P0174 Lean Code - Chasing a leak/gap

A6 All/ S6 All
#1

Hi.

I am chasing a P0174 fault code. report is below…Looks like bank 2 is running lean.

I have an oil leak at the high pressure fuel pump connection to the valve cover gasket. I am thinking that it is the O ring. I am wondering if this is the root cause. Sourcing the O ring presently. Otherwise there are no issues with power, etc. Car runs smooth.

Vehicle: 2009 AUDI S6
Engine: V10, 5.2L; DOHC; 32V; DI
Mileage Reported: 100,000
Report#: 101
Date of Report: 09/07/2018 06:33 AM
Engine/Transmission Diagnostic Trouble Code Information
MIL DTC
P0174 Fuel System Too Lean (Cylinder Bank 2) Severity Level: Moderate
Quick Code Summary:
Code P0174 indicates that the Bank 2 System is too lean (not enough fuel) for a predetermined period of
time.
This condition will prevent the vehicle from running at its optimum efficiency and fuel economy may
suffer.
The engine must have a correct air/fuel ratio to optimize emissions, power and economy.
Conditions For Setting This Code:
Key on or engine running, all electrical components off and coolant temperature at least 80 degrees
Celsius; and the ECM detected the Bank 2 Fuel Control System reached its lean correction limit
Possible Causes:
Air leaks after the MAF sensor, or leaks in the PCV system
Exhaust leaks before or near where the HO2S is mounted
Fuel injector(s) restricted or not supplying enough fuel
Fuel pump not supplying enough fuel during high fuel demand conditions
Leaking EGR gasket, or leaking EGR valve diaphragm
MAF sensor dirty (causes ECM to underestimate airflow)
Vehicle running out of fuel or engine oil dip stick not seated
Technical Service Bulletins: 3
OEM#s Issue Date TSB Description Type
A011309 6/21/2013
01 MIL on, gasoline quality (DTC
P0300 or P030x, lean condition
DTCs)
Technical
A001001 2/5/2010
01 MIL on, gasoline quality (DTC
P0300 or P030x, lean condition
DTCs)
Technical
A000904 4/20/2009
01 MIL on, gasoline quality (DTC
P0300 or P030x, lean condition
DTCs)
Technical
Copyright © 2018 IEC. All Rights Reserved.
Portions © 2012 Cengage Learning. All rights reserved. Used under license.
Report 09/07/2018
06:33 AM
Stored Codes
P0174 Fuel System Too Lean (Cylinder Bank 2)
Conditions For Setting This Code:
Key on or engine running, all electrical components off and coolant temperature at least 80 degrees
Celsius; and the ECM detected the Bank 2 Fuel Control System reached its lean correction limit
Possible Causes:
Air leaks after the MAF sensor, or leaks in the PCV system
Exhaust leaks before or near where the HO2S is mounted
Fuel injector(s) restricted or not supplying enough fuel
Fuel pump not supplying enough fuel during high fuel demand conditions
Leaking EGR gasket, or leaking EGR valve diaphragm
MAF sensor dirty (causes ECM to underestimate airflow)
Vehicle running out of fuel or engine oil dip stick not seated
Technical Service Bulletins: 3
OEM#s Issue Date TSB Description Type
A011309 6/21/2013
01 MIL on, gasoline quality (DTC
P0300 or P030x, lean condition
DTCs)
Technical
A001001 2/5/2010
01 MIL on, gasoline quality (DTC
P0300 or P030x, lean condition
DTCs)
Technical
A000904 4/20/2009
01 MIL on, gasoline quality (DTC
P0300 or P030x, lean condition
DTCs)
Technical
Copyright © 2018 IEC. All Rights Reserved.
Portions © 2012 Cengage Learning. All rights reserved. Used under license.
Pending Codes
P0174 Fuel System Too Lean (Cylinder Bank 2)
Report 09/07/2018
06:33 AM
Conditions For Setting This Code:
Key on or engine running, all electrical components off and coolant temperature at least 80 degrees
Celsius; and the ECM detected the Bank 2 Fuel Control System reached its lean correction limit
Possible Causes:
Air leaks after the MAF sensor, or leaks in the PCV system
Exhaust leaks before or near where the HO2S is mounted
Fuel injector(s) restricted or not supplying enough fuel
Fuel pump not supplying enough fuel during high fuel demand conditions
Leaking EGR gasket, or leaking EGR valve diaphragm
MAF sensor dirty (causes ECM to underestimate airflow)
Vehicle running out of fuel or engine oil dip stick not seated
Technical Service Bulletins: 3
OEM#s Issue Date TSB Description Type
A011309 6/21/2013
01 MIL on, gasoline quality (DTC
P0300 or P030x, lean condition
DTCs)
Technical
A001001 2/5/2010
01 MIL on, gasoline quality (DTC
P0300 or P030x, lean condition
DTCs)
Technical
A000904 4/20/2009
01 MIL on, gasoline quality (DTC
P0300 or P030x, lean condition
DTCs)
Technical
Copyright © 2018 IEC. All Rights Reserved.
Portions © 2012 Cengage Learning. All rights reserved. Used under license.
P1075
P1077
Freeze Frame Information
Report 09/07/2018
06:33 AM
Parameter Description Results
DTC for which Freeze Frame was Stored P0174
Fuel System 1 Status Closed Loop
Fuel System 2 Status Closed Loop
Calculated LOAD Value 25.49 %
Engine Coolant Temp 213.80 °F
Short Term Fuel Trim - Bank 1 3.13 %
Long Term Fuel Trim - Bank 1 -0.78 %
Short Term Fuel Trim - Bank 2 2.34 %
Long Term Fuel Trim - Bank 2 -3.91 %
Engine RPM 650.50 rpm
Vehicle Speed Sensor 0.00 mph
Ignition Timing Advance #1 Cylinder 5.00 °
Intake Air Temperature 140.00 °F
Air Flow Rate Mass Air Flow Sensor 0.46 lb/min
Absolute Throttle Position 12.94 %
Commanded Secondary Air Status Atmosphere / Off
Time Since Engine Start 284 sec
Monitor Status

#2

Welcome to the forum. Glad to have you.

If I’m reading your data shot information correctly it looks like you have some stored code that were left in the ECU. Your LTFT data looks fine and dosent indicate that there is a full time issue.

I would clear out all of these codes and drive for a few days see if it comes back. Did you have a CEL on the dash for this…

Also out of all the work on the car what major maintenance work have you done in say the last year or so.

#3

Thanks Justin.

I have been following most topics on here and thankfully have not had any issues.

Regular maintenance, oil change, plugs and filters.

I am pulling the car off the road for a couple of weeks to complete a carbon clean and bushing changes. Have been through the carbon cleaning with my other cars.

I have cleared the CEL, like I mentioned this is intermittent. I will replace the O ring ($14 from Audi picked up today). My guess is that between the oil leak there is some air or oil mixing with the fuel, or even air contaminating the valve cover…I will update if this fixes the issue.

I will be doing a resonator delete in the next while as well. Still playing around with the right brake combination…currently EBC Red Stuff…not overly pleased with their performance, but brake dust is way down.

–Jeff

#4

Doing a carbon clean and getting under the intake allows you to really check all the vac lines and PCV system. ITs a great time to look all of that over all the problem areas.

#5

Lean Code issue resolved!

O ring on left bank HPFP was totally split and the source of the oil / air leak into the valve cover.

Now under load and normal use, no code issues.

Getting the car ready for winter running, and will have the Carbon clean set up for March/April of 2019.