I'll apologise at the start for being vague but I only get to see this car for about 45mins at a time!

Came in with MIL on and codes for DPF sensor and EGR value. Found EGR unplugged - cleaned connections and refitted plug, ordered DPF sensor - live data showed constant reading of 106mB - and sent customer away.

Back in today, fitted new senor (superceded part no.) and live data showed either 0 or 106mB. Also had sensor code (sorry printer wasn't online). As new sensor was different, thought I'd connect the pipes the other way around. I now get live data reading in multiples of 21mB (42, 63 etc.) but code cleared ok. That's when I plugged in GScan just to see if it was a software bug - data just the same.

In the meantime, the EGR has been surging like crazy when driving at low speed. I've now unplugged it again and car drives fine with no codes at the moment.

Just to add into the mix, when the EGR was plugged in, I intermittently got errors U1118 and U2001. These clear happily when unplugged.

Do these symptoms ring any bells with anyone? I realise I'm going to have to get it back in for longer but not sure where to look next. I need to know the correct connections for the DPF sensor pipes as a start but any other pearls of wisdom would be great.