Replace O2 Sensor?
Thread Starter
Newbie
Joined: Jun 2016
Posts: 8
Likes: 0
2004 S500
Replace O2 Sensor?
Hey all! New guy here. About 3 weeks ago I acquired my first MB. It is a '04 S500. It does have 145K miles on it. For the last three weeks I have been learning a lot on here. You guys are great! I have not had to post yet because all of my questions so far have already been answered in the past. 
The first issue I had was a parking brake handle repair...solved. Thanks!
The second issue was occasional rough idle and check engine light. I did not have a code reader at the time, but performed the MAF sensor cleaning and it is idling fine now...thanks again!
The third issue is the close assist. Getting some great info here, but have not taken time to resolve...thanks again! Does anyone see a pattern yet?
Now the third issue...and point of this post.
The check engine light came back on, so I went ahead and bought a code reader. The car seems to be running fine, but the code reader reported the following...
Faults...
P0140 O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)
P0172 System too Rich (Bank 1)
P0175 System too Rich (Bank 2)
Pending Fault code...according to Torque app
P0410 Secondary Air Injection System Malfunction
So does this boil down to replacing the 02 sensor or is there a hidden meaning from your expertise and experience?
Thanks in advance!
Side note: the air filter intake tube on the passenger side of the engine has a big crack/split in the flexible portion. Not sure if pulling hot air in from the engine compartment through the air filter may be causing an issue versus fresh air from the front of the car. I have ordered another, but just wanted you to be aware of it in case it has some sort of impact on these fault code meanings.
The first issue I had was a parking brake handle repair...solved. Thanks!
The second issue was occasional rough idle and check engine light. I did not have a code reader at the time, but performed the MAF sensor cleaning and it is idling fine now...thanks again!
The third issue is the close assist. Getting some great info here, but have not taken time to resolve...thanks again! Does anyone see a pattern yet?
Now the third issue...and point of this post.
The check engine light came back on, so I went ahead and bought a code reader. The car seems to be running fine, but the code reader reported the following...
Faults...
P0140 O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)
P0172 System too Rich (Bank 1)
P0175 System too Rich (Bank 2)
Pending Fault code...according to Torque app
P0410 Secondary Air Injection System Malfunction
So does this boil down to replacing the 02 sensor or is there a hidden meaning from your expertise and experience?
Thanks in advance!
Side note: the air filter intake tube on the passenger side of the engine has a big crack/split in the flexible portion. Not sure if pulling hot air in from the engine compartment through the air filter may be causing an issue versus fresh air from the front of the car. I have ordered another, but just wanted you to be aware of it in case it has some sort of impact on these fault code meanings.
MBWorld Fanatic!
Joined: Dec 2012
Posts: 2,472
Likes: 439
From: Ball Ground, GA (N of Atlanta)
2003 S500 2007 GL450
It appears to me that you have two problems:
- The second O2 sensor on Bank 1 appears to have failed, or may have a wiring problem causing loss of signal.
- The secondary air injection system has a problem.
The two "too rich" codes are possibly a result of the first problem.
Some code readers will allow you to monitor O2 sensor output in real-time. These readings might help determine whether the circuit is disconnected, or whether the O2 sensor is giving implausible results.
The second problem with the secondary air system may be a vacuum problem, a solenoid problem, or a plugged air passage in a cylinder head.
The secondary air injection system lives under the forward engine beauty cover. Popping that cover off will allow you to visually inspect the vacuum lines on the system, and to inspect/test the electrical vacuum valves. If all of this checks out, you can pull the vacuum valves and use string trimmer cord to "roto-root" the air passages going into the cylinder head exhaust ports.
Note that none of these problems will cause the car to stop operating - the primary result will be that the car will not pass emission inspections.
- The second O2 sensor on Bank 1 appears to have failed, or may have a wiring problem causing loss of signal.
- The secondary air injection system has a problem.
The two "too rich" codes are possibly a result of the first problem.
Some code readers will allow you to monitor O2 sensor output in real-time. These readings might help determine whether the circuit is disconnected, or whether the O2 sensor is giving implausible results.
The second problem with the secondary air system may be a vacuum problem, a solenoid problem, or a plugged air passage in a cylinder head.
The secondary air injection system lives under the forward engine beauty cover. Popping that cover off will allow you to visually inspect the vacuum lines on the system, and to inspect/test the electrical vacuum valves. If all of this checks out, you can pull the vacuum valves and use string trimmer cord to "roto-root" the air passages going into the cylinder head exhaust ports.
Note that none of these problems will cause the car to stop operating - the primary result will be that the car will not pass emission inspections.
Last edited by wallyp; Jul 2, 2016 at 01:43 PM.
Thread Starter
Newbie
Joined: Jun 2016
Posts: 8
Likes: 0
2004 S500
It appears to me that you have two problems:
- The second O2 sensor on Bank 1 appears to have failed, or may have a wiring problem causing loss of signal.
- The secondary air injection system has a problem.
The two "too rich" codes are possibly a result of the first problem.
Some code readers will allow you to monitor O2 sensor output in real-time. These readings might help determine whether the circuit is disconnected, or whether the O2 sensor is giving implausible results.
The second problem with the secondary air system may be a vacuum problem, a solenoid problem, or a plugged air passage in a cylinder head.
The secondary air injection system lives under the forward engine beauty cover. Popping that cover off will allow you to visually inspect the vacuum lines on the system, and to inspect/test the electrical vacuum valves. If all of this checks out, you can pull the vacuum valves and use string trimmer cord to "roto-root" the air passages going into the cylinder head exhaust ports.
Note that none of these problems will cause the car to stop operating - the primary result will be that the car will not pass emission inspections.
- The second O2 sensor on Bank 1 appears to have failed, or may have a wiring problem causing loss of signal.
- The secondary air injection system has a problem.
The two "too rich" codes are possibly a result of the first problem.
Some code readers will allow you to monitor O2 sensor output in real-time. These readings might help determine whether the circuit is disconnected, or whether the O2 sensor is giving implausible results.
The second problem with the secondary air system may be a vacuum problem, a solenoid problem, or a plugged air passage in a cylinder head.
The secondary air injection system lives under the forward engine beauty cover. Popping that cover off will allow you to visually inspect the vacuum lines on the system, and to inspect/test the electrical vacuum valves. If all of this checks out, you can pull the vacuum valves and use string trimmer cord to "roto-root" the air passages going into the cylinder head exhaust ports.
Note that none of these problems will cause the car to stop operating - the primary result will be that the car will not pass emission inspections.
I probably shouldn't have, but I cleared the codes this morning. They have not returned yet...just sitting in the driveway idling. We are about to go for a drive though.
Hope to check on the second problem with the secondary air system tomorrow.
Thanks.
