P0545

P0545 sets when the ECU detects a 'circuit low' fault on the exhaust gas temperature (EGT) sensor 1 on bank 1 - the EGT sensor monitors exhaust gas temperature ahead of the catalytic converter or DPF (on diesels) and is used for emissions strategies including catalyst protection (cutting fuel when EGT exceeds catalyst melting threshold) and active regeneration trigger logic on DPF-equipped diesels. P0545 specifically is the low-side electrical fault. Cheapest-first ladder: (1) Locate the EGT sensor - threaded into the exhaust manifold or downpipe ahead of the cat, with a 2-pin connector and a thermocouple-style construction. (2) Disconnect the sensor and DMM the signal wire to ground with KOEO - stuck-low with the sensor unplugged confirms a harness short to ground; floating with the sensor unplugged means the sensor is the failure. (3) Check the sensor connector for heat damage - EGT sensors live in some of the hottest under-hood real estate and connectors melt. (4) Confirm the sensor itself isn't physically damaged - cracked thermocouple sheaths can short to the exhaust pipe (ground) and produce exactly this code. Expensive-misdiagnosis trap: a stuck-low EGT signal disabling DPF regen on a diesel and eventually clogging the DPF - the fix shifts from $90 (sensor) to $1,500+ (forced DPF regen or replacement).

Vehicle-specific patterns: 2011-2016 Ford F-250/F-350 with the 6.7L Power Stroke diesel throws P0545 from a melted EGT-1 connector at the turbo outlet. 2009-2014 Dodge RAM 2500/3500 with the 6.7L Cummins throws P0545 commonly from sensor failure after high-mileage service. 2013-2018 Chevy/GMC 2500HD with the 6.6L Duramax LML/L5P throws P0545 from chafed EGT harness near the turbo. 2014-2018 RAM 1500 EcoDiesel 3.0L throws P0545 from a known supplier-quality EGT sensor failure. Estimated repair: $90 to $1,500