AZSantorin

16555 - Fuel Trim: System Too Lean: Bank 1
P0171 - 92-00 - Unknown Error Elaboration
16558 - Fuel Trim: System Too Lean: Bank 2
P0174 - 93-00 - Unknown Error Elaboration

'97 Cab returned from the shop for routine maintenance and diagnostics to check these codes. I replaced the 2 front 02 sensors and 2 vac hoses.

The car's been driving fine for about 2 weeks (before, the CEL came on within days), but the CEL came on again today with the same codes. The mechanic had told me the MAF readings were nearing a 20% threshold... but unfortunately, I didn't know what values he was talking about.

Today, I performed the MAF voltage test in the Bentley. The prescribed voltage for the MAF at idle is between .3 and 1.1 volts.... I was reading 1.4 volts. At RPM's up to 4000, The range was ok. 1.4 to about 2.7. The specified values are 1.5 min to 3.4 Max.

From that data, it seems a new MAF is in order. There are several other potential sources for these codes including an FPR (which is likely out of my league to test).

Any ideas? TIA!

MikTip

You have the Bentley? Those codes not listed in the Bentley?

AZSantorin

Just wonderin' if anyone had BTDT with this type of problem.

MikTip

Also try and get a "used" MAF sensor to verify the problem.

On www.car-parts.com there are dozens of Audi V6 engine parts available. I often buy complete MAF's with sensor, for less than $50, and they function fine! ;o)

If you like, I can send you one of my MAF sensor's
for testing? Throw me the part number off your current one for verification! ;O)

AZSantorin

Yeah, the same codes before the O2 replacements, but it took longer for them to come on this time after reset.

I just ordered a new MAF from thepartsbin.com for $440!! :-O
The lowest cost used one on that site you sent (thanks) was $275. I'm concerned about getting a used one as this one wore out after only 60k :-/

P/N (I think) is 078 188 471A
It's a Hitachi unit that has the these two numbers on it as well
I 2/13/97
PBT CF40

Got anything similar around?

MikTip

From the car-parts.com site-

1995
Air Flow Meter
Audi Series 90 AWD,FI,2.8L 010602 $125 Beltsville Auto Recyclers USA-MD(Beltsville) E-mail 1-800-249-1681
1995
Air Flow Meter
Audi Series 90 NEED NUMBERS B1224 $125 America II Inc. USA-NJ(Mays-Landing) E-mail 1-866-883-4799
1995
Air Flow Meter
Audi Series 80/90 90- J079 $100 Aace Auto Salvage USA-NC(Shelby) E-mail 1-800-247-9505
1995
Air Flow Meter
Audi Series 90 [336-59873] (STORE:4) CVK416C $100 Garry's Crestview - Greenleaf USA-FL(Crestview) E-mail 1-800-747-1888
1995
Air Flow Meter
Audi Series 90 70281 $100 Santa Fe Auto Salvage USA-CA(Riverside-Co) E-mail 1-877-687-9273
1995
Air Flow Meter
Audi Series 90 00000433 $100 Grand Valley Auto Parts USA-MI(Jennison) E-mail 1-800-457-0227
1995
Air Flow Meter
Audi Series 80/90 90- RC H3918 $75 Jack's Used Cars and Parts USA-MA(North-Billerica) E-mail 1-888-873-5225
1995
Air Flow Meter
Audi Series 90 C130 $75 Mitchell Auto Salvage USA-TN(Fayetteville) E-mail 1-888-433-0050
1995
Air Flow Meter
Audi Series 90 078 133 471A,AFH70-08B P20039 $75 Silvers Auto Parts USA-ME(Orono) E-mail 1-888-666-2124
1995
Air Flow Meter
Audi Series 90 T 011648 $74.61 Southern Tier Auto Recycling USA-NY(Beaver-Dams) E-mail 1-800-640-7995
1995
Air Flow Meter
Audi Series 80/90 90- U 008325 $65 Dumbleton Used Auto Parts, Inc. USA-NY(Pavilion) E-mail 1-800-634-7964
1995
Air Flow Meter
Audi Series 90 C157 $65 Pam's Auto USA-MN(St-Cloud) E-mail 1-800-560-7336
1995
Air Flow Meter
Audi Series 90 078133471 AFH70-08A 0E0257 $60 Toms Foreign Auto Parts - QRP Partner USA-CT(Waterbury) E-mail 1-800-255-6656
1995
Air Flow Meter
Audi Series 90 078133471A,AFH7008B, I54394,4D,SD,QUT 9F0277 $60 Toms Foreign Auto Parts - QRP Partner USA-CT(Waterbury) E-mail 1-800-255-6656
1995
Air Flow Meter
Audi Series 90 1 YEAR WARRANTY 078133471AFH70 X289 $58 Borges Foreign Auto USA-MA(Dighton) Quote 1-800-662-6150 Insurance-Quote
1995
Air Flow Meter
Audi Series 90 1 YEAR WARRANTY Y113 $58 Borges Foreign Auto USA-MA(Dighton) Quote 1-800-662-6150 Insurance-Quote
1995
Air Flow Meter
Audi Series 90 078 133 471a CD23 $55 General Auto Recycling USA-RI(Tiverton) E-mail 1-800-556-7316

Ya might want to remove the MAF sensor, and take a close look at the heated wire elements. They might need cleaning? ;O)

AZSantorin

Thanks for the info. I'll clean it out and see. What is the process? I've read from others that carb cleaner will do work okay. Why such the difference in prices for the same part??

JaXeN

Lots of detailed posts regarding this.

MikTip

Audi's sell differently in different regions of the country. In the Northern states, they often command "Top Dollar". In the Southern states, they dont sell well. Same goes for used parts. Certain parts sell better than others, plus depending on the salvage yard, and its location, prices will vary.

AZSantorin

Bought some electrical contact cleaner from Radio Shack and gently cleaned the two contacts inside.

/me crosses fingers