UK-POLOS.NET - THE VW Polo Forum

What's this error log thingy in the ecu and what kind of problems can it cause?

I think you're talking about fault codes? the ECU stores these when a sensor fails somewhere.

certain faults or too many of them will cause the ECU to go into "limp-home" mode where the fuelling goes really rich & the ECU stops using some of the sensor readings. this will allow you to get home or to a garage to get things sorted out but performance will be stupid & you'll be using tons of fuel.

so the fault codes themselves arent the problem, you get it hooked up to a fault code reader to see whats wrong, replace the offending sensor(s) & normally reset the ECU by leaving it unplugged for 1/2 an hour or so.

can you get one of these fault code readers or can you wire one up?

its apparently quite easy if you've got a few bits of wire, an led or bulb, a switch, the appropriate resistor (for the light), a soldering iron and the guts to carry it through
(alternatively a buzzer in place of the light)
i think it's 3 wires in the connector, both the switch and the light connect to one of them, but their other ends go to different connections.

i have no circuit plans to give you unfortunately, i've seen one out there somewhere and intend making my own one day..... when the ECU eventually goes wrong... dont want to wreck a good one!

it works by you pressing the switch, and it makes a series of flashes (or beeps) which signify different codes you can read off a list (also not available probably found in the same place as the circuit). after each code you press the button again until it gives you the "no more errors" code, at which point you either disconnect, or press again to start over.. (they're four groups of numbers from 1 to 4, so basically its a very slow, but human-compatible way of relaying an 8-bit value with 256 possible codes... it might go flash-flash-flash, pause, flash, pause, flash-flash, pause, flash-flash-flash-flash...... which is 3-1-2-4, whatever that error means)

Alas that only works on digifant-ed golfs. Made one of these, it just doesnt work on a polo. Theres a spare wire that needs to be conected to something and this setup simply doesnt account for it.

yeah unfortunately that DIY code reader wont read faults from a Polo Digifant ECU.

you'll need to either take it into a VW specialist (or any garage with VW fault code reading equipment) or buy/borrow a VAG-COM program & plug into it.