2004 Audi A6 1.8T - Intermittent P0420 and P0130
10-08-2018, 09:53 AM
#1
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2004 Audi A6 1.8T - Intermittent P0420 and P0130
Hello everyone!
So I bought this car a few months back from a colleague because he sold it so cheap. One reason that he sold the car so cheap was that it had several error codes he didn't wanna deal with.
I managed to fix them all pretty easily except these two which I've been driving with for a while now...
1. P0420 - Catalyst System Efficiency Below Threshold
2. P0130 - O2 Sensor Circuit Malfunction (Bank 1, Sensor 1)
I have changed the upstream O2 sensor and checked for vacuum leaks but to no avail. I have driven about 5 000 km (3 000 miles) with these error codes and the funny thing is that the engine runs pretty good despite the codes.
If it weren't for the check engine light I probably wouldn't have suspected anything. The P0420 appears about every 300 miles of driving when i clear the code. One interesting thing I have found though is that I only get the P0130 code if I drive several short distances. I have been commuting long distances lately and even though the P0420 eventually shows up, the P0130 doesn't.
What do you guys make of all this? Could a bad catalytic converter be my "only" problem here or is it a mix of problems?
Any answers and ideas would be really appreciated!
So I bought this car a few months back from a colleague because he sold it so cheap. One reason that he sold the car so cheap was that it had several error codes he didn't wanna deal with.
I managed to fix them all pretty easily except these two which I've been driving with for a while now...
1. P0420 - Catalyst System Efficiency Below Threshold
2. P0130 - O2 Sensor Circuit Malfunction (Bank 1, Sensor 1)
I have changed the upstream O2 sensor and checked for vacuum leaks but to no avail. I have driven about 5 000 km (3 000 miles) with these error codes and the funny thing is that the engine runs pretty good despite the codes.
If it weren't for the check engine light I probably wouldn't have suspected anything. The P0420 appears about every 300 miles of driving when i clear the code. One interesting thing I have found though is that I only get the P0130 code if I drive several short distances. I have been commuting long distances lately and even though the P0420 eventually shows up, the P0130 doesn't.
What do you guys make of all this? Could a bad catalytic converter be my "only" problem here or is it a mix of problems?
Any answers and ideas would be really appreciated!
10-08-2018, 10:08 AM
#2
AudiWorld Senior Member
You changed the O2 sensor it specifies as the problem and still get the same error code? If so, sounds like it is not the sensor itself but the circuit or wiring to the sensor. Is this car all stock or have there been modifications? What are the actual fuel trim numbers, long and short term? If you reset or clear the codes does it eventually go back to the same fuel trim numbers? I expect the 0420 is related to the same issue, meaning you should resolve the 0130 first. But, ignoring the O2 problem if it is a true problem, meaning the fuel trim is way out there, can take out your cat. What spark plugs are you running? Have you looked at them?
10-08-2018, 10:45 AM
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You changed the O2 sensor it specifies as the problem and still get the same error code? If so, sounds like it is not the sensor itself but the circuit or wiring to the sensor. Is this car all stock or have there been modifications? What are the actual fuel trim numbers, long and short term? If you reset or clear the codes does it eventually go back to the same fuel trim numbers? I expect the 0420 is related to the same issue, meaning you should resolve the 0130 first. But, ignoring the O2 problem if it is a true problem, meaning the fuel trim is way out there, can take out your cat. What spark plugs are you running? Have you looked at them?
"Is this car all stock or have there been modifications?" Not that I know of. The previous owner wasn't that kind of guy and he was the second owner of the vehicle since a decade back.
"What are the actual fuel trim numbers, long and short term? If you reset or clear the codes does it eventually go back to the same fuel trim numbers?" I haven't looked to much into this, but I guess I could. I have a proper scan tool.
"What spark plugs are you running? Have you looked at them?" NGK plugs that I got shortly after I purchased the car. An ignition coil gave up soon after I got it so I decided to change the spark plugs while I was at tit. The old ones looked worn for sure but they were pretty old. I haven't looked at the new ones since I replaced them though.
10-08-2018, 11:12 AM
#4
AudiWorld Super User
There are wires in the harness between the sensor wires and the ECU, so don't be so quick to discount bad wiring.
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