P0323

P0323 means the Ignition/Distributor Engine Speed Input Circuit is signaling intermittently — the PCM is losing the pickup-coil reference pulse from inside the distributor (or from an externally mounted pickup on some platforms) just long enough to drop spark and fuel, but the signal returns before the engine stalls. Cheapest-first ladder: scan live data while wiggling the distributor harness with the engine running and watch RPM for momentary drops to zero or huge spikes — a healthy distributor pickup-coil 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, while a Hall-effect pickup produces a clean 0 to 5 V square wave with rising/falling edges sharper than 1 microsecond. Backprobe the pickup signal wire at the PCM connector with a scope: dropouts, jagged edges, or a ground offset above 0.2 V are the smoking gun. Resistance-check the pickup coil itself — most VR pickups read 500 to 1,500 ohms between the two signal pins; open or shorted is dead. Inspect the distributor cap for carbon tracking inside, the rotor tip for corrosion, and the pickup wiring where it exits the distributor (heat cycles crack the insulation at the strain-relief grommet). Expensive misdiagnosis caveat: on GM Vortec 4.3/5.0/5.7 trucks the OptiSpark and later HEI/CMFI distributors are notorious for the optical-pickup or magnetic-pickup module failing intermittently — shops replace the entire $250-$500 distributor when reseating the 3-wire pickup connector and cleaning the corrosion at the cap pins clears the code; always pop the cap and inspect the pickup harness pigtail before condemning the distributor assembly.

Vehicle-specific patterns: 1996-2002 GM Vortec 4.3/5.0/5.7L (Silverado, Tahoe, Suburban, S-10) with the distributor-based ignition is the most common P0323 vehicle in the field — the OptiSpark on LT1 cars and the conventional distributor on Vortec trucks both fail at the optical or magnetic pickup, and water intrusion through the distributor vent is a known killer. 1997-2003 Ford 4.6/5.4L Modular V8 (F-150, Expedition, Crown Vic) with the early distributor-fed systems throws P0323 from cracked PIP sensor wiring inside the distributor housing. 1995-2004 Toyota 2RZ-FE / 3RZ-FE 4-cylinder (Tacoma, T100, 4Runner) and the 5VZ-FE V6 with distributor ignition throws P0323 from internal pickup-coil shorts and from corroded distributor cap terminals, especially on coastal trucks. 1996-2001 Jeep 4.0L inline-6 with the distributor-mounted CMP throws P0323 from a worn distributor shaft bushing letting the pickup gap drift out of spec. Estimated repair: $80 to $650.