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Matt, Mechanical Engineer
Category: Volkswagen
Satisfied Customers: 22931
Experience:  BEng hons Mech engineering, in auto industry 22 years
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2006 VW Polo 9N 1.4 BUD engine My wife tried to start it

Customer Question

2006 VW Polo 9N 1.4 BUD engineMy wife tried to start it after work last night, completely dead. Eventually got it jump started and did manage to drive home, however ABS warning light remained lit along with the red brake warning light next to it, as soon as she started driving the power steering stopped working and the warning light for that lit.I had a quick look with a generic OBD reader this morning and got code P0686.I have replaced the battery, and cleared the ABS & PAS issues.The car drives fine.I seem to be getting a 0.15A current draw when the car is dormant, which leads me to suspect that the ECM relay is faulty as the initial OBD fault suggested. I would like to check this relay but cannot find it!
Submitted: 11 months ago.
Category: Volkswagen
Expert:  Matt replied 11 months ago.



as you have probably checked yourself that code shows there's an issue with the ECU power relay or a defective ignition switch

its worthwhile just checking main battery connections at either end for tightness and corrosion and also check that the battery voltage is OK ( at least 12.5V with ignition on) as its quite possible the battery has died as this too can create this issue

Also check that the alternator is actually charging the battery in the car by taking a battery voltage reading with the engine off then another with the engine running. The 2nd reading should be higher than the 1st and climbing steadily. And also check that the alternator is secure to the engine as this provides the ground for the charging circuit and make sure that the engine / gearbox earth strap is secure and the contacts are clean and bright.

if the alternator appears not to be working - take it to a electrical specialist and ask them to test it as sometimes you can replace just the diode pack and this will repair the alternator without requiring replacement

If this is all OK then I'd consider replacing the ECU power relay which is no.3 on the panel inside the car ( see image)

Customer: replied 11 months ago.
Relay location 3 is empty....
Expert:  Matt replied 11 months ago.


is there any power to the sockets of the no.3 relay with the ignition on?

If not then check the alternative location relay 10

see image

Customer: replied 11 months ago.
10 is also empty......
Expert:  Matt replied 11 months ago.

Ok in that case I'll opt out and open this up to others