P0201

P0201 isolates the fault to the cylinder 1 injector driver circuit specifically, meaning the PCM commanded that injector on and either saw no current flow (open circuit), excessive current (shorted coil), or a driver-side fault on that one pin, while the other cylinders report normal. Cheapest-first ladder: swap the cylinder 1 injector with cylinder 3 or 4 and clear codes, drive the car, and see if the code follows the injector (confirms injector failure) or stays on cylinder 1 (confirms wiring or PCM driver); measure resistance at the cylinder 1 injector itself, which for port-fuel applications should be 11 to 17 ohms and within 0.5 ohm of the other cylinders, and for GDI direct-injection applications should be 1 to 3 ohms; check the connector for green corrosion or backed-out terminals and verify the 12V feed at the injector connector reads battery voltage key-on. A scan tool injector balance test should show cylinder 1 pulse-width matching the others within 0.2 ms at idle (typically 2.5 to 3.2 ms warm) before you condemn the injector. The expensive misdiagnosis is replacing the cylinder 1 injector ($180 to $450 on GDI engines after labor) when the real failure is a backed-out terminal in the connector or a broken pin inside the PCM that needs a $900 module rather than a $200 injector.

Vehicle-specific patterns: 2006-2013 BMW N54/N55 335i and 535i throw P0201 routinely after injector replacement when the new injector's six-digit index code is not coded into the DME via ISTA (BMW SIB 13 01 13 mandates index coding to match flow rate, uncoded injectors cause balance faults on cylinder 1 first because it is closest to the rail inlet); 2011-2019 Ford 3.5L EcoBoost F-150 throws P0201 from carbon-tip fouling on cylinder 1 because the front cylinder runs leanest under boost, and a walnut-shell intake-valve cleaning plus injector replacement is typical at 80k to 100k miles; 2008-2014 VW/Audi 2.0T (EA888) trips P0201 when the high-pressure direct injector's solenoid coil opens, often after extended ethanol exposure; 2003-2008 Honda Accord 2.4L K24 sees P0201 from a clogged port injector after years on ethanol-blend fuel, cleanable with a Motorvac service. Estimated repair: $80 to $850.