Code 0138

M

Michal

Guest
#1
2000 Integra
code p0138
I have read some people saying that if i keep driving having this code my fuel economy will suffer.
Since this code means high signal voltage from post cat. sensor, and the computer does not use the post cat. sensor for fuel trim but to monitor cat. performance, why would this high voltage on O2S12 cause a rich condition?
The car in fact is running rich cause I can see black smoke on heavy acceleration, and the avg. reading for the pre cat. sensor is 560 mV, not 450.
Also the mileage is poor.
Any explanation would be appreciated.

Michal
 

jjm

Hero Member
Joined
Dec 1, 2006
Messages
349
Likes
0
Points
0
Location
NYC
#2
I don't think P0138 is what's causing the rich condition; seems the condition is already there, and the sensor is responding appropriately, setting the DTC.

I'm surprised other codes aren't being set. Is your scantool capable or reading "soft" or pending codes, because I'll bet some are there.

Got any fuel trim numbers?

First thing I'd check is fuel pressure, then pull the plugs see if any of them are sooted up (evidence of a leaky injector). Could even be an evap problem.

By the way which Integra? GS, GSR, LS, Type-R?

Joe

If you found this information helpful, please support BATAuto!

 
M

Michal

Guest
#3
Thank you very much Joe,
I thought that the post cat sensor should not be making the car run rich.
I do think however that the sensor or conection is bad as it sends a constant voltage signal of 1.275 V
The trim numbers were as follows in freeze frame
Short time FT= 1.6%
Long time FT= -0.8%

I can find a lot of references to what the pre cat O2 sensor readings should be but It is not so clear for the post cat sensor.
I know it should not oscilate as fast as the pre cat sensor, and if it does the cat is "pooched", but what should the signal look like, should it average at 0.45V?
I do not think I found any soft codes but, I can't remember exactly, next time I check the car I will look for those.

As I mentioned the average signal over 10 min of highway driving from pre cat O2 sensor was 0.564V which indicates that the car is running rich.

Why would a leaky injector cause rich condition?

This is a GSR.
Again thanks for this response.

Michal
 

Transman

Receptionist & Complaint Dept.
Joined
Nov 14, 2006
Messages
2,953
Likes
0
Points
0
Location
New Jersey
Website
www.edsofvineland.com
#4
Those trim numbers don't point to a rich condition, What are you getting for a Maf reading at idle and full throttle? A sticking/leaking injector will not stop allowing fuel into the cylinder when it is supposed to so while the other injectors are firing the other cylinders, the bad one is still adding fuel to the cylinder. When that cylinder fires, if it can, there is extra unburned fuel exiting into the exhaust which you see as black smoke. Have you checked the fuel pressure? This is a very common problem where the regulator causes more pressure than the injectors can stop, this causes all cylinders to be rich. This is a more common cause for the black smoke syndrome.= and a simple fuel pressure test will usually tell the tale. Post back, Transman