and tablet to monitor short and long term fuel trims to determine if I have a lean condition or a rich condition.

Multiplicative mixture adaptation: This adaptation is referred to as “long term fuel trim”. This value is measured in percentages and can occur in the positive or negative values. This adaptation occurs during part-load driving conditions.
Excessively positive multiplicative adaptation values indicate lean condition. Some common causes are:
MAF malfunction, incorrect signal information sent to the ECM
Low fuel pressure, faulty fuel pump
Unmetered air leak, such as torn intake boot, etc
Pressure regulator malfunction
Excessively negative multiplicative adaptation values indicate rich condition. Some common causes are:
Sensor failure that could result in erroneous information to falsely enrich mixture, such as engine coolant temperature sensor or intake air temperature sensor
High fuel pressure, restriction in return line or fault with fuel pressure regulator
MAF malfunction, incorrect signal information being sent to the ECM
Restriction at air intake blocking airflow into engine, such as a clogged air filter

Hint: To determine if the MAF is sending incorrect information to the ECM, check the additive and multiplicative mixture adaptations. When the mixture adaptations are contradicting each other, this indicates that the MAF is faulty and sending incorrect signal information.

Hope this help.

[upallnight]

Your additive mixture adaptation shows a positive number which would indicate a lean condition, so the ECM or DME will be adding fuel to the mixture
but you Multiplicative mixture adaptation: shows a negative percentage which indicates a rich condition so the ECM or DME will be taking away fuel from the mixture.

I would look at the MAF for starter. If you do replace the MAF don't buy a cheap made in CHINA crap from Amazon or eBay. Better to buy a used Siemens MAF.

[glassjoe]

Originally Posted by upallnight

Your additive mixture adaptation shows a positive number which would indicate a lean condition, so the ECM or DME will be adding fuel to the mixture
but you Multiplicative mixture adaptation: shows a negative percentage which indicates a rich condition so the ECM or DME will be taking away fuel from the mixture.

I would look at the MAF for starter. If you do replace the MAF don't buy a cheap made in CHINA crap from Amazon or eBay. Better to buy a used Siemens MAF.

Being my son has the same model (albeit a 2002) I may just swap MAFs this weekend and see if the issue follows the MAF. I'll report back once that's done.

Thanks for the guidance!

[upallnight]

It will take a drive cycle for the DME to adapt to the new MAF, so don't expect it to happen right away after a swap. I would clear the code and take the X for a drive with a mixture of different speed, some city, some highway, at least a 10 miles drive.

[Scott ZHP]

Have you inspected all of the intake plumbing, from the filter housing all the way back to the throttle body? Rough running at idle suggests an air leak to me.