My friend read out these codes with his Durametric. Anyone recognize them and can give some insight as to their meaning?

DME codes are PO492, fault code 208, secondary air system, bank 2

and

PO491, bank 1.

Car will be going to the shop in about a week. Any advance knowledge will help with turn around time. Thanks for looking.

 

Your air injection system seems to be malfunctioning. This is strictly an emissions device and would not affect the vehicles performance and/or power output. Main component of this air injection system is the electric air pump which functions for a few seconds at cold start. It pumps air bringing catalytic converters up to operating temperatures very quickly for lower tailpipe emissions.

The system components need to be tested individually by a competent technician in order to isolate failure. Hope this helps you understand how the system functions. Most can only guess which is the likely culprit without physically looking at it.

 

Credit to Loren at Renntech:


P0491 Secondary Air Injection System, Bank 1 - Insufficient Flow
P0492 Secondary Air Injection System, Bank 2 - Insufficient Flow

Possible cause of fault
- Electrical fault in power supply or line between relay and secondary air injection pump
- Secondary air injection pump relay mechanically faulty
- Mechanical fault in electrical secondary air valve
- Pneumatic secondary air valve faulty/sluggish
- Electrical fault in secondary air injection pump
- Mechanical fault in secondary air injection pump or secondary air injection pump blocked
- Vacuum system leaking
- Air hose to secondary air injection pump slipped off or constricted

 

How does bank 1 and bank 2 relate to this system?

 

Ard has posted a great schematic depicting the engine vacuum routing.

The secondary air system begins functioning when the engine control unit electrically triggers on the secondary vacuum solenoid #7 when necessary.

That's when #6 air control valve is opened by vacuum allowing air which the electrical air pump creates (air pump not shown in above photo) to enter both bank 1 and 2.

Bank 1 Cylinders 1 thru 3
Bank 2 Cylinders 4 thru 6

A knowledgeable tech can diagnose this system sometimes very quickly with the use of a porsche tester by activating individual components without disassembly. The vacuum lines must be examined visually or with smoke tester for leaks.

 

I am not entirely familiar with the 996tt system, but the DME looks at the O2 sensor values during cold start (when the airpump is running) to make decisions about "low flow". The system should be seeing motor current, so a bad motor will not give that code (there is a specific code for no motor current).

My guess is one component that controls airflow to both banks.

 

Larry, I had this code early on, It was a leaking plastic connector for the vacuum hose. Check the the vac connections on the DV or the F pipe for any leaks.

 

Thanks guys, this will give my tech some idea of what's going on before I get there. He has the Porsche computers for the diagnosis and tests.