The secondary air pump reinstallation process was all straightforward and done without breaking anything metallic or plastic – always a good result! The battery was reconnected, error codes cleared, and a short engine run to see what progress had been made…

Fixing the air pump leak had cleared 4 of the codes with just P1114 and P1118 remaining linked with the B1 S2 Lambda sensor located mid-way down the exhaust on the 2nd CAT unit. This Bosch sensor had only been replaced 2 years before at a local garage so not impressed it had failed already.

The plastic shield highlighted above houses the connections for both Lambda sensors. On disconnecting the B1 S2 connector it was apparent the plug and socket had somehow filled with water and caused the error issue. Both the plug and socket were dried, bagged, and silica gel sachets overnight but this made for no improvement.

A replacement Lambda sensor was ordered in as well as an off-set socket adapter to help the removal and installation work. Access was just too tight on top of the exhaust for normal tools; another example of manufacturing design with an absence of foresight for regular servicing work. Some silicon grease was added to the new plug connector to discourage future water ingress. Everything was put back together and it is satisfying to report all error codes remain cleared and this Major Wobbly has been resolved. A good job!