1998 Honda Accord Oxygen Sensor

Tiny
ANOBLE1
  • MEMBER
  • 1998 HONDA ACCORD
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 161,000 MILES
Hello, I have a 1998 Honda Accord that has a check Engine light on. It reads: P0420. Catalyst System Efficiency Below Threshold (Bank 1) I think. But we put a Bosch O2 sensor under the hood. Along with a new catalytic converter. It was not the stock one that comes from Honda. That one was too expensive. The engine light come on every 20 miles or less when it gets cut off. The same code comes up. I am averaging 21mpg before it was around 30mpg. I am guessing it is that Bosch o2 sensor? What kind should I get? Please help.
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Tuesday, July 6th, 2010 AT 8:47 AM

7 Replies

Tiny
KHLOW2008
  • EXPERT
Hi anoble1,

Thank you for the donation.

P0420 is a fault with the catalytic converter and not the O2 sensor. Check for leaks at the catalytic converter.

DTC P0420: CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD
NOTE:
If some of the DTCs listed below are stored at the same time as DTC P0420, troubleshoot those DTCs first, then recheck for DTC P0420.

P0137, P0138: Secondary HO2S (Sensor 2)

P0141: Secondary HO2S (Sensor 2) Heater

1. Reset the ECM/PCM.

2. Start the engine. Hold the engine at 3,000 RPM with no load (in Park or neutral) until the radiator fan comes on.

3. Except F23A4 SULEV engine: Test-drive at 40-55 mph (64-88 km/h) for approx. 2 minutes. Then decelerate for at least 3 seconds with the throttle completely closed. Then reduce the vehicle speed to 35 mph (56 km/h), and try to hold it until the scan tool indicates FAIL or PASS as the TWC test result.

F23A4 SULEV engine: Test-drive at 50-55 mph (80-88 km/h) for approx. 2 minutes. Then decelerate for at least 4 seconds with the throttle completely closed. Then accelerate to 55 mph (88 km/h), and try to hold it until the scan tool indicates FAIL or PASS as the TWC test result.

Is the test result FAIL?

YES -Check the three way catalytic converter (TWC). If necessary, replace the TWC.

NO -Intermittent failure, system is OK at this time.
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Tuesday, July 6th, 2010 AT 11:16 AM
Tiny
ANOBLE1
  • MEMBER
I have tried this test before. I am not sure what you mean by scan tool. When I did the test I used a Innova 3160 and left it plugged into the car. It did not read pass or fail.
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Tuesday, July 6th, 2010 AT 12:25 PM
Tiny
KHLOW2008
  • EXPERT
Not all scanners are able to determine the catalytic condition. I am not familiar with the mentioned so do not know if it has that capabilities.

If the code comes back on, it means fail.

Some after market catalytic converter are not compatible as it might be working out of the specified range.
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Tuesday, July 6th, 2010 AT 12:35 PM
Tiny
ANOBLE1
  • MEMBER
Okay, I guess the test is fail. What do I do now? I'm not familiar with a TWC and that stuff.

Thanks
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Tuesday, July 6th, 2010 AT 12:37 PM
Tiny
KHLOW2008
  • EXPERT
You mentioned replacing with a new catalytic converter, does it come with a warranty?

If yes, you should get them to replace it and retest. The ones installed could be faulty.
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Tuesday, July 6th, 2010 AT 12:48 PM
Tiny
ANOBLE1
  • MEMBER
Does it have to be an OEM catalytic converter?
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Monday, August 16th, 2010 AT 2:39 PM
Tiny
KHLOW2008
  • EXPERT
Not really necessary but after market comes in different quality and the installation work plays a part
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Monday, August 16th, 2010 AT 3:07 PM

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