P0562 fault code showing on diagnostics machine

[Ian Morgan]

I have a 2009 A3 2 litre TDI. Fault code P0562 (low voltage) was showing up on my diagnostics machine . The engine management light illuminated 2 days ago. I took the car to a tried and trusted garage who confirmed my fault code finding. they tested the voltage on the battery and it was showing 13.4, it should be between 14.2 and 14.4. The main issue with this fault code is the alternator so I told them to fit a new one which they did. The engine management light is still on . I have tried to clear the light with my OBD tool but it keeps coming back on. i have checked the voltage on the battery and its perfect. Ive taken the car for a fast runout today , the lights still on.
Has anyone came across this before and if so, what was the outcome?

[malt56]

Hi - not sure if this will help , I bought VCDS software which interrogates all the ECU areas in the car, (Engine,ABS etc) To my knowledge the OBD tool does not access all the ECU's therefore cannot clear the fault in those ECU's , the VCDS tool, however allows these to be cleared. In saying this, I have also found out that each ECU has a reset counter associated with each fault ,which after a pre-determined number of drive cycles appears to cause an auto reset of the code if the cause was fixed - so the light may go off eventually after numerous stop/start drive cycles - otherwise see if the garage can clear all faults from the ECU's.

[Ian Morgan]

malt56, thanks for your reply. Taking the car to an auto electrician on tuesday. Will see what he says. I plugged in my diagnostics machine yesterday, light was still on. With the engine running i turned off the light using the obd tool. i kept the engine running and took car for a drive, the light stayed off. I got home turned the ignition off then turned it back on and the light came back on. Not happy.
Thanks again for the reply.

[malt56]

I think all the ECU's for the various sections of the car can combine to light the engine light and that engine ECU may indeed log what the fault was caused by - BUT I think there is a original copy of the fault stored in with ECU related to the battery and its this one that needs to be cleared ( to my knowledge standard OBD diagnostics only clear the code from main (engine) ECU but does not clear the battery ECU - so everytime the car starts there will be a self check and I suspect the local fault code is being recopied to main ECU and thus putting engine light on again. VCDS software can access all ECU's and truly clear any faults logged within each ECU - anyway auto guy should be able to resolve either way

[Ian Morgan]

thanks malt56...you know your stuff. Hopefully there will be a positive outcome on tuesday.