02/09/2026
2012 focus 1.0 in for a wetbelt change, but had a P420 catb efficiency code. Live data showing oxygen sensors are ok, removed the post cat sensor, inspected the cat converter for signs of damage, all ok, smoke test revealed a leaking Camshaft cover.
Looks previously broken in 2 places from a service elsewhere. This will bring an efficiency code on. Also inspected the brake vacuum pump, all ok, but the valve in the end of it, broken. £6 part fix.
The 3 C's.
Complaint ✅...Engine Light On
Cause ✅..... Camshaft Cover
Correction ✅.... Retest For Leaks.