Recurring Check engine light
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Recurring Check engine light
HELP!!
I have a check engine light that seems to not go away for long.
Changed o2 sensors ,mapsensor , had intake manifold gasket changed . Now they want to change throttle body. For a tune of $650.
Any knowledgeable ,trustworthy mechanics in Olympia ,Wa.
I have a check engine light that seems to not go away for long.
Changed o2 sensors ,mapsensor , had intake manifold gasket changed . Now they want to change throttle body. For a tune of $650.
Any knowledgeable ,trustworthy mechanics in Olympia ,Wa.
Senior Member
Joined: Jul 2004
Posts: 6,200
Likes: 39
From: Easton, Pa.
From your description, your shop has no idea what they are doing, but guessing and costing you money.
The codes are for two different issues at the same time.
Code 171 is bank 1 fuel table shifted rich.
The problem needs to be looked at with a SCANNER to see if bank 2 is also shifted as well because it indicates what the next part of diagnostics is needed.
If no bank 2 shift beyond 10%, bank one Ox sensor is detecting to much oxygen in the exhaust. It's NOT the sensor, do not change it.
Set about determine the source of the intake vacuum leak and make the repair..
.
The 300 code is random misfires detected.
Again the ignition misfire counts need to be looked with a SCANNER at to ID one or more cylinders, then is it plugs, is it coils, is it plug wires.
Until you get a shop that understands these things, stop with the shop you now have.
Code are the indicator to start at, not the point to guess from..
Good luck.
The codes are for two different issues at the same time.
Code 171 is bank 1 fuel table shifted rich.
The problem needs to be looked at with a SCANNER to see if bank 2 is also shifted as well because it indicates what the next part of diagnostics is needed.
If no bank 2 shift beyond 10%, bank one Ox sensor is detecting to much oxygen in the exhaust. It's NOT the sensor, do not change it.
Set about determine the source of the intake vacuum leak and make the repair..
.
The 300 code is random misfires detected.
Again the ignition misfire counts need to be looked with a SCANNER at to ID one or more cylinders, then is it plugs, is it coils, is it plug wires.
Until you get a shop that understands these things, stop with the shop you now have.
Code are the indicator to start at, not the point to guess from..
Good luck.
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Senior Member
Joined: Dec 2006
Posts: 43,542
Likes: 819
From: Joplin MO
I've bolded common causes of the P0133 and P0171:
A code P0133 may mean that one or more of the following has happened:
The oxygen sensor is faulty (Bank 1 Sensor 1)
The wiring to the sensor is broken / frayed
There is an exhaust leak
A code P0171 may mean that one or more of the following has happened:
The MAF (Mass Air Flow) Sensor is dirty or faulty Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
There could be a vacuum leak downstream of the MAF sensor
Possible cracked vacuum or PCV line/connection
Faulty or stuck open PCV valve
Failed or faulty oxygen sensor (bank 1, sensor 1)
Sticking/plugged or failed fuel injector
Low fuel pressure (possible plugged/dirty fuel filter!)
Exhaust leak between engine and first oxygen sensor
A code P0133 may mean that one or more of the following has happened:
The oxygen sensor is faulty (Bank 1 Sensor 1)
The wiring to the sensor is broken / frayed
There is an exhaust leak
A code P0171 may mean that one or more of the following has happened:
The MAF (Mass Air Flow) Sensor is dirty or faulty Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
There could be a vacuum leak downstream of the MAF sensor
Possible cracked vacuum or PCV line/connection
Faulty or stuck open PCV valve
Failed or faulty oxygen sensor (bank 1, sensor 1)
Sticking/plugged or failed fuel injector
Low fuel pressure (possible plugged/dirty fuel filter!)
Exhaust leak between engine and first oxygen sensor