[sidatu]

Hello,
My 2007 Honda civic has been recently giving less MPG (25 MPG / 9.5 l/100km at max - City/Highway combined), I've never had better fuel economy than this.
Its a DX Automatic with 251000 km / 156000 miles.

I just got an OBD2 scanner tool and after reading the live data,
I found out that the Upstream oxygen sensor was showing no data at all (No response), and still it didn't threw any CEL whatsoever.

I changed the spark plugs (NGK OEM recommended) just 2000 km/1250 miles ago. Air filter looks good.

The live data was as follows:

OXYGEN SENSOR 1 VOLTAGE: No response
OXYGEN SENSOR 1 FUEL/AIR: No response
FUEL TRIM (LONG) B1: -12.5%
MAF RATE (I think it was idling at normal RPM): 2g/s
OXYGEN SENSOR 2 VOLTAGE: 0.53 V

The fuel trims had a bit of variation every time I check it, but every time, it was in the negatives (Short & Long) which I believe means the ECU is removing the extra fuel.

Does this NO RESPONSE and NO CEL means a lazy oxygen sensor?

Thanks!

 

[ArcadeTechGW]

How long did you allow it to run? The system has to heat up, so if you do this cold, it won't register.

Try running the car at speed for at least 10 to 15 minutes before you pull codes.

 

[sidatu]

How long did you allow it to run? The system has to heat up, so if you do this cold, it won't register.

Try running the car at speed for at least 10 to 15 minutes before you pull codes.

Hello, no matter how long do I run it for, it still gives me the same results.

 

[ArcadeTechGW]

Hello, no matter how long do I run it for, it still gives me the same results.

Then you have a different problem. Have you tried cleaning out your EGR galleries? My galleries were full of carbon. I had changed the Mass Air Flow Sensor, EGR valve, Spark Plugs, and both O2 sensors. That was all that was left.

Search for it - there are YouTube videos. It isn't hard to do, and it solved my problem.

I broke up the carbon with a screwdriver - it was fragile, but had the whole gallery plugged. Then I used my shop vac to get it out.