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Check engine light

Tiny
GPOLIMPO
  • MEMBER
  • 2006 MAZDA 3
  • 1.6L
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 190,550 MILES
Hello,

I just want to ask what would be the next step on how to fix my CEL problem for KOEO/KOER (Mazda 3).

First, I have encountered CEL code P0420 catalyst efficiency below threshold (bank 1).I brought my car to an auto shop and they replace the 1 pc O2 sensor at the upstream (before catalytic converter).1 day after replacement I encountered another CEL and when they diagnose it the code extracted was P0031 Heated O2 sensor heater circuit low volt-bank 1 sensor 1 and again they replace the downstream O2 sensor (after cat converter) so all my O2 sensor were new.

Three days after while driving to work the CEL display again on my dashboard. When I returned my car for diagnostic the code was :
KOEO (Key Engine Off) demand self test
KOER (Key Engine Running ) demand Self test
Retrieve CMDTCs(Continuous Memory DTC)

It is already one and half months that my car is still encountering the same CEL problem.

What has been done were the ff:
Pull-out and Clean Cat converter - problem the same
Check for possible wire short connection, they found out wire was stuck and they fix it- problem still the same.
Clean fuel pump and replace bend hose to fuel line - still problem exist.

The next target now is to replace the muffler. How sure that this problem will be correct?
KOEO (Key Engine Off) demand self test
KOER (Key Engine Running ) demand Self test
Retrieve CMDTCs(Continuous Memory DTC)

Hope you can help us

Thank you
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Monday, May 8th, 2017 AT 9:27 PM

13 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
If it is a 420 code it is a bad converter you cannot clean them out. If it is not that code what is it. Is it still an 0031?
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Tuesday, May 9th, 2017 AT 7:04 AM
Tiny
STEVE W.
  • MECHANIC
  • 12,978 POSTS
Okay, as I read this you started with a code P0420, You took it to a shop that changed out the Bank 1 sensor 1 O2?
Then it showed a code P0031, the shop then replaced the Bank 1 sensor 2 O2

P0420 can show up if the O2 sensors are bad and sending the wrong information to the engine, but it can also be a bad catalytic converter. No way to clean a bad converter, you have to replace them.

However the P0031 code should not have them replace the Bank 1 sensor 2 oxygen sensor, it has nothing to do with that sensor, it means that the heater circuit to the first sensor they replaced has a problem. This would be like a shop changing the windshield wipers to fix a flat tire!

Perhaps the "stuck wire" they repaired was to fix the P0031 problem?

Now you still have the CEL on, what codes do you get when it is scanned?
Still the P0420? If so and the fuel trims are good and you do not have a plugged muffler or an exhaust leak then you still have a bad converter.
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Tuesday, May 9th, 2017 AT 10:03 AM
Tiny
GPOLIMPO
  • MEMBER
  • 7 POSTS
Hi Steve,

Still have CEL but no more code what the diagnostic tool read was:

KOEO (Key Engine Off) demand self test
KOER (Key Engine Running ) demand Self test
Retrieve CMDTCs(Continuous Memory DTC)

here's the photo
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Tuesday, May 9th, 2017 AT 5:23 PM
Tiny
STEVE W.
  • MECHANIC
  • 12,978 POSTS
OK, those should be menu items you select to make the tool read the codes. For instance the :
KOEO (Key Engine Off) demand self test when selected and OKed will scan the system for codes that are set and turning on the light.

Retrieve CMDTCs: are items that are scanned constantly like crank sensors, throttle position sensors, battery voltage and such. Those can set a pending code which if the problem stops will erase itself without setting a light.

What make model is the scan tool you have? I'll look up the manual and see what else it can do that might help you.
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Tuesday, May 9th, 2017 AT 7:52 PM
Tiny
GPOLIMPO
  • MEMBER
  • 7 POSTS
The scan tool model we use is Launch x-431 GDS. We re-learn the car and reset but after few days of driving @ 175km mileage we experienced CEL and the same problem we seen on the scan tool.

KOEO (Key Engine Off) demand self test
KOER (Key Engine Running ) demand Self test
Retrieve CMDTCs(Continuous Memory DTC)

Herewith is the scan tool we are using
Image (Click to make bigger)
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Wednesday, May 10th, 2017 AT 10:03 PM
Tiny
STEVE W.
  • MECHANIC
  • 12,978 POSTS
This is the image you posted earlier. That should be a selection menu. You pick one of the options and let the system run the test. From a book covering these tests -

Quick Test
The quick test is divided into 3 specialized tests:
1. Key On Engine Off (KOEO) On-Demand Self-Test
2. Key On Engine Running (KOER) On-Demand Self-Test
3. Continuous Memory Self-Test

The quick test checks the integrity and function of the electronic engine control (EEC) system and outputs the test results when requested by the scan tool. The quick test also provides a quick check of the powertrain control system, and is usually carried out at the start of each diagnostic procedure with all
accessories off. The quick test is also carried out at the end of most pinpoint tests for verification of the repair and to make sure no other concerns are incurred while repairing a previous concern. A system pass is displayed when no diagnostic trouble codes (DTCs) are output and a scan tool communication error does not exist. System pass means that hardware monitored by the powertrain control module (PCM) is
functioning within the normal operating limits. Only a system pass, a DTC, or an incomplete on board diagnostic (OBD) drive cycle (P1000) is displayed.

Key On Engine Off (KOEO) On-Demand Self-Test
The KOEO on-demand self-test is a functional test of the PCM carried out on-demand with the key on andthe engine off. This test carries out checks on certain sensor and actuator circuits. A concern must be present at the time of testing for the KOEO self-test to detect the concern. When a concern is detected, a DTC is output on the data link at the end of the test as requested by the scan tool.

Key On Engine Running (KOER) On-Demand Self-Test
The KOER on-demand self-test is a functional test of the PCM carried out on-demand with the key on, the engine running and the vehicle stopped. A check of certain inputs and outputs is made during operating conditions and at a normal operating temperature. The brake pedal position, transmission control, and the power steering tests are part of the KOER on-demand self-test and must be carried out during this operation if applicable. A concern must be present at the time of testing for the KOE
R on-demand self-test to detect the concern. When a concern is detected, a DTC is output on the data link at the end of the test as requested by the scan tool.

Only after you run the tests will you see if there are trouble codes.

If you select one of the tests and the scan tool doesn't start the tests, either the DLC isn't working properly and the scan tool cannot talk to the system, OR the scan tool itself has a problem.
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Thursday, May 11th, 2017 AT 4:52 AM
Tiny
GPOLIMPO
  • MEMBER
  • 7 POSTS
Okay, we will carry out any of the test tomorrow to check if the car have still trouble codes.
I'll update you the out come.

Thanks for the inputs
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Thursday, May 11th, 2017 AT 10:07 PM
Tiny
STEVE W.
  • MECHANIC
  • 12,978 POSTS
Post back once you get a code and we can continue.
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Friday, May 12th, 2017 AT 12:30 AM
Tiny
GPOLIMPO
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  • 7 POSTS
We re-scanned the car with a different scan tool and here is the result. Do I need to replace my cat converter?
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Sunday, May 14th, 2017 AT 8:45 PM
Tiny
STEVE W.
  • MECHANIC
  • 12,978 POSTS
You already tried to clean it and you're not showing the sensor codes so I would say the convertor is bad.
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Monday, May 15th, 2017 AT 3:55 AM
Tiny
GPOLIMPO
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  • 7 POSTS
Someone is offering me for a 2nd hand catalytic converter, would it work for my car?
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Monday, May 15th, 2017 AT 6:20 PM
Tiny
GPOLIMPO
  • MEMBER
  • 7 POSTS
Have you known someone who install a 2nd hand cat converter that works well?
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Monday, May 15th, 2017 AT 6:22 PM
Tiny
STEVE W.
  • MECHANIC
  • 12,978 POSTS
I've never installed a used cat, in my area that is actually illegal. The questions I would ask are, Why was it removed? What was wrong with the vehicle it came from?
Those two because the cat you get could be as bad as the one you have already.
The choice is yours.
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Tuesday, May 16th, 2017 AT 4:20 AM

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