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I have a 2004 Honda Civic EX Manual and I have the issue that my check engine light keeps coming on. The car is running great so other than the light coming on thats the only issue. So my problem is that when I check the engine light code some times it will throw the P0134 code and then ill erase it and then some other times it will throw the P0138 code. It never throws both codes at the same time and its never one after another it could throw the P0134 a bunch of times and all of the sudden it will throw the P0138 a few times. Its completely random! Can anyone explain to me what I should do? I don't want to replace an O2 sensor if thats not the issue! Thanks for all the help in advance!
If you think a good mechanic is expensive, try hiring a bad one
Joined: Dec 2011
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Re: 2004 honda civic P0134 and P0138 codes
I'd replace the bad sensors, using the correct original brands.
(both are probably Denso, but check the brands in your car if they are both original.......and the front sensor is an AF sensor, not a regular O2 sensor)
I'd replace the bad sensors, using the correct original brands.
(both are probably Denso, but check the brands in your car if they are both original.......and the front sensor is an AF sensor, not a regular O2 sensor)
So you think both sensors are bad? Could it be my cat making those codes get thrown? Or is it deff just those two sensors?
If you think a good mechanic is expensive, try hiring a bad one
Joined: Dec 2011
Posts: 32,017
Likes: 256
From: Midwest. Aiming about mid-chest
Rep Power: 518
Re: 2004 honda civic P0134 and P0138 codes
Originally Posted by HondaCivicNY24
So you think both sensors are bad?
Yes.
Got a bunch of miles on the car? Sensors don't last forever.
Also, check the definition of each fault code to better understand the failures.
Could it be my cat making those codes get thrown?
Unscrew each sensor and inspect for physical damage to the thimble. If no damage, then it's not a cat issue.
(Not bloody likely, but I saw it happen once so it's worth mentioning)
Note: the computer won't run self tests on the catalytic converter while there are O2 sensor fault codes.
There is the possibility you could get a cat failure code (P0420) after good sensors are installed.
Got a bunch of miles on the car? Sensors don't last forever.
Also, check the definition of each fault code to better understand the failures.
Unscrew each sensor and inspect for physical damage to the thimble. If no damage, then it's not a cat issue.
(Not bloody likely, but I saw it happen once so it's worth mentioning)
Note: the computer won't run self tests on the catalytic converter while there are O2 sensor fault codes.
There is the possibility you could get a cat failure code (P0420) after good sensors are installed.
Okay all that sounds great! I will have to unscrew the two sensors and check them out. The car has 176,000 miles on it and i Just replaced the motor so this is the last issue. Anything specific that I should look for on the sensor that could be broken? Also is there anyway to test my sensors or clean them?
If you think a good mechanic is expensive, try hiring a bad one
Joined: Dec 2011
Posts: 32,017
Likes: 256
From: Midwest. Aiming about mid-chest
Rep Power: 518
Re: 2004 honda civic P0134 and P0138 codes
Originally Posted by HondaCivicNY24
The car has 176,000 miles on it
At that mileage, failures are not unexpected.
Anything specific that I should look for on the sensor that could be broken?
If the cat broke apart inside, it could damage the "thimble" (the metal covering the the sensor element) or break the end of the sensor off completely:
See the difference?
Also is there anyway to test my sensors or clean them?
The computer tests them. Well, it reports anomalies as it sees it electrically.
You should check the wiring from the sensor connection to the computer and power, etc. per service manual troubleshooting and diagnosis for each code though.
If the cat broke apart inside, it could damage the "thimble" (the metal covering the the sensor element) or break the end of the sensor off completely:
See the difference?
The computer tests them. Well, it reports anomalies as it sees it electrically.
You should check the wiring from the sensor connection to the computer and power, etc. per service manual troubleshooting and diagnosis for each code though.
Cleaning? No.
Okay perfect! I will check those out this week and get back to you as to what I found! Thank you again for all the great information I appreciate it tremendously!
