Chevy Impala, check engine light on

Joined
Jun 12, 2012
Messages
214
Likes
5
Points
18
#1
Make
chevy
Model
impala
Year
2003
Miles
117,731
Engine
V6
2003 impala. check engine light just came on. Local auto store put the 'puter on it and it said : Fault is P0171, something like bank 1 running lean. Their cheapy reader didn't elaborate as to what part is bad. Can anyone shed some light on this?
 

grcauto

Hero Member
Joined
May 29, 2014
Messages
610
Likes
38
Points
28
#2
Bank one is lean. Exhaust leak prior to the cat?
 
Joined
Aug 27, 2019
Messages
12
Likes
0
Points
1
#3
No way to tell what part is bad without actual diagnostic work. The code gives you a starting point only. Could be a bad O2 stuck low, or if actually a lean condition it could be a leak anywhere between the MAF and the intake port(s). If nothing is obviously broken/cracked/disconnected from a visual inspection under the hood, the quickest way to identify that would be a smoke test--recommend you take the car to a shop if you don't have a way to verify fuel trims.
 

nickb2

Wrench. Diagnostic Tech.
Joined
Nov 22, 2008
Messages
9,925
Likes
180
Points
63
Location
St-Hyacinthe, Quebec, Canada
#4
Here are a few hints.

If it would have coded both banks, we would lean, pun intended, towards a fuel "deprived" system strategy, such as a intake boot leak, weak fuel pump etc. But since it is coding only on one bank, look for a vac leak at intake gasket for that bank or an exhaust leak on that side(bank). .
 
Last edited:
Joined
Aug 28, 2007
Messages
4,794
Likes
26
Points
48
#5
Guys trying to sell me auto warranty, tell me a check engine light on can cost me thousands of dollars.

Lean can mean one of two things, excess air or a deficiency of fuel, kid had a Pontiac close to your year, remember when Pontiac's use to be Pontiac's and Chevy's were Chevy's, now you can't tell the difference between a Chevy or a Cadillac.

His problem was a bad gasket for the manifold pressure sensor one look under the hood, could hear it suck air. Had a tube of Permatex gasket maker, squeezed that around the sensor, reset the code and saved thousands of dollars.
 

nickb2

Wrench. Diagnostic Tech.
Joined
Nov 22, 2008
Messages
9,925
Likes
180
Points
63
Location
St-Hyacinthe, Quebec, Canada
#6
His problem was a bad gasket for the manifold pressure sensor one look under the hood, could hear it suck air. Had a tube of Permatex gasket maker, squeezed that around the sensor, reset the code and saved thousands of dollars.
I put that shyte on everything. :beer::beer:


 
Joined
Aug 28, 2007
Messages
4,794
Likes
26
Points
48
#7
Ha, if shyt works why not? Only way to get a new gasket was to buy a new manifold pressure gauge.

Another friend paid $1,500.00 to a shop with the same code and rough running engine, replaced this and that, but didn't cure the problem. His was loose intake manifold bolts, two minutes later problem went away.

This is another common problem with this engine.


Plastic intake manifold, not bad on a straight four or six, but has a different coefficient of expansion than cast iron or aluminum so develops cracks squeezed in between two heads.

Never was a problem when the entire engine was cast iron, claim they are saving weight, many people have more on their gut than the weight that is saved, key reason for these changes, a heck of a lot cheaper to manufacture, but sure can't tell this from the replacement cost. 700 degree F as opposed to 2,500 and no machining afterwards.

As an engineer have to do what the bean counters want or you won't have a job.