# Service bulletin A26162720439811

A bulletin is a manufacturer's communication to its dealers, as NHTSA indexes it. The summary is NHTSA's. The document is the manufacturer's: read it at NHTSA. A bulletin is not a recall, and listing a model year does not mean every vehicle of it is concerned.

- Type: Service bulletin
- NHTSA id: 10093601
- Published by NHTSA: 2017\-03\-03
- Manufacturer's number: A26162720439811
- Manufacturer's date: 2016\-04\-14
- NHTSA component: ENGINE AND ENGINE COOLING:EXHAUST SYSTEM:EMISSION CONTROL:CATALYTIC CONVERTOR

## NHTSA's summary

THIS BULLETIN INFORMS THE READER TO RECEIVE DIAGNOSIS OR AUTHORIZATION FROM THE TECHNICAL ASSISTANCE CENTER BEFORE REPAIRING AN ISSUE WITH THE CATALYTIC CONVERTER THAT CAUSES DTC P042000

## The document

No address for NHTSA's copy can be built for this communication. Ask the dealer for it by the manufacturer's number.

## Components

Engine, Exhaust and emissions, Catalytic converter

## Trouble codes named

P0420

## Vehicles listed

- 2009 to 2010 AUDI A4
- 2010 to 2011 AUDI A5
- 2010 to 2011 AUDI A5 CABRIOLET
- 2009 to 2010 AUDI ALLROAD
- 2010 to 2011 AUDI Q5

## Other bulletins for the same vehicles and component

- [A011257 2028344\-](/bulletins/10122803.md), 2017-11-08, Service bulletin: ENGINE AND ENGINE COOLING:EXHAUST SYSTEM:EMISSION CONTROL:CATALYTIC CONVERTOR; ENGINE AND ENGINE COOLING. Supersedes Technical Service Bulletin Group 01 number 12\-51 dated July 18, 2012. Noises/inconsistent engine operation after cold start during the catalyst heating phase. The customer may interpret this engine roughness as misfiring. To comply with the legal requirements on exhaust gas emissions according to the LEV\-1 and LEV\-2 standards, a high exhaust gas quality must be ensured. The necessary catalyst only operates at a temperature over 300°C \(572°F\). To achieve this, the catalyst is heated up. The catalyst heating phase is achieved by a late ignition angles and by introducing additional fresh air to the exhaust valves \(secondary air system\). Late ignition angles make sure that the exhaust gas from the cylinders has a higher temperature. This exhaust gas includes fuel that is un\-burnt, and was deliberately injected into great quantities. The secondary air system adds fresh air to the exhaust gas as it leaves the cylinder and the extra fuel is burnt. As a result, the temperature of the exhaust gas and of the catalyst increases quickly. The afterburning in the exhaust manifold before catalyst changes the sound characteristic of the engine. This heating\-up of the catalyst, including afterburning, is normal and has no effect on the service life of the engine. During this catalyst heating phase the engine has increased idle speed, may have increased vibrations, and a different sound characteristic. Depending on conditions the time of the catalyst heating phase varies.
- [A01166520354544](/bulletins/10094894.md), 2017-03-14, Service bulletin: ENGINE AND ENGINE COOLING:EXHAUST SYSTEM:EMISSION CONTROL:CATALYTIC CONVERTOR. THIS TECHNICAL SERVICE BULLETIN CONTAINS INSTRUCTIONS FOR PRESSURE WASHING PORTS TO RESOLVE AN "AIR SYSTEM \-\- ACTION REQUIRED" MESSAGE.

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