P0371

P0371 means the Timing Reference High-Resolution Signal A is reporting too many pulses per crank revolution — the PCM expected a specific number of edges from the high-resolution crank or cam reference (typically 58 teeth on a 60-2 missing-tooth wheel, or 24 evenly-spaced pulses on GM's 24X reference wheel) and is counting more than that. This is a signal-integrity problem: electrical noise inducing phantom pulses on the signal wire, a damaged trigger wheel with an extra burr or weld bead, a CKP sensor reading too close to the wheel and picking up trailing-edge bounce, or wiring routed too close to a high-current load (injector harness, ignition coil primary, alternator). Cheapest-first ladder: scan live data and capture the freeze-frame RPM and engine load when the code set — phantom-pulse counts at idle point at noise pickup; counts under WOT point at mechanical resonance or trigger-wheel damage. Backprobe the CKP signal wire at the PCM with a scope: a healthy 60-2 VR signal cranks at 0.5 to 1.5 V AC peak-to-peak and rises to 5 to 12 V AC at 2,000 RPM with two clearly visible missing teeth per revolution; a Hall-effect sensor produces a 0 to 5 V square wave with sharp edges. Extra pulses appearing between expected teeth = noise or mechanical damage. Inspect the trigger wheel visually for added material, burrs, weld spatter, or a cracked/loose wheel. Verify CKP sensor air gap (typically 0.030 to 0.050 inches, FSM-specific). Check signal-wire shielding and routing — bundled with injector wiring is a frequent culprit. Expensive misdiagnosis caveat: on GM Vortec early-LS systems with the 24X reference, P0371 immediately after a harmonic balancer or front timing cover replacement is almost always a damaged trigger wheel or a misaligned CKP sensor — pull the front cover and inspect before chasing wiring or PCM faults.

Vehicle-specific patterns: 1996-2002 GM Vortec early-LS systems with 24X reference (LS1 Camaro/Corvette/Firebird, LS6 Z06) throw P0371 from a damaged 24X reluctor wheel behind the harmonic balancer — the wheel cracks or loses a tooth and the PCM counts phantom edges. 1999-2007 Ford 4.6L/5.4L Modular V8 (F-150, Expedition, Mustang GT) throws P0371 after balancer or front-cover service when the technician disturbs the CKP sensor mounting and the gap drifts below spec, causing the sensor to pick up trailing-edge bounce. 2005-2010 Chrysler 2.7L/3.5L V6 (300, Charger, Pacifica) throws P0371 from a known TSB-style issue where the CKP signal wire chafes against the timing cover and picks up alternator noise. 2007-2012 Nissan VQ35DE (Altima, Maxima, 350Z) throws P0371 from a cracked reluctor ring on the back of the flywheel after a clutch or torque-converter job where the technician pried on the wrong tab. Estimated repair: $200 to $1,400.