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Error code P0300 P0420 - Hummer Cars & Trucks

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6 Suggested Answers

6ya6ya
  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

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Posted on Jan 02, 2017

  • 66 Answers

SOURCE: 12 codes; 90174, p0171, p0175,p0300,p0301, p0302,

I would be very hesitant about just going in and replacing parts/sensors, especially those diagnosed from Electronic Control Module (ECM) Diagnostic Trouble codes (DTC's) alone, as quite often when multiple codes are present, they are often related to a songle malfunction/failure (Such as coil codes, and O2, rich/lean codes, etc...) - A p0171 and 0174 code is not indicative of a faulty MAF sensor - it is a code set when a lean condition is detected within the vehicle's exhaust...often caused by vacuum leaks, EGR valve malfunctions, BAC/IAC ( Bypass/Idle air control) valve malfunction, DPFE sensor malfunction, or the MAF "hot wire" is dirty, and can be cleaned with the correct cleaner, but instead of replacing a $250 MAF sensor; only to later find out that if you had the vehicle repaired by a trained technician, a $3 vacuum hose and a $50 ignition coil had initiated the multiple DTC's - So, sometimes it does pay to use a trained technician; especially with so many codes present - Like I said - If I were going to do the work myself, I would erase all the codes (Disconnect battery cable for about 10 mins - this will also erase the block/learn ECM settings and it may search for idle for a bit, but will straighten out with time - reconnect battery and start the car - then after the light re-illuminates, re-pull the codes, and most importantly test the sensors/parts indicated by the DTC's before replacing anything - that is if you want to fix it the most cost effective way possible, but, if you have plenty of money to waste you could always just go replace whatever the DTC's tell you is out of specifications, regardless of the cause...this might fix it, but may not as well - if you got lots of money and feel lucky it's the way to go - if not, test those parts and sensor before replacing them - there is a process for testing each of them....Thanks

Posted on Aug 22, 2009

Testimonial: "Thanks you so very much. The car was shaking and making a knocking sound and running very poorly and now the engine is locked I had in towed home."

wracefans24
  • 1985 Answers

SOURCE: 5 error cods on my 2002 Jetta GLS 1.8 Turbo Engine

P0420= Catalyst System Efficiency Below Threshold Bank 1
P0300=Random/Multiple Cylinder Misfire Detected
P0301=Cylinder 1 Misfire Detected
P0172=System Too Rich Bank 1
P2181=Cooling System Performance
you need to write these down,have someone clear the codes in the car,then go for short ride and recheck which if any code reappears.it's like domino's affect,one sensor can start a chain affect with the others.

Posted on Dec 10, 2009

  • 216 Answers

SOURCE: my 2005 pontiac grand prix has a bad misfire and

you have a cracked vaccum hose going to your fuel regulator and purge valve.

Posted on Jan 01, 2011

jturcotte
  • 7779 Answers

SOURCE: my 2002 nissan primera has

Hi, you may be running rich. Not sure which engine you have, and this car is not sold in the US, but if you have a vacuum operated fuel pressure regulator on the fuel rail, check it for a torn diaphram. See #2 at the following post: http://www.fixya.com/cars/r7427423-fix_poor_idle_high_idle_stalling_fuel

Posted on Jan 19, 2011

  • 79 Answers

SOURCE: 2004 lincoln ls codes

p0300 is a random engine misfire and p0420 is catalytic converter efficieny below threshhold bank1. one easily causes the other. only way to be sure you get it fixed would be a tune up, new cat converter and o2 sensors

Posted on Aug 10, 2012

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Codes po303, po171, po137. po420


2000 Toyota Corolla, P0171 & P0420 codes - YouTube

? 5:43
https://www.youtube.com/watch?v=ahJnJ19-vwY
Jun 13, 2011 - Uploaded by StandardBrandParts
Standard Motor Products presents: Technician's Toolbox "2000Toyota Corolla, P0171 & P0420 codes"

Smoke testing for codes P0171 P0174 - YouTube

? 5:48
https://www.youtube.com/watch?v=kZsqEfP-5zM
Jan 18, 2011 - Uploaded by realfixesrealfast
These two codes mean a V style engine is running lean on both banks. So you have to be thinking - what can ...

How to repair fault code P0171 and reset warning light ...

? 26:31
https://www.youtube.com/watch?v=Y8FBGrCT3rM
Nov 27, 2014 - Uploaded by Peter Finn
How to repair and fix fault or error code P0171 and reset warning light Toyota Corolla VVT-i engine. ... Also how to find fault codeusing OBD scanner. ... Trouble shooting a misfire, Code P0300, P0301, P0302, P0303, P0304, P0305, P0306, ... 2000 Toyota Corolla, P0171 & P0420 codes - Duration: 5:43. by ...


Dec 02, 2015 | 2005 Toyota Corolla

1 Answer

Dose this mean computer die?wont start new fuelpump so where do i go from here ? new computer or what


Take it to a ASE certified repair facility ,they'll fix it up ! Don't just replace parts !!!!!

P0171 - is a lean code bank 1 -possible vacuum leak , low fuel pressure , plugged fuel filter ,
P0300 - is a random misfire code which is understandable with a lean code .
P0420 As the code description implies the P0420 code means that the vehicle's control module has detected that the three-way catalytic converter is not working properly (is not as efficient as the factory is expecting). Replacing the oxygen (O2) sensors may sometimes fix the code, but in most cases the catalytic convert needs to be replaced to fix the problem. If the P0420 code is combined with other codes, try fixing the other codes first
P0452 - EVAP Control System Pressure Sensor Low Input
P0446 - Evaporative Emission Vent System Performance
P0453 - Fuel Tank Pressure Sensor Circuit High Voltage
P1639 - PCM 5 Volt Reference Voltage Circuit Condition
P1653 - Power Steering Output Circuit Malfunction
P1651 - Fan 1 Relay Control Circuit
If you don't know what your doing take it to a repair shop before you waste your money ! You have a lot of problems here an I don't think the computer is bad , I'd say lack of maintenance ! You need to learn how to test thing's to fix them ! From the five volt reference voltage code , I'd say one of your sensors is shorted internally bring down the ref. voltage circuit causing the no start, but then again the 5volt ref. circuit in the PCM could be the problem . What you need to do is Disconnect all sensors that receive 5volt ref. signal one at a time an see if it will start . If I knew what year vehicle yours is I could tell you what sensors ! MAP, TPS , etc...










Jul 06, 2015 | Oldsmobile Silhouette Cars & Trucks

1 Answer

2004 lincoln ls codes


p0300 is a random engine misfire and p0420 is catalytic converter efficieny below threshhold bank1. one easily causes the other. only way to be sure you get it fixed would be a tune up, new cat converter and o2 sensors

Aug 10, 2012 | 2004 Lincoln LS

1 Answer

'01 chevy prism has the check engine light on, P0240 is the code


Hi Carla:
There are a number of things that could be causing this p0420 catalyst efficiency code. The most common thing is the catalytic converter itself is no longer functioning properly. The other likely thing is the rear O2 (oxygen) sensor is no longer working properly. Other things could include exhaust leaks, damaged exhaust pipes, damaged O2 sensor wiring/connectors, plugged catalytic converter, etc.

A P0420 code is a trouble code on OBD-II equipped vehicles. All vehicles from 1996-newer sold in North America support this generic powertrain code. This code is a pretty common one and this site is here to help the average do-it-yourself (DIY) car owner (like you) troubleshoot, diagnose, and fix their vehicle themselves when presented with a P0420 code, saving money.

If your car has multiple trouble codes (DTC's), it's always a good idea to fix them in the order they come up on the code reader. For example, if you have these codes - P0300, P0420, P0171, then you're going to want to tackle the P0300 Random Misfire code first (resolve it), and then tackle the P0420 code, etc. The reason for that is that the first code could be causing further DTCs to be set.

If you've come to this site you most likely already know that you have a P0420 code. To start, we strongly recommend you seek the services of a professional mechanic/technician if you have any doubts as to whether you can perform the repair.

Possible Solutions: Some suggested steps for troubleshooting a P0420 error code include:
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

One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into.

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

Sep 26, 2011 | 2001 Chevrolet Prizm

1 Answer

My engine light is blinking and the car feels like it is hesitating. We took it to AutoZone and had them hook it up to get the trouble shooting codes. I have a list of codes below that showed...


http://www.obd-codes.com/p0300

It appears that there is a problem with your #4 cylinder. either no spark, or fuel. The other problem you have is with your EVAP system. Have you driven with your gas cap off or loose?

Oct 25, 2010 | 1997 Lexus ES 300

1 Answer

Check engine light p0300, p0420 & mtv solenoid makes noise


P0300
1.ignition system fault spark plug ign wire coil.
2.vacuum leak, inj fault.
3.high or low fuel pressure.
P0420
1.catylist eff low bank1- cat can be defective.
2.eng misfire, vacuum leak.
3.engine oil leak into the exhaust valve guide seals.
as for the warranty i dont know.

May 04, 2010 | 2005 Chrysler Pacifica

2 Answers

5 error cods on my 2002 Jetta GLS 1.8 Turbo Engine


P0420= Catalyst System Efficiency Below Threshold Bank 1
P0300=Random/Multiple Cylinder Misfire Detected
P0301=Cylinder 1 Misfire Detected
P0172=System Too Rich Bank 1
P2181=Cooling System Performance
you need to write these down,have someone clear the codes in the car,then go for short ride and recheck which if any code reappears.it's like domino's affect,one sensor can start a chain affect with the others.

Dec 09, 2009 | 1998 Volkswagen Jetta

1 Answer

Error codes: P0420 AND P0446


the p0420 could and usaully is a bad converter.

May 28, 2009 | 1996 Oldsmobile Bravada

1 Answer

P0420 Error code, I had the sparks plugs replaced in dec...now one is misfiring again.


i dont know if this 402 code is a miss code on a jag but usually miss codes are p0300 codes. if you are hearing a ticking and you own a spray bottle, an old mechanics trick is to mist water on the plug wires while the engine is running preferrably in the dark.

May 20, 2009 | 2001 Jaguar S-Type

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