I have a 2007 Grand C4 Picasso Exec. 1.6 HDi. I get an intermittent fault flash up on startup telling me that there is a parking brake problem. I have just changed the brake light switch and still have the fault. The switch is still on the left on a LHD and that panel is a real cow to remove! Any ideas as to what else it can be please? Wed Jan 30 2013, 04:41am. Member No: #82. Joined: Jan 22 2007. Location: Hoylake. U1109: CAN data bus, transmission control system - no communication, invalid or missing data. However, I suggest you find a garage with Citroën's diagnostic equipment - it's possible your local garage was unable to read the fault code. Hello all, I have only just bought a CITROEN C4 SX 1.6 auto. While driving my car in 3rd it changes to 4th dries fine for a little while then it changes to limp mode which is 3rd gear. Citroen Penzance carried out diagnostic tests to the gearbox, it showed fault code p0006 pressure regulation reading permanent fault in BVA-AL4 auto box. 3 days ago · If you experience any issues with the gearbox of your Citroen Grand C4 Picasso, it is important to have it inspected by a qualified mechanic as soon as possible to avoid further damage and ensure your safety on the road. 4. Common Problems Across Both Generations 4.1. Fuel Consumption Issues 4.1.1. Poor fuel economy on diesel engines TG0oYr.