Lean Faults and Fuel Trims (2005 VW Touareg 4.2L V8)

The methods in this video can be used when diagnosing fuel trim issues on any vehicle some of the format may be different between manufacturers.
In this video we are troubleshooting a 2005 Volkswagen Touareg with a 4.2L V8 engine, the customer complaint is a check engine light. There are lean faults stored and we are going to use fuel trims (I am using the factory scantool ODIS but you can use Generic OBD2 as well) and some experimenting to diagnose this vehicle. I hope you guys enjoy this video and thanks for watching.

[@ashleehill3786]

I very, very, rarely comment on anyone's videos, but I felt that I needed to Thank you for all the info you have made available thru your videos about fixing VWs. Well actually alot of the knowledge I have gained from you is troubleshooting and general testing procedures that can apply to any make or model which is even better!! I love how you ALWAYS explain and validate your findings, instead of saying what the problem is and how to fix it like most videos, you always go above and beyond to explain what brought you to the answer that fixed the problem... I've learned ALOT about VW watching your videos and just wanted to say Thanks and can't wait to learn more!!

[@halopersin]

Excellent video. I love how the methodic step by step problem solving you use in your electrical videos is used here. This just goes to show that whatever you’re diagnosing, the process is very similar.

[@EXOVCDS]

Got to love those plastic fittings! On the other hand... 13 years old, so I guess they lasted long enough. =)

[@VAYALAD10]

Here are my two favorite VW techs

[@dylankinch2735]

Good vid tommy. Your doing well with this you tube channel. You seem to get along with the camera pretty well. Thanks for taking the time to do this bro we all appreciate it.

[@PositiveLeadDiagnostics]

Thanks for the support Dylan

[@wyattoneable]

That was a great visual of O2 sensors adjusting fuel trims.

[@fieldsofomagh]

Very well diagnosed with fuel trims observations and easily understood.

[@shaunsautorepairs5410]

good repair...I don't think live data was needed for this but always good to see fuel trim data being used...thanks

[@haywardsautomotive6156]

No brake assist with DTC and lean codes and then hear the vacuum leak...you were probably smiling on this one. Good video Tom!

[@Diagnosedan]

Nice find Tom

[@OzMechanics]

Sweet video brother!!!

[@Flytieco]

Thanks for the video lots of help I've got this same issue.

[@ozzstars_cars]

Nice gravy there Tom ;-)

[@Pablo_Automotive]

Great job Tom 😉

[@victorvalderrama9058]

Good info ,very helpful🤔

[@roniacjourdan3085]

Hey thanks Positive , I learned from you today I have an 08 bar motor I had my valve covers done vehicle was fine took vehicle down to dealer for fuel pump gasket recall I get car back and vehicle now has p0174 ..is bank 2 drivers side bank 2 and I should be looking for vacuum leaks on hoses mainly on driver's side ? I had that brake booster vacuum hose leak in the past ..but which lambda sensors should I be watching for bank two

[@newcreationeconomics8398]

Hi, positive lead diagnostics! Nice job guys! My V8 TOUAREG RUNS AND STALLS. GUESS IT'S A FULL PUMP ISSUE. IS A VW V6 FUEL PUMP SAME AS A VW V8 FUEL PUMP?

[@Airman..]

You nailed it

[@ogalief]

Had the same issue with mine. With the vacuum leak, I got 8.5MPG city. Fixed it pretty damn quick! I do have one issue right now though. My 2005 V8 has the Kessy system, and all of the little black lock buttons on the door handles (except for the rear passenger door) aren't working. The all failed one-by-one over the past year. Can still unlock the doors though. Is this something that you've ever seen happen?

[@adaxu3300]

Hm, so the vacuum pump is also sucking it into the engine?..I thought it was separated from the engine vacuum and therefore not affecting it in any way..like, sucking it on the brake booster and releasing it into the atmosphere

[@bbkmm1]

Why is the O2 sensor voltage 1.54V? I thought they range from .1 to .9V? Or is this lambda sensors? at 2.4 or 3.2V?

[@Waldee84]

Hello Tom. Could you help me out with my Seat Toledo 2 (equivalent of Golf 4) 1.8 20V 125hp? I've P1128. Symptoms are: significant increase in fuel consumption, small misfires (not detected by VCDS), at steady cruising speed EGR is reading normal voltage but when gently stepping on gas pedal (not WOT) EGR is zeroing/closing. Duty cycle is 0%. At WOT, MAF reads only 60g/s (guess should be around 100g/s) and it's brand new. At higher RPM LTFT gets lean up to 20%. This would point to MAF, but again, it's new. Sometimes equivalence ratio goes down to 0.133. I don't think it's the fuel pump because LTFT goes up depending on my foot. It may never go up if I keep driving at lower RPM. And also lambda stays most of the time on rich side. Might be a false lean condition?

[@PositiveLeadDiagnostics]

Lack of power at wot? What are your o2 readings at wot?

[@Waldee84]

@@PositiveLeadDiagnostics A/F ratio is around 13 and equivalence is around 0.85. Cat was cut out so downstream gives inaccurate readings. Cat was replaced by previous owner and this one melted on me so I got rid of it until I fix this rich condition.

[@PositiveLeadDiagnostics]

I was thinking maybe a plugged exhaust. Any lack of power or is it just a check engine light?

[@PositiveLeadDiagnostics]

Is it an oem maf sensor?

[@Waldee84]

@@PositiveLeadDiagnostics Yes. Previous one was Bosch also. It was reading the same parameters as this one. I've destroyed it by trying to clean it.

[@allenk5649]

Nice to see the FT adjust live. Do you know how the VCDS compares to the factory scanner?

[@PositiveLeadDiagnostics]

It's similar but has a different format. You can also use expert mode with a snap on if you know the numbers

[@masterfastermasterfaster]

HOW BAD IS THIS SCANTOOL, it works with numbers !!!!

[@PositiveLeadDiagnostics]

If you use the guided functions tab you can look at the measured value descriptions instead of the numbers. The number can be confusing

[@5Dale65]

Got something similiar in VAG-COM.and VCDS. But I could load up a label file into the program, so all the mysterious numbers had been described. Perhaps you can do the same in your scantool?

[@grumpysgarage4790]

Nothing like heat aged plastic and rubber, especially German plastic and rubber. 😜

[@roadkill5333]

Seventeenth!!!

[@fernilu6998]

4th