splin

Hi,re Our 2011 Fabia Greenline II 1.2TDI just started behaving erratically - fortunately my wife was close to home and just got back. It starts up OK but then usually runs with sudden very short dips in revs usually accompanied by a harse knock (a bit like pinking) randomly every few seconds. It happens at different engine speeds. Initially there were a few fault codes P2452 P0401, P060C, P0641,and pending faults P2015, P046C Other odd symptoms were once after starting the engine the engine idled, but the rev counter went to maximum and stayed there. Another time it started but the starter motor continued running. Occasionally it would idle but there was no response to the throttle. I went through a few cycles of resetting the codes and turning the ignition on and rescanning. Sometimes no codes came back and other times several pending faults usually one of those listed above (I can't remember exactly). At one point P0641 (5V sensor reference A open) and P060C were coming on as active faults, the latter being the most worrying. I only have a cheap ALDI code reader so I'll try to borrow a good one from a mechanic I know to seee if it gives some more info, but I'm not sure what to look for. I started removing sensor connectors on the engine; 5V was present on them all and seemed solid when the engine was running - but I was using a slow DVM so I might try monitoring with an oscilloscope to see if there are any short dropouts. Since then P060 hasn't recurred but P0641 does. In case a faulty sensor was briefly shorting the 5V, I tried removing all the connectors on the engine that still allowed the engine to run (DP pressure, EGR pressure, EGR valve etc.) It made no difference to the erratic running. I'm wondering if the crank position sensor may be faulty - it could account for the sharp knocks if it injects at the wrong time, but there aren't any associated fault codes. I hope it isn't the ECU, but its a concern given the odd range of fault codes. Last few times I tried I'm got a P2245 - turbo wastegate solenoid a low? However I guess that if something is intermittently dragging the reference down then the ECU could detect it on any of the sensors. Any ideas? would it be worth replacing the crank position sensor anyway given it doesn't seem expensive at around £10? With code P0641, should there always be another fault code indicating which sensor it got a bad reading?