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OBD codes P0128 and P0420 set..how to fix

OBD code P0128 set then cleared. 1 week and a refueling and the P0128 and P0240 is set.

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6 Suggested Answers

6ya6ya
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Posted on Jan 02, 2017

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chuck943
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SOURCE: Ford windstar OBD II code P1537/38, P0171 and P0420

It could all be related.P1537/38 are the intake manifold runner controls are stuck open.They are controlled by vacuum solenoids.The P0171 is bank one of the engine is running lean,usually caused by a vacuum leak, P0420 is catalytic converter efficiency code. The computer monitors the switch rate of the front 02 sensors and compares it to the switch rate of the rear 02 sensors to tell if catalytic converter is doing its job. Now if the front 02 is not switching properly then this will cause this test to fail and set this code.
Look on bottom section of the intake manifold at the back of engine(where tranny bolts up) you should see the vacuum motors there on the intake,these are the control motors for the intake manifold runners.Make sure the vacuum lines are hooked up and lines are not leaking. Also you will see a lever from it to intake make sure they move and are not binding.

Posted on Mar 11, 2009

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  • 11 Answers

SOURCE: p0240 catalyst system below threshold bank 1

This code has plagued technicians nationwide. This code is set because the computer is not reading the proper signals from the O2 sensors. This could either be related to faulty sensors or just a weak catalytic converter. There is also other solutions where you can dampen the O2 sensor signal but it's extremely difficult for a do-it-your-selfer to do.

Posted on Sep 03, 2009

bschilz
  • 2049 Answers

SOURCE: check engine light-on OBD code's P0420 &

The codes are Catalyst System Efficiency Below Threshold (Bank 1)&(Bank 2).

The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check Engine light if the readings of the two sensors are similar. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.

A code P0420 may mean that one or more of the following has happened:

  • Leaded fuel was used where unleaded was called for
  • An oxygen sensor is not reading (functioning) properly
  • The engine coolant temperature sensor is not working properly
  • Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
  • Retarded spark timing
  • The oxygen sensors in front and behind the converter are reporting too similar of readings
Some suggested steps for troubleshooting a P0420 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.

Posted on Oct 06, 2009

  • 14036 Answers

SOURCE: What can keep causing Check engine code P0128

CODE P0128- THERMOSTAT MALFUNCTION. POSSIBLE CAUSES 1. ECT SENSOR IS OUT OF CALIBRATION. 2. CHECK THE OPERATION OF THE THERMOSTAT IT MAY BE STUCK OPEN.3.INSPECT FOR LOW COOLANT LEVEL OR FOR AN INCORRECT COOLANT MIXTURE.

Posted on Jan 06, 2010

  • 1861 Answers

SOURCE: how to erase toyota camry code obd 1

Hello, and welcome to FIxYa.

To erase the check engine light on a 1994 Camry, open the hood, and, in the engine compartment fuse box, remove the blue 15 amp EFI fuse for one minute. This will clear the codes. If you have a hard code; ie a malfunctioning sensor, the light will come right back on.

Thanks for choosing FixYa for assistance.

Posted on Mar 12, 2010

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My 2005 chevy equinox keeps showing problem code P0420 How do I fix this problem?


0 2 sensor near the catalytic converter or

replace the catalytic converter

The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check Engine Light if the readings of the two sensors are similar.

Read more at: https://www.obd-codes.com/p0420
Copyright OBD-Codes.com

https://www.obd-codes.com/p0420

Feb 03, 2017 | Cars & Trucks

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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

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1 Answer

What is the normal ghead or coolant operating temp tha world report on a Scanguage


the thermostat opoens at 195 degrees Farenheit, so any range from 175-200

also, if your thermostat fails in the open position, you'll set a P0128 OBD-II Trouble Code

Read more at: http://www.obd-codes.com/p0128
Copyright © OBD-Codes.com

Apr 08, 2015 | 2005 Ford Escape Hybrid

1 Answer

What does error code p0128 mean


This means that the engine's PCM detected that the engine has not reached the required temperature level within a specified amount of time after starting the engine. The intent of the P0128 code is to indicate a faulty thermostat

Read more at: http://www.obd-codes.com/p0128
Copyright © OBD-Codes.com

Feb 04, 2015 | Cars & Trucks

1 Answer

P0128 code engine code


  • Low engine coolant level
  • Leaking or stuck open thermostat
  • Faulty cooling fan (running too much)
  • Faulty coolant temperature (ECT) sensor
  • Faulty intake air temperature (IAT) sensor
source:http://www.obd-codes.com/p0128

Oct 02, 2012 | 2006 Chevrolet Colorado

2 Answers

Catalytic converter code bank 1 p0240


What I think Bank 1 usually refers to the O2 sensor before catalytic converter. I have been told in the past many thing can set it off. I have gotten them before for O2 sensor and took my negative battery cable off the batter and it cleared the code. Sometimes it comes back sometimes not. I did find some info.
https://www.yourmechanic.com/article/p0240-obd-ii-trouble-code-turbocharger-boost-sensor-b-circuit-range-performance-by-jay-safford
One thing I need to add if you pull the cable off the battery and your radio has a antitheft program in it you will have to provide a code to get your radio working again.

Aug 21, 2017 | 2003 Ford Taurus

4 Answers

Po128 is the code. What's the problem


Well, I can't give you any specific information regarding your vehicle because you forgot to mention what kind of vehicle you have. (This is kinda important if you really want some help figuring out what is wrong with your car)

The "Generic OBD" of code P0128 is "Coolant Temperature Below Thermostat Regulating Temperature"

The most likely cause is a stuck-open thermostat, however, I have also seen defective Engine Coolant Temperature (ECT) sensors also cause this code.

Jun 13, 2011 | Chevrolet TrailBlazer Cars & Trucks

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