P0171 Trouble Code: System Too Lean Bank 1 Diagnosis

In this video, I show you how I troubleshoot a Check Engine Light (CEL) / Diagnostic Trouble Code (DTC) P0171, System Too Lean Bank 1. The exact vehicle in video is a 2002 Toyota Tacoma standard cab 4 cylinder pickup truck. The techniques shown can be used on many vehicles, not just Toyotas.

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Due to factors beyond the control of the Big Dog50001 Automotive Channel, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. The Big Dog50001 Automotive Channel assumes no liability for property damage or injury incurred as a result of any of the information contained in this video.

The Big Dog50001 Automotive Channel recommends safe practices when working with power tools, in on or around automobiles or other vehicles, automotive lifts, lifting tools, jack stands, electrical equipment, automotive modules and systems, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video.

Due to factors beyond the control of the Big Dog50001 Automotive Channel, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not the Big Dog50001 Automotive Channel.

[TheBigOPossum]

One of the BEST diagnostic and troubleshooting videos I have ever seen. Thouroughly and easy to understand explanation of potential problems, causes and fixes for the P1071 code. BRAVO!!! At 77 years of age and very much an old school mechanic, I have been trying to self educate myself on the more modern engine design and theory. Your video is JUST WHAT this old guy needed. THANK you so much.

[msvirtual]

It would be impossible to add up all the hours of auto repair videos I've watched over the last 8-10 years. THIS ONE, though, MAN!! In only 46 mins... I'm speechless at how easily I absorbed every concept and it made logical sense. I was starting to diagnose ahead of you! You sir, not only have a gift of mechanics and troubleshooting, you have an even greater gift of TEACHER. Never boring, just a concise step-by-step stream of logical information. I stood at a standing ovation at the end of this video, and I cannot thank you enough for the education you imparted upon me. Thanks Dawg!

[calkoho]

hard to overstate how sharp this guy is. Beautiful explanation . This is at a high level expert mechanic level!

[stupagia]

i don't normally respond to videos, but I almost felt like this gentleman was standing next to me and showing me all this in person and not shouting at me. Best of all is I appreciated how he explained everything he was looking at and what significance it had in terms I could easily follow along with. Turns out he lives in my neck o' the woods. Thanks Big Dog! I promise I won't tell, Scotty! :{>

[tonyfox]

I watch and learn diagnostic trouble codes daily and to be honest, your way of using a cheap code reader with live data was the most interesting and informative video I have seen in a long time. Thank you, and all on a cheap device !!

[robertlardon]

The most thorough and insightful "how-to diagnostic" car video I've seen! The 46 mins went fast with no fluff; just great information. Big Dog is a great mechanic and teacher!

[SAMBITAR-wo]

THE MOST DETAIL DIAGNOSTICS PROCEDURE PRESENTED IN THIS CASE STUDY. SO BENIFICAL AND ACCURATE. THROUGH DIAGNOSTICS
1) VACUUM LEAK 2) BAD MAF 3) BAD BRAKE BOOSTER.
ALL 3 STEPS ARE SUPPOERTED WITH STFT AND LTFT.
JUST PERFECT WORK.

[michaelclayton]

As a driveability expert myself, you did an absolute awesome job, for not only a layman, but also experienced technicians! I am not ashamed to say I picked up a few tips too! Outstanding!

[ericjernigan]

Hands down the best diagnostic video I've ever watched on Youtube (and I've watched a ton). I learned more in that 46 minute video than all the others combined. Outstanding teaching video.

[SDMev]

Some of the best 46 minutes I’ve ever spent.

[netwonc]

The very best analysis of this problem. Shows how to test all systems. Thanks for sharing your knowledge with us.

[darrinfaulkner]

I sat and watch this whole video on my 1 hour lunch break and must say this mechanic is like a school teacher that was teaching myself the student.Great video and he was very articulate and professional in narrowing down the problem.The explaining of the OB2 reader was on point as well because I use mines alot but dont understand some of the word play on the tool until you explained it.Thumbs up to your video👍...

[erobbinstube]

I came here trying to track down a P0171 code on a 2003 Toyota Corolla, and while I think my problem is due to a leak at the intake manifold, I was floored by the quality of this video. I work in the high tech field and work on troubleshooting issues on a daily basis. This video is a text book example of the method needed to properly come to understand the root issue of a problem. Outstanding video.

[boriszhang]

I want to thank you for posting this very detailed diagnosis video. I have a 06 Accord with a pending CEL code P0171. Fuel trim was at +25% at warm idle. I followed your procedure, and found out that my air intake tube had 2 huge cracks. After installing the new tube, fuel trim wasn’t changed. I moved on to see the live data and found out my MAF sensor was under reporting. Since the Tacoma in your video and my Accord all have the same size engine, 2.4L, I found my MAF was under reporting even worse than the Tacoma in this video. I ordered a new MAF sensor and now the problem is solved! Thank you again sir as p0171 can be very tricky and costly to diagnose. Your video is extremely helpful and saved me a lot of money. As a DIYer myself, these videos really help!

[spiketaterman]

Thanks for this! Was driving my car over rough roads, and the check engine light came on. It threw a P0171 code. Once home, I popped the hood and saw this plastic chamber thing had fallen off the air intake throat pipe DOWNSTREAM from the MAF sensor. Popped it back on and tightened clamp with a screwdriver and good to go! I love youtube university...

[candicekillmer]

This video helped more than any other video I've watched trying to figure out how to fix the p0171 code. And I'll be dammed if it isn't a freaking brake booster leak. We have Been trying to find this vacuum leak for 3 months and couldn't find anything. Replaced many parts trying to fix /find the vacuum leak. A lot of money into repairs that weren't needed and a waste of money. Thank you for going through every possible reason to get this code. This car was pissing me off and I've become more of a mechanic than I ever wanted to be. You just saved my scion tc from going to the scrap yard. Thank you!

[rubbermalet]

this is actually "prime time info" bro
im a retired mechanic with many years in the industry - i still practice with neigbs & friends' cars lol- and the way you'd explain everything regarding this issue is basically the same way automobile instructors do at automechanic schools & at college level too, very professionaly w/o any gimicks

thank you for taking this time and to help us to understand the technicalities involved within 💖

[stealthginfiniti]

Thank you very much for helping fix my car. First it started with a P0420 Catalytic efficiency code. Then graduated to a P0171 lean code. Your method of explaining Fuel Trims issues and MAF Sensor testing was the Key to determining a vacuum leak. Then I looked at all hoses and used Brake Cleaner still couldn't find the leak. Finally after a quick prayer, I remembered, don't forget the brake Booster and PVC valve. Sure enough, I pinched the PVC hose to the intake manifold and the short trim fuel went from Maximum to Zero in bank 2. Bank 1 went from Maximum to about 3. Tomorrow I'm installing a new PVC valve.

[billlincoln]

THE BEST MAF DIAGNOSTICS ON THE INTERNET.

[alia]

This was an EXCELLENT video, good job Dave. You're a good speaker and a camera operator. You dumbed down how an ECU manages the engine to a level that I think most of us will grasp easily. Your steps are logical and easy to follow. Thanks for taking the time to make this video.