In a recent case that came to the Autobiz Technical Helpline, a garage was having problems with a 2012 Audi Q5 2.0 TDi CGLB with multiple unrelated fault codes. It did not drive well, it was continually stalling, and multiple errors were recorded in the engine ECM.

The fault codes included:

• P0322 Engine Speed Sensor Signal
• P204A Reductant Pressure Signal
• P2127 Pedal E Signal
• P0651 Reference Voltage B Circuit/Open
• P203A Reductant Level Signal

As these faults are on different components, and different circuits, we decided on an alternative approach to this diagnosis. We all have our favourite technical data programs, that we use for wiring diagrams and possible known issues. We decided to take this route in this case, before testing multiple circuits, with the thought that this could save some time. We often use this very capable, well-known service from Autofrontal. And we supply some of our known fix data for them to create and modify their technical bulletins. These bulletins assist other technicians with their diagnostics.

We entered the vehicle’s registration number, and it returned the exact model information. We entered the fault codes, starting with the P0322 rpm signal error. The bulletin returned with a list of known codes, and it included all the ones from our Audi.

This Audi Q5 has a well known EGR fault. When moisture enters the electronics of the EGR Valve, corrosion occurs. Then the corrosion causes electrical faults and starts triggering codes and running problems.

We removed the EGR valve top cover to investigate, and found corrosion. We cleaned off the corrosion to retest, but the obvious damage to the internal spring warranted a new valve to be fitted.

After disconnecting the EGR, most codes cleared successfully. After cleaning the corrosion from the electronics and reconnecting the EGR, most of the codes cleared successfully. Only the EGR disconnected codes returned, and the idle settled down after closing the EGR valve manually.

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