BMW fault code 421C
Engine electronics
In the engine electronics, code 421C means different things depending on the version of the module in the car. Find your car below; the app shows the right one for yours.
421C NOx sensor after DeNOx catalyst, plausibility lambda
Module versions: Digital Diesel Electronics (D72N47B0), Digital Diesel Electronics (D73N47A0)
Which BMWs have these versions depends on the engine and equipment, so we don't list them here; AutoLingo for BMW reads which version your car has.
421C NOx sensor after DeNOx catalytic converter, plausibility lambda
Module version: Digital Diesel Electronics (D73N57D0)
Which BMWs have this version depends on the engine and equipment, so we don't list them here; AutoLingo for BMW reads which version your car has.
Reading and clearing it
Fault code 421C is a BMW code, stored in the car's engine electronics, not a generic OBD2 code (P0xxx): a generic OBD2 reader only reaches the engine's emissions faults, so it won't show it. AutoLingo for BMW reads it with BMW's own diagnostic protocols, in plain English, with the details the module stored about it, and clears it after a repair. If a fault comes right back after it's cleared, the problem is still there.
The engine electronics is on: 3 Series (E46), Z8 (E52), X5 (E53), 5 Series (E60), 5 Series (E61), 6 Series (E63), 6 Series (E64), 7 Series (E65), 7 Series (E66), 7 Series (E67), X5 (E70), X6 (E71), X6 (E72), 1 Series (E81), 1 Series (E82), X3 (E83), X1 (E84), Z4 (E85), Z4 (E86), 1 Series (E87), 1 Series (E88), Z4 (E89), 3 Series (E90), 3 Series (E91), 3 Series (E92), 3 Series (E93)
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