P0375

P0375 means the secondary high-resolution timing reference signal (Signal B input to the ECM/PCM) is malfunctioning in a way the controller can't otherwise classify as 'erratic' or 'no pulses' — typically a correlation failure between CKP-A and CKP-B, or a signal that's electrically present but doesn't match the expected pattern (wrong pulse count per revolution, phase offset, or amplitude). Cheapest-first ladder: (1) scan-tool both crank-position inputs simultaneously and look for the cam-to-crank correlation reading — a healthy system shows correlation within +/- 2 degrees crank; anything beyond that is mechanical (stretched chain, slipped reluctor) rather than electrical. (2) Scope CKP-A and CKP-B on a two-channel scope and verify the expected pulse-per-revolution count — missing-tooth detection on most domestic diesels is 58-of-60 teeth (two missing as the synchronization gap), while some VAG TDI applications use 35-of-36; a wheel that suddenly shows 56-of-60 has a chipped tooth. (3) Verify the air gap on the secondary sensor — 0.5 to 1.5 mm is typical; a sensor that's backed out 2 mm by a missing shim reads weak amplitude and triggers P0375. (4) Check for shared-ground faults — many engines route CKP-A and CKP-B grounds to the same PCM pin, and a poor ground there shifts the B signal threshold without affecting A. Expensive-misdiagnosis caveat: before you replace the CKP-B sensor, scope it AGAINST CKP-A — if A and B are both clean individually but the phase offset is wrong, the timing chain has stretched and the reluctor on the cam-end of the engine has slipped relative to the crank-end; a new sensor changes nothing and you need a timing-chain service.

Vehicle-specific patterns: 2008-2010 Ford 6.4L Powerstroke commonly throws P0375 from a known CKP-B sensor failure where the sensor's internal Hall element loses linearity at temperature — the truck starts cold and runs fine until oil temp climbs past 200 F, then sets the code and goes into reduced power. 2011-2016 GM Duramax LML throws P0375 when the camshaft reluctor on the rear of the camshaft loses its press-fit and rotates a few degrees; symptoms include hard hot-start and intermittent stall. 2007-2010 Mercedes OM642 (Sprinter, ML320 BlueTec) throws P0375 from a TSB-documented harness routing issue where the CKP-B pigtail rubs the bell-housing flange. 2008-2013 BMW N57 inline-6 diesel throws P0375 from a failing Bosch CKP that goes intermittent above 3,500 rpm only. Estimated repair: $200 to $1,400.