BMW E90 N46 320I LCI Intermittent loss of power - FAULT CODE 2A77 & 2A56?

[Charldon73]

Hi All

I am looking to gather some opinion on a rather annoying fault I have. Let me start with the issue:

Issue:
Intermittent, pronounced loss of power on acceleration. (NO CHECK ENGINE LIGHT)

Normally when i apply Full throttle to accelerate Engine is running 100% until 3800 rpm then it feels like it will stall or out of Petrol for as long as the accelerator is pressed or for a few seconds. Let off accelerator and reapply and engine accelerates normally.

this only happens when i apply full throttle Note: this does not happen all the time (Intermittent)

car is very well maintained and always serviced every 10000km

i bought INPA to do some troubleshooting and was really surprised to only find 2 fault codes stored on the DME/DDE (2A77 & 2A56) and some codes on FRM but its the basic blown lights that is stored there is no other stored codes and was last cleared 3 years ago.


MY control unit is MEV17N46

Fault Code

Code​	Label​	ECU Variant​	ECU Label​	Fault Info​

2A77​

DME: Oxygen sensor behind catalytic converter, ageing​

mev17n46​

Engine electronics​

View​

2A56​

DME: Oxygen sensor heating behind catalytic converter, function​

mev17n46​

Engine electronics​

Fault Code Description : 2A77

1. Oxygen sensor after catalytic converter, ageing
2. O2 Sensor Circuit Slow Response (Bank 1 Sensor 2)
(Fault Impact)
3. Overrun fuel-supply cutoff Engine running
4. Inspect connection between DME and oxygen sensor behind catalytic converter,
replace oxygen sensor behind catalytic converter, replace DME

Fault Code Description : 2A56

1. Oxygen sensor heating after catalytic converter, function
2. O2 Sensor Heater Circuit (Bank 1 Sensor 2)

What is really interesting is on Code 2A77 (Fault impack) it states "Overrun fuel-supply cutoff Engine running" can it be that the O2 sensor is sending the wrong info to the ECU thus the engine cuts fuel to the engine to protect it self, witch will explain the intermittent loss of power.

accordingly to other Forums the post cat sensors isn't supposed not do anything like this because it only checks the health of the Cat or can it cause this problem.

it cant be a the Timing, VANOS or Eccentric Shaft Sensor as there is no Fault codes stored and i have brand new VANOS solenoids
also note 2A77 code on other E90 can be a VVT issue depending on their ECU Variant but not for mine.

Hope this can help me or someone.

 

[Manfred]

Hi All

I am looking to gather some opinion on a rather annoying fault I have. Let me start with the issue:

Issue:
Intermittent, pronounced loss of power on acceleration. (NO CHECK ENGINE LIGHT)

Normally when i apply Full throttle to accelerate Engine is running 100% until 3800 rpm then it feels like it will stall or out of Petrol for as long as the accelerator is pressed or for a few seconds. Let off accelerator and reapply and engine accelerates normally.

this only happens when i apply full throttle Note: this does not happen all the time (Intermittent)

car is very well maintained and always serviced every 10000km

i bought INPA to do some troubleshooting and was really surprised to only find 2 fault codes stored on the DME/DDE (2A77 & 2A56) and some codes on FRM but its the basic blown lights that is stored there is no other stored codes and was last cleared 3 years ago.


MY control unit is MEV17N46

Fault Code

Code​	Label​	ECU Variant​	ECU Label​	Fault Info​

2A77​

DME: Oxygen sensor behind catalytic converter, ageing​

mev17n46​

Engine electronics​

View​

2A56​

DME: Oxygen sensor heating behind catalytic converter, function​

mev17n46​

Engine electronics​

Fault Code Description : 2A77

1. Oxygen sensor after catalytic converter, ageing
2. O2 Sensor Circuit Slow Response (Bank 1 Sensor 2)
(Fault Impact)
3. Overrun fuel-supply cutoff Engine running
4. Inspect connection between DME and oxygen sensor behind catalytic converter,
replace oxygen sensor behind catalytic converter, replace DME

Fault Code Description : 2A56

1. Oxygen sensor heating after catalytic converter, function
2. O2 Sensor Heater Circuit (Bank 1 Sensor 2)

What is really interesting is on Code 2A77 (Fault impack) it states "Overrun fuel-supply cutoff Engine running" can it be that the O2 sensor is sending the wrong info to the ECU thus the engine cuts fuel to the engine to protect it self, witch will explain the intermittent loss of power.

accordingly to other Forums the post cat sensors isn't supposed not do anything like this because it only checks the health of the Cat or can it cause this problem.

it cant be a the Timing, VANOS or Eccentric Shaft Sensor as there is no Fault codes stored and i have brand new VANOS solenoids
also note 2A77 code on other E90 can be a VVT issue depending on their ECU Variant but not for mine.

Hope this can help me or someone.

Did you find the problem?

I have the same issue...

 

[DarrylvanNiekerk]

I had an issue slightly similar to this (e90 320i pre LCI) when trying to get the car running after a rebuild. I found the post 02 sensors were not connected and the car was misfiring.

I would hazard a guess that if you looked at your live stream data from your 02 sensors you will most likely find the fuel trims are quite high - either pulling or pushing fuel.

This could be caused by the 02 sensors and they can only adjust fuel trims to a point. You are asking much higher fuel load at those rpm at WOT and it probably can't supply so it is going into limp mode for a moment seemingly.

You may have an issue which coincides coming from sparks or injectors which may be incorrectly fueling or even a vacuum leak post MAF and MAP.

Might be an idea to swap 02 sensors around and see if fuel trims change. If necessary you might have to replace them as the don't really clean up well.