P0420 Code

[vettatude]

I just bought a 98 A4 with a Borla Cat Back system on it. I didn't like the sound of the Borla's so I put a stock system back on until I figure out what I want. A day later I trip a check engine light with a P0420 code. I have reset the ecu and cleared the codes but it keeps coming back. Questions: Will the ecu ever re-learn the stock flow characteristics? What if it is a cat going bad? SHould I just get some o2 sims? Please help, this light is driving me nuts.

Thanks,

Bill

 

[c4c5specialist]

Hi there,
Well, first, did anyone modify the catalytic converter system on your car???? IF not, you are in luck, as the converters have a 8yr/80k warranty from the factory, per EPA guidelines. HOWEVER< as long as they are not modified from the factory configuration.
As far as the Borla, or stock system causing this, no, it would not.
If you are getting this code only, this is showing an issue with the converter itself.
I do NOT, in anyway, suggest installing o2 sims, they are not good for the car, in anyway.
Allthebest, c4c5

 

[vettatude]

Well, no this isn't the only code. I got several:

TCS: C1276H
BCM: U1016H
IPC: U1016H
Radio: U1016H
LDCM: U1016H
RDCM: U1016H
A6-SCM: U1016H
RFA: U1016H

I understand those are loss of communication codes, except for the C1276H. I had driven the car two weeks w/o any trouble. Replaced the cat back with stockers and it started acting up. The only modification to the mid pipe is after the cats. The borla system replaced the H section with a resonator. I had that replaced with two straight pipe sections. How would the dealer be able to tell if the cats are bad? Emissions test?

Thanks

 

[c4c5specialist]

Hi there,
Well, the warranty is void on the converters.
The modification will change the way the converters operate, sorry to say.
Anyway, the 1276 is for your ABS, and would have nothing to do with the converters.
Driving the car for 2 weeks might not kick the light. The diagnostic scenario is very specific for the code to set.
Sorry to say, but you may have to replace it.
A smog test is possible, but per EPa guidelines, any check engine light on an OBD 2 equipped car, counts as an emissions failure.
Allthebest, c4c5

 

[vettatude]

Thanks for the info. I'm not too worried about being in compliance with the DEQ or EPA since we don't have emissions tests where I live, and it doesn't seem to be going into any failsafe or reduced power mode because of it. I just don't want the light coming on and staying on when something else could be an issue. I unhooked the battery last night and re-connected it this morning. Drove 15 miles to work and no light. It was consisitantly giving me the light the last two days on my commute. I'll keep my fingers crossed. Thanks again!!

Bill

 

[SpeedracerZ06]

A friend has this same code and is also having a misfire situation. This is the only active code he has. His car shows History codes of C0221, C0222 (wheel sensor) even though he has a 2001 Z06, and U1064 Loss of communications with the DCM. What is the DCM? What should I look for in Autotap to provide more data? He isn't getting any type of misfire code. Thanks!

Jeremy

 

[c4c5specialist]

HI there,
DCM is for the door control module.
I would suggest that you check which door control module, as Autotap is very generic. I would really not worry about the DCM.
Your other tire wheel speed sensor codes could be from a dyno run, or spinning the tires long enough for the fronts not to spin.
As for the misfire, it would show, and I would not worry.
Allthebest, c4c5

 

[vettatude]

BTW, just as a followup. I had some exhaust work done around the same time I changed to stock mufflers. There was some welding done by the O2 sensors. I dropped the mid-pipe and had a look. There was a very small hole where the welding was that was right by the O2 sensor. It was sucking cold air right by the sensor and thus tripping a MIL. I got it tacked up and haven't had a MIL since. Thanks for the help.