Check Engine Light P0171 Error
Senior Member
Joined: Mar 2021
Posts: 4,769
Likes: 2,379
Powering down the computer for just a minute will reset all tables and clear codes.
It causes the program to go into a full set of normal diagnostics when reconnected and first ignition on to start the motor.
If any function tested does not pass a CEL will be lighted and Code P1000 set.
If there is still an air leak, those code/s will come back depending o how fast the Long Term fuel tables shift during drive cycles.
The diagnostics above does not test this malfunction since it is a long term table that only shifts over time therefore could not be tested as a spot test.
There is one test that will take some time to complete because there are many part to it. That test is the Evap system involving the fuel tank closed system and may take a number of drive cycles. It has no relationship to the 171/174 codes you have been working on.
.
This is why a Scanner is needed to test and confirm all issues so you can see what conditions you have and any further service required.
Just reading codes only tells you a system condition exists, not the trouble or what to replace to fix it.
Good luck.
It causes the program to go into a full set of normal diagnostics when reconnected and first ignition on to start the motor.
If any function tested does not pass a CEL will be lighted and Code P1000 set.
If there is still an air leak, those code/s will come back depending o how fast the Long Term fuel tables shift during drive cycles.
The diagnostics above does not test this malfunction since it is a long term table that only shifts over time therefore could not be tested as a spot test.
There is one test that will take some time to complete because there are many part to it. That test is the Evap system involving the fuel tank closed system and may take a number of drive cycles. It has no relationship to the 171/174 codes you have been working on.
.
This is why a Scanner is needed to test and confirm all issues so you can see what conditions you have and any further service required.
Just reading codes only tells you a system condition exists, not the trouble or what to replace to fix it.
Good luck.
Junior Member
Joined: Sep 2021
Posts: 3
Likes: 0
Not sure if this problem has been fixed yet, but I had the same problem on my '02, 4.6L it was the PCV elbow on the back of the intake. dry and cracked making a vacuum leak
"dorman 46051 PCV elbow" on amazon fixed it, bit hard to change without a body lift...
"dorman 46051 PCV elbow" on amazon fixed it, bit hard to change without a body lift...
Thread Starter
5 Year Member
Joined: Aug 2019
Posts: 56
Likes: 60
Thanks for your input. I sold it but I let the new owner everything I could think of regarding the Check Engine light. He didn't seem to care He just wanted a hauler. He had a truck with a Check Engine light issue so he put a sticker over it. Done deal.
Junior Member
Joined: Nov 2025
Posts: 1
Likes: 0
0171 and no power
This indicates the fuel is running lean on bank 1. Will a bad exhaust manifold gasket cause this error? What is the common cause of this error?
When I get down to the nut cuttin' if the exhaust gasket caused the majority of P0171 errors, I won't fix it. I will probably bypass the Check Engine light and not worry about it. Anyone see a problem with this?
I bought this as a temporary truck while my Lightning is in the shop. It has 195,700+ miles on it and an abundant supply of rust. It only cost me $1,500. Replacing the gaskets would mean a lot of time fixing twisted off manifold bolts.
When I get down to the nut cuttin' if the exhaust gasket caused the majority of P0171 errors, I won't fix it. I will probably bypass the Check Engine light and not worry about it. Anyone see a problem with this?
I bought this as a temporary truck while my Lightning is in the shop. It has 195,700+ miles on it and an abundant supply of rust. It only cost me $1,500. Replacing the gaskets would mean a lot of time fixing twisted off manifold bolts.