Chain reaction in trouble codes?
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Give me coffee - Or beer!
Joined: Aug 2003
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From: Who cares?
Chain reaction in trouble codes?
I had the trouble codes set for the oxygen sensors. Let me clarify that. When my daughter went to get her truck inspected she was told that the trouble codes were set for the oxygen sensors. So I dutifully changed the two pre-cat sensors. Now the codes are set for "Bank 1 too lean" and "Bank 2 too lean." That is, code P0171 and P0174. 
I got this pulled by Autozone and the definition is in their system. They also list 4 or 5 other possibles for these codes including MAF sensor, ignition misfire-repair, fuel injector problem. These are on the P0171 code. The P0174 code lists MAF sensor, Failed H02s21, Ignition Misfire condition, Fuel injector problem and Engine Mechanical Condition. I gotta get this thing inspectable. Where do I go from here?
1999 F-150, 5.4 Ltr., V8 (Engine Code L), 90K + miles.
Thanks for the input.
I checked Haynes manual. The trouble codes list says "System Adaptive Fuel Too Lean" - Bank 1 and 2 respectively. A great help...NOT!
I got this pulled by Autozone and the definition is in their system. They also list 4 or 5 other possibles for these codes including MAF sensor, ignition misfire-repair, fuel injector problem. These are on the P0171 code. The P0174 code lists MAF sensor, Failed H02s21, Ignition Misfire condition, Fuel injector problem and Engine Mechanical Condition. I gotta get this thing inspectable. Where do I go from here?
1999 F-150, 5.4 Ltr., V8 (Engine Code L), 90K + miles.
Thanks for the input.
I checked Haynes manual. The trouble codes list says "System Adaptive Fuel Too Lean" - Bank 1 and 2 respectively. A great help...NOT!
Thread Starter
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Give me coffee - Or beer!
Joined: Aug 2003
Posts: 746
Likes: 7
From: Who cares?
As Steve said there are a lot of discussions on this topic. As I said there is nothing definitive. Time crunch cost me money. I changed the pre and post O2 sensors before I could get here and read the response. According to everything I read the trouble code itself should only be used to announce a problem somewhere and should not be a guide to a failed part. Apparently there are a good number of reasons for the code to be triggered. So start by troubleshooting the simplest (vacuum leak). I found a nearly severed piece of tubing going into the PCV. It was rotten and real soft. No codes yet, brand new O2 sensors, no other vacuum leaks, the truck should be good to go for another year. It seems to me that if there is going to be so many sensors on the vehicle why not a "Vacuum Leak" code that can tell the owner that all the other codes may be bogus? Oh well, live and learn, die and forget it all.
