P0372

P0372 means the Timing Reference High-Resolution Signal A is reporting too few pulses per crank revolution — the PCM expected the full count from the high-resolution reference wheel (typically 58 teeth seen per crank revolution on a 60-2 missing-tooth wheel, or 24 pulses on a 24X system) and is counting fewer than that. This is the inverse failure of P0371: missing pulses rather than extra ones. Causes are CKP sensor air gap too wide (sensor too far from the wheel to fully resolve each tooth), trigger wheel missing teeth (mechanical damage, broken tab, weld failure), failing CKP sensor losing amplitude on some teeth, a high-resistance signal wire dropping pulse amplitude below the PCM's detection threshold, or an open circuit cutting out groups of pulses. Cheapest-first ladder: backprobe the CKP signal wire at the PCM with a scope and crank the engine — a healthy 60-2 VR signal should produce 58 visible teeth and 2 missing per revolution at 0.5 to 1.5 V AC peak-to-peak cranking amplitude, rising to 5 to 12 V at 2,000 RPM; a Hall sensor produces a 0 to 5 V square wave. Pulses that disappear at idle but return at higher RPM mean weak signal coupling (air gap too wide or partial sensor failure). Pulses dropped at a specific rotational position mean a missing or damaged tooth on the trigger wheel. Resistance-check the signal wire end-to-end (under 1 ohm) and verify the sensor ground voltage drop is under 0.1 V. Check the CKP air gap with feeler gauges (FSM spec, typically 0.030 to 0.050 inches). Expensive misdiagnosis caveat: on Ford 4.6L/5.4L and GM trucks, P0372 after a harmonic balancer replacement is almost always the new balancer's reluctor ring sitting at a different axial position than the original, requiring a PCM relearn (Ford uses a Profile Ignition Pickup relearn procedure; GM requires a CKP variation relearn) — replacing the CKP sensor without performing the relearn does not clear the code.

Vehicle-specific patterns: 1996-2002 GM Vortec early-LS systems with 24X reference (LS1 Camaro/Corvette/Firebird) throw P0372 from a worn 24X reluctor wheel where teeth have eroded enough to drop below the sensor's detection threshold. 1999-2008 Ford 4.6L/5.4L Modular V8 (F-150, Expedition, Mustang GT, Crown Vic) is the textbook P0372 vehicle after balancer replacement — the new balancer's PIP ring sits slightly differently and the PCM cannot match the expected pulse train until the Profile Ignition Pickup relearn is performed with an OEM-capable scan tool. 2005-2012 Chrysler/Dodge 5.7L Hemi (Ram, Charger, 300) throws P0372 from CKP sensor failure where one or two teeth drop out as the sensor heat-soaks. 2007-2014 Nissan VQ35DE/VQ37VHR (Altima, Maxima, 370Z) throws P0372 from a damaged reluctor on the flywheel after improper clutch or flexplate service. Estimated repair: $200 to $1,400.