OBD Lean bank codes

[proradvlx]

Has anyone had this problem before: Got a Service Engine light, ran the code, and showed "Left engine bank lean" code. So replaced the left and right O2 sensors. Cleared the code out of the system, and it ran fine..... for a while. About week later, got another code - "Left engine bank lean" code again - thought the system was still learning that the O2 sensor had been replaced - cleared code. About ten days later, engine light - "Right engine bank lean" code.

But, what I have noticed is that this code, either left or right bank problem, only happens when the vehicle has been left idiling, after driving for a while. Does not happen on initial start up/warm up.

If I get to my destination, and park and shut the vehicle off, no problem - just when it sits idiling, that is when it seems to throw that engine code.

So - anyone ever had that problem before? And, how did you end up fixing it!!!

Thanks for the information.

Brent
2004 XLT AWD 4.0Flex 4Dr.

 

[swetrid]

Ford has tsb for this concern.
Printable View (6 KB)
TSB
04-22-11 MALFUNCTION INDICATOR LAMP (MIL) ILLUMINATED WITH DIAGNOSTIC TROUBLE CODES (DTC'S) P0172, P0175, P0171 AND/OR P0174 - 4.0L SOHC ENGINE - VEHICLES BUILT PRIOR TO 10/4/2004

Publication Date: October 28, 2004

FORD: 2004-2005 Explorer
MERCURY: 2004-2005 Mountaineer


This article supersedes TSB 04-19-7 to update the vehicle model years and DTC information.

ISSUE:
Some 2004-2005 Explorer 4dr/Mountaineer vehicles built prior to 10/4/2004 with the 4.0L SOHC engine, may exhibit the MIL illuminated with one or more of the following DTC's:

P0172 - SYSTEM TOO RICH (BANK 1)
P0175 - SYSTEM TOO RICH (BANK 2)
P0171 - SYSTEM TOO LEAN (BANK 1)
P0174 - SYSTEM TOO LEAN (BANK 2)

ACTION:
Reprogram the powertrain control module (PCM) to the latest calibration using WDS release B33.10 or higher. Calibration files may also be obtained at www.motorcraft.com.


WARRANTY STATUS:
Eligible Under Provisions Of New Vehicle Limited Warranty Coverage And Emissions Warranty Coverage

OPERATION DESCRIPTION TIME
042211A Check For Diagnostic Trouble Codes And Reprogram Powertain Control Module 0.4 Hr.

DEALER CODING
BASIC PART NO. CONDITION CODE
RECALEM 04

--------------------------------------------------------------------------------

NOTE: The information in Technical Service Bulletins is intended for use by trained, professional technicians with the knowledge, tools, and equipment to do the job properly and safely. It informs these technicians of conditions that may occur on some vehicles, or provides information that could assist in proper vehicle service. The procedures should not be performed by "do-it-yourselfers". Do not assume that a condition described affects your car or truck. Contact a Ford, Lincoln, or Mercury dealership to determine whether the Bulletin applies to your vehicle. Warranty Policy and Extended Service Plan documentation determine Warranty and/or Extended Service Plan coverage unless stated otherwise in the TSB article. The information in this Technical Service Bulletin (TSB) was current at the time of printing. Ford Motor Company reserves the right to supercede this information with updates. The most recent information is available through Ford Motor Company's on-line technical resources.

Copyright © 2004 Ford Motor Company

 

[gm558]

Has anyone had this problem before: Got a Service Engine light, ran the code, and showed "Left engine bank lean" code. So replaced the left and right O2 sensors. Cleared the code out of the system, and it ran fine..... for a while. About week later, got another code - "Left engine bank lean" code again - thought the system was still learning that the O2 sensor had been replaced - cleared code. About ten days later, engine light - "Right engine bank lean" code.

But, what I have noticed is that this code, either left or right bank problem, only happens when the vehicle has been left idiling, after driving for a while. Does not happen on initial start up/warm up.

If I get to my destination, and park and shut the vehicle off, no problem - just when it sits idiling, that is when it seems to throw that engine code.

So - anyone ever had that problem before? And, how did you end up fixing it!!!

Thanks for the information.

Brent
2004 XLT AWD 4.0Flex 4Dr.

Sounds like a possible vacuum leak. Check your lines, especially PCV lines.

 

[tmaher]

i had the same lean codes on my '03 explorer. there is a thread somewhere here that describes the cause of the problem. If you take the cover off your engine you will see a 90 degree hose that i think is part of the emissions system. It should show signs of wear and cracking. replace it. i got a replacement radiator hose similar in I.D. and cut to fit. search this site for the 171 and 174 codes and you'll find your solution.

 

[swshawaii]

This?

http://www.explorerforum.com/forums/showthread.php?t=314670

 

[tmaher]

Yep. that's the bugger. replace it, clear the codes and happy motoring!!!

 

[Bobbylew]

Has anyone had this problem before: Got a Service Engine light, ran the code, and showed "Left engine bank lean" code. So replaced the left and right O2 sensors. Cleared the code out of the system, and it ran fine..... for a while. About week later, got another code - "Left engine bank lean" code again - thought the system was still learning that the O2 sensor had been replaced - cleared code. About ten days later, engine light - "Right engine bank lean" code.

But, what I have noticed is that this code, either left or right bank problem, only happens when the vehicle has been left idiling, after driving for a while. Does not happen on initial start up/warm up.

If I get to my destination, and park and shut the vehicle off, no problem - just when it sits idiling, that is when it seems to throw that engine code.

So - anyone ever had that problem before? And, how did you end up fixing it!!!

Thanks for the information.

Brent
2004 XLT AWD 4.0Flex 4Dr.

Well, I have a 2004 Explorer XLS that sat for over 2 years, due to the guy's losing all his PATS Keys. He didn't want to mess with it, so almost gave it to me. I installed a bench programmed PCM with two uncut, PATS- Coded keys and it started an ran after getting them cut. Now, the DTCs are Bank #1 too rich and Bank #2 too lean! It's really weird that one bank would be rich and the other lean when they're fed by the same manifold. Not Injector Faults found, either. I have found a couple of vacuum leaks and have new Oxygen Sensors on the way, a new PCV Valve, Hose and MAF Sensor. I may install the new MAF Sensor and have already installed new Intake Manifold O-ring seals. This has become a "Shotgun Job"!

Hope you had good luck with yours!