P0175 OBDII Trouble Code - System Too Rich (Bank 2)

I have now gotten this OBDII code twice. Once today, and once about 10 days ago. I cleared the error 10 days ago and it just popped back up today.

I am running the stock airbox, stock ECU, a modified exhaust, and 31k on the clock. My Long Term Fuel Trims are in the postive 2-3 area and my short term fuel trims aren't that far off, either. They cycle like normal. Both LTFT banks are about equal.

I am thinking that it is one of a few things:

1. My MAF is going south (I am getting the P0172 - Too rich (Bank 1) fault code, but not as frequently). However, both LTFT banks are almost equal, so it would see as if both are affected?

2. Leaking injector in bank 2?

3. Vacuum hose not fully connected?

4. Oxygen sensor that reads the exhaust from bank two (I would assume that it is the right side?) is bad?

Any ideas? I am out of warranty, unfortunately, else I would just take it to Porsche. I have my own scan tool. Does the Porsche shop manual list any checks to perform when you get a P0175 (or P0172) OBDII code?

Thanks

 

Seems like if it was really running rich the fuel trims would be abnormal. Do the R and L wideband O2 sensors read about the same?

 

Well, they aren't wideband (unfortunately). One o2 sensor seems a bit slow (slightly), but I need to datalog it and analyze the graph in order to make sure.

My LTFTs typically sit around 0-1. They were at 2-3 today. Is that typical for my car? It was up a few points over what it normally is. However, both were, not just one (which makes me lean towards it being the MAF as that affects both vs an o2 sensor which would only affect one bank).

I am hoping that it is an o2 sensor or a dirty MAF (that can be cleaned).

 

Re cleaning the MAF, I have done it many times on my ESS 8 PSI S/C E39 540 as I have a K&N CAI filter, so the MAF does get some oil residue on it from time to time.

I use Simple Green, 50/50 , let just the element sit in the simple green for 5-10 minutes then completely rince off with cold running water. Then I use 99% IPA and rince it off again and then use a hair drier to blow off any excess IPA, it will evaporate very quickly anyway. Do not use the heat of the hair dries, just ambient air.

Works for me everytime and I have yet to replace my MAF...give it a try.

 

How long do you let it stay in the IPA?

 

P0175
Oxygen Sensing Adaptation, Idle Range, Bank 2 –
Below Limit
Diagnosis conditions
• Oxygen sensing system active
• Time elapsed after engine start-up: 250 to 350 seconds (USA)
• Time elapsed after engine start-up: 302 to 402 seconds (RoW)
• Engine temperature greater than 60 °C
Possible fault cause
♦ Incorrect signal from MAF sensor
♦ Fuel pressure too high
♦ Fuel injector leaking
♦ EVAP canister purge valve open
Affected terminals
-
Diagnosis/Troubleshooting
♦ If DTC P0445 (fuel tank vent valve - short to ground) is stored, correct this fault first. An open EVAP canister
purge valve can lead to the lean threshold being reached.
♦ For vehicles in the USA, the upper load range will probably not be reached. The only case in which a fault could
be stored is during driving while towing a trailer or caravan on a hill.
♦ Contrary adaptation values in connection with misfiring point to incorrectly adjusted control times
check control
times and adjust if necessary.
♦ If the fuel tank reserve light is switched on, no fault is entered.
Work instruction Display OK If not OK
1 Check signal from MAF
sensor.
♦ Connect special tool 9637.
♦ Measure voltage at pin III/23
and ground
♦ Switch on the ignition.
0.9 to 1.1 V. Replace MAF sensor
♦ Start the engine. Approx. 1.4 V
2 Check fuel pressure
Note!
DME 7.8 DME 7.8
2469 P0175 0-36.5 page 2
p0175
0
Printed in Germany – 6, 2002
3 Check fuel pressure regulator,
vacuum connection
and fuel return line
♦ Remove vacuum hose from fuel
pressure regulator
♦ Connect special tool 9103/2 to
vacuum hose
♦ Start the engine.
♦
0.4 - 0.6 bar Check the intake air
system for leaks
and check vacuum
line to fuel pressure
regulator for restrictions.
♦ Check housing of fuel pressure
regulator for damage and deformation
Replace the fuel
pressure regulator if
it is damaged with
the result that the
spring pre-tensioning
is increased
4 Check EVAP canister
purge valve
♦ Disconnect hose from EVAP canister
purge valve to intake system
at EVAP canister purge
valve
♦ Remove connector of EVAP canister
purge valve
♦ Connect special tool 9160/1 to
EVAP canister purge valve
♦ Generate vacuum of approx. 0.7
bar
The vacuum must
not fall below 0.5
bar after 10 minutes
5 Check fuel injectors for
leaks
Work instruction Display OK If not OK

 

I wonder is a loose/leaky gas cap would mimmic a leaking purge valve? Since the code is labeled " Oxygen Sensing Adaptation, Idle Range, Bank 2 – Below Limit" it sounds like the fuel trim would be trying to lean out the motor at a warm engine idle.

 

Here's something I found in a Ford TSB. Since everyone seems to have MAF failures that may be the place to start. You might just replace the MAF, If that doesn't correct the problem then you have a spare that you will need someday.

Article No. 98-23-10 MASS AIR FLOW (MAF) - SENSOR CONTAMINATION - SERVICE TIP

MASS AIR FLOW (MAF) DISCUSSION
MAF sensors can get contaminated from a variety of sources: dirt, oil, silicon, spider webs, potting compound from the sensor itself, etc. When a MAF sensor gets contaminated, it skews the transfer function such that the sensor over-estimates air flow at idle (causes the fuel system to go rich) and under-estimates air flow at high air flows (causes fuel system to go lean). This means Long Term Fuel Trims will learn lean (negative) corrections at idle and learn rich (positive) corrections at higher air flows.

If vehicle is driven at Wide Open Throttle (WOT) or high loads, the fuel system normally goes open loop rich to provide maximum power. If the MAF sensor is contaminated, the fuel system will actually be lean because of under-estimated air flow. During open loop fuel operation, the vehicle applies Long Term Fuel Trim corrections that have been learned during closed loop operation. These corrections are often lean corrections learned at lower air flows. This combination of under-estimated air flow and lean fuel trim corrections can result in spark knock/detonation and lack of power concerns at WOT and high loads.

One of the indicators for diagnosing this condition is barometric pressure. Barometric pressure (BARO) is inferred by the Powertrain Control Module (PCM) software at part throttle and WOT (there is no actual BARO sensor on MAF-equipped vehicles, except for the 3.8L Supercharged engine). At high air flows, a contaminated MAF sensor will under-estimate air flow coming into the engine, hence the PCM infers that the vehicle is operating at a higher altitude. The BARO reading is stored in Keep Alive Memory (KAM) after it is updated. Other indicators are Long Term Fuel Trim and MAF voltage at idle.

NOTE: THE FOLLOWING PROCEDURE MAY ALSO BE USED TO DIAGNOSE VEHICLES THAT DO NOT HAVE FUEL SYSTEM/HO2S SENSOR DTCs.



Symptoms
Lack of Power
Spark Knock/Detonation
Buck/Jerk
Hesitation/Surge on Acceleration
Malfunction Indicator Lamp (MIL) Illuminated - DTCs P0171, P0172, P0174, P0175 may be stored in memory
OBDII DTCs
P0171, P0174 (Fuel system lean, Bank 1 or 2)
P0172, P0175 (Fuel system rich, Bank 1 or 2)
P1130, P1131, P1132, (HO2S11 lack of switching, Bank 1)
P1150, P1151, P1152, (HO2S21 lack of switching, Bank 2)

 

ebaker, I first thought about it being the MAF. However, I am only getting the "right" bank faults. I have gotten that twice, now, in 10 days. If it was both the left and right, I would feel more confident in it being the MAF. I am leaning more towards an O2 sensor or leaking injector. Then again, my LTFTs (both left and right) seem to both be affected.

 

Couple of minutes Dock...its just to make sure there is no residue left from the Simple Green. How are things mate...any new stuff on your baby?

I am sure you saw my posts about the MPS2 and 04' GT2 wheels I bought, I am very happy with my setup. PSS9's next and the EVO kit once I sell my darn 540.

 

Since the problem is mild enough that it only trips a code every 10 days, it might be affecting both banks, but only happened to trip one bank.

 

True, in which case it would probably be the MAF. I still think that one of my o2 sensors is a bit lethargic, however.

 

I have a similer situation........however am fairly consistantly getting the 175 and 172 (both banks).....my car is significantly moded but last changes we made were 18 months ago.......and no codes til now.

I have OE MAF...........so, sounding like that would be worth a try?

 

If both are doing it, then the probability of it being the MAF seems more and more likely. I can't forsee that you have a leaking injector in each bank. Perhaps you have two bad o2 sensors, but chances are that you don't. A MAF issue typically causes both banks to issue the code.

 

Thanks.......I could have shared the rest of the story but didn't want to hijack the thread.

We did replace the bank 2 O2 sensor (ahead of cat) last month because we had a PO 155.
A few weeks passed and I got the 155 one more time.... along with a 172 & 175.
Several resets later and all I get now is 175 & 172 together (Porsche codes 360 & 361).