Question about 2004 Chevrolet Impala

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2004 Chevy Impala SS 3.8L Supercharged: I am getting OBD2 codes P0171 (System too Lean (Bank 1)) and P0420 (Catalyst System Efficiency Below Threshold (Bank 1)). I also found an oil leak today. I replaced the O2 senor about 3 months ago. Any ideas?

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  • Chevrolet Master
  • 1,049 Answers

For p0171, try:
In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
Inspect all vacuum and PCV hoses, replace if necessary
Check for a dirty fuel filter and proper fuel pressure
for p0420, try:

Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.

Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).

Inspect the downstream heated oxygen sensor (HO2), replace if necessary

Replace the catalytic converter

Posted on Aug 23, 2011

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Posted on Jan 02, 2017

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06 Cadillac STS V8 car has codes P0174 and P0420.


• DTC P0171 Fuel Trim System Lean Bank 1
• DTC P0174 Fuel Trim System Lean Bank 2
.
The engine control module (ECM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during Open and Closed Loop. During Open Loop, the ECM determines fuel delivery based on sensor signals without oxygen sensor (O2S) input. During Closed Loop, the O2S inputs are added and used by the ECM to calculate short and long term fuel trim (FT) fuel delivery adjustments. If the O2S indicates a lean condition, FT values will be above 0 percent. If the O2S indicate a rich condition, FT values will be below 0 percent. Short term FT values change rapidly in response to the heated oxygen sensor (HO2S) voltage signals. Long term FT makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. If the ECM detects an excessively lean condition, DTC P0171 or P0174 sets.
Diagnostic Aids
• Excessive resistance in the fuel injector ignition 1 voltage circuit or the fuel injector control circuit may cause the following symptoms:
- Lean condition
- Misfire
- Rough idle
• The system will go lean if an injector is not suppling enough fuel.
• A lean condition could be present during high fuel demand.
• A malfunctioning MAF sensor can cause this DTC to set. Refer to DTC P0101 .
• Review the Failure Records with a scan. If an intermittent condition is suspected, refer to Intermittent Conditions .

DTC Descriptors
This diagnostic procedure supports the following DTCs:
• DTC P0420 Catalyst System Low Efficiency Bank 1
• DTC P0430 Catalyst System Low Efficiency Bank 2

This code could mean the catalytic converter on that bank has failed .

Causes of lean condition trouble codes P0171 P0174 GM 5 3L

P0420 P0430 catalytic converter catalyst inefficiency code diagnosis

Mar 28, 2018 | 2006 Cadillac STS

2 Answers

What means catalyst Efficiency below normal


      Got it scanned and it's P0420: Catalyst efficiency below thresholdbank 1. They said it could be a bad catalytic converter or oxygen sensor. I borrowed a scanner and tried to measure the oxygen sensor readings over time.Sep 8, 2011

      civic - Check Engine code P0420 Catalyst efficiency below ...

      mechanics.stackexchange.com/.../check-engine-code-p0420-catalyst-efficie...
    Feedback

    P0420 Error Code: Catalyst System Efficiency Below ...

    www.obd-codes.com/p0420
    P0420 OBD-II Trouble Code. Technical Description. Catalyst System Efficiency Below Threshold (Bank 1). What does that mean? This diagnostic trouble code ...

    P0420 Code Fix How Its Done Catalyst Efficiency Below ...

    ? 4:25
    https://www.youtube.com/watch?v=-c8090n1Ihs
    Jun 20, 2014 - Uploaded by ACE AUTOS UK
    Here is a tutorial on P0420 code fix catalyst efficiency below threshold How To Diagnose a p0420 code ...

Jan 26, 2016 | Cars & Trucks

1 Answer

Dakota p0171 p0174 taurus


code p0171 refers to system to lean bank 1==causes intake /exhaust leak--AIR system--MAP/MAF sensor--fuel pressure/pump--injectors--HO2s Have a fuel pressure test done on the fuel manifold to check for blocked filter/faulty pump/fuel pressure regulator faults
code p0174 refers to system to lean bank 2 --same causes including hose connection/s
code p0420 refers to catalytic converter system -bank 1 efficiency below threshold==causes catalytic converter--wiring--HO23. Check the cat converter is not cracked inside and the oxygen sensor is working.

Sep 06, 2013 | 2009 Citroen C8 2.0

1 Answer

I've had a trouble code( P0420) code come up,


Catalyst System Efficiency Below Threshold (Bank 1). OK, now tell me that again in plain English please.... let's break it down: the catalyst system being referred to is your three-way catalytic converter; so the catalytic converter is not working properly (i.e. it's not efficient). Bank 1 refers to the side of the engine which contains cylinder #1. On inline engines such as 4 & 5 cylinder engines, there is only one bank. So, to really simply things let's just say that the efficiency of the catalytic converter and/or exhaust pipe and/or O2 sensor is not so great. Hope this helps.

Mar 09, 2013 | Cars & Trucks

1 Answer

Bad catalytic converter on 2000 Monte Carlo SS


My son put his tester on it, gave him the code ??????? What code ? P0430 -P0420
P0430 Catalyst System Efficiency Below Threshold (Bank 2)

P0420 - Catalyst System Efficiency Below Threshold Bank 1

Sorry but you don't have a chance of doing this . special tools ,cost you you as much as to take to a shop . buying cheap cat's won't work either .

Oct 25, 2017 | Cars & Trucks

2 Answers

Engine light stays on, code is p0420 low thresh bank 1.... where is bank 1 located


I'm not sure you understand the difinition of OBD2 fault code P0420, it means that Catalytic converter in the exhaust that is connected to the engine cylinder bank that contains number one engine cylinder has fallen below the a allowed threshold of cleaning pollunts from the engines exhaust stream. I would be more specific but you have not given model or year of the Mercury you have.
Here is the full difinition of OBD2 fault code P0420 from the factory service information system.


P0420 - Catalyst System Efficiency Below Threshold (Bank 1)


Possible causes - Three way catalyst converter worn out
- Intake air leaks
- Fuel injectors may be faulty
- Fuel injector leaks
- Spark plugs may be faulty
- Improper ignition timing
- Engine Control Module

Jun 07, 2011 | Mercury Cougar Cars & Trucks

1 Answer

I am getting a P0420 code and a P0171 code on a 2000 Honda Passport 3.2 V6 What do I need to do to fix these? Car seems to drive fine and not in limp mode.


P0171 indicates a lean condition. The most common cause of this is a defective mass air flow sensor. Also check if any vacuum leaks.Replace MAf sensor,if cleaning the MAF does not help.

The code PO420 you have is Catalyst System efficiency is below threshold bank one. Usually replacing the O2 sensor that's the front most in the exhaust system will cure your problem,.



Thanks.

Sep 29, 2010 | 2000 Subaru Outback

1 Answer

Radiator fans fuses keep blowing-chevy impala 2002. we need info on following codes: P0108, P0128, P 0341, P 0401, P 0420, P 1480, and P 1481. John


p0108 map curcuit high input, p0128 coolant temperature below thermstat regulating tempurature, p0341 is camshaft position sensor A-bank 1 ckt range/performance, p0401 is exhaust gas recirculation, insufficiant flow detected, p0420 is catalyst system efficiency below threshold, p1480 is manufacturer control auxilary emission controls, p1481 is same as p1480.

Jun 15, 2010 | 2002 Chevrolet Impala

3 Answers

I had my car inspected and received P0420 code? what does it mean?


P0420 Error Code: Catalyst System Efficiency Below Threshold (Bank 1) Repair information for the OBD-II trouble code P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
www.obd-codes.com/p0420

Feb 18, 2010 | 2000 Toyota Celica

2 Answers

Check engine light on. P0325, P0420 2000 Subaru


CODE PO420 CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD BANK I * CODE PO325 KNOCK SENSOR NO.1 CIRCUIT MALFUNCTION BANK NO.1 OR SINGLE SENSOR

Nov 13, 2009 | 2000 Subaru Outback

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