Mil p0421, p0431
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1st Gear
Joined: Sep 2010
Posts: 409
From: Boston MA
Mil p0421, p0431
Check engine lights on re left and right warmup Cat efficency.
If no bad CAT symptoms and passed inspection, OEM ECU threshold was set too narrow range. A little out of spec then the CEL pops out.
Audi TSB about fixing this low threshold problem on certian Audi year/model by flashing the ECU/ECM with the updated software. This will clear this MIL problems. Not all Audi dealers will do flashing ECU though.
Dealer will want over $2,800 to replace both CAT converters.
"Mini-Cat-CEL-Fix" and it works. http://www.bigdaddiesgarage.com/
If no bad CAT symptoms and passed inspection, OEM ECU threshold was set too narrow range. A little out of spec then the CEL pops out.
Audi TSB about fixing this low threshold problem on certian Audi year/model by flashing the ECU/ECM with the updated software. This will clear this MIL problems. Not all Audi dealers will do flashing ECU though.
Dealer will want over $2,800 to replace both CAT converters.
"Mini-Cat-CEL-Fix" and it works. http://www.bigdaddiesgarage.com/
Last edited by bigdadi; Oct 23, 2010 at 08:58 AM.
1st Gear
Joined: Jun 2010
Posts: 272
From: Chesapeake Bay area, Virginia
The test for these codes is to check the O2 sensors and control systems. The CAT is not the issue until the O2 sensor is checked. Get the sensors monitored in real time to see what the O2 sensors are doing. I would also look carefully at the MAF sensor during this test to see if it is working right.
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