Caterpillar® 320D Crankshaft Position Sensor — Stable Sync. Clean Starts. Predictable Power.

When a 320D hesitates after a hot refuel, idles with a light "hunt," or throws erratic timing codes, the culprit is often the crankshaft position sensor (CKP). This hall-effect speed/timing sensor reads the tone wheel on the C6.4 engine and gives the ECM the zero-latency reference it needs to schedule injection and hydraulic load sharing. In dealer and aftermarket catalogs for the 320D family, this sensor is widely listed under P/N 238-0120 (often written 2380120) for 312D/320D/320E/324E/450E applications; several sources also note legacy/related callouts such as 311-3857 in replacement lists.

 

Rail pressure meets target faster. With a clean CKP signal, the ECM stabilizes pilot→main events quickly after crank-shortening hot starts and reducing starter wear.

Cleaner tip-in, fewer smoke puffs. Sharper crank phase information means injection angle isn't "late," which trims the grey haze operators notice when loading the boom.

Error-free synchronization. A drifting or noisy CKP causes timing fallback or stall-on-sync; a fresh sensor restores crisp RPM tracking for work modes and auto-idle.
Field listings specifically identify the 238-0120 as the crankshaft/speed sensor for C6.4-powered 320D machines and sister models, underscoring its role in start/idle quality.

 

 

Primary part number: 238-0120 (CKP / speed sensor). 

Common replacements cited: 311-3857 appears in multiple "replaces" lists for the same 320D/C6.4 fitment. FridayParts

Platforms frequently listed: CAT 312D, 320D, 320E, 324E, 450E with C6.4 engine.

You may also see "timing/speed sensor" pages for the 320D referencing other numbers (e.g., 245-4630 for different engines). Match the exact code on your removed sensor and your EPC before ordering

 

 

Type: Hall-effect magnetic speed/position sensor (2-wire/3-wire styles vary by kit). Many listings explicitly describe it as a "hall effect speed sensor."

Function: Measures crank speed and tooth edge timing for ECM synchronization of injection and idle control. 

Supply form: Single sensor, sealed connector, O-ringed body; sold as new replacement with warranty by multiple vendors

Noted compatibility text in market listings: "C6.4 / 320D" and "crankshaft position/speed sensor 238-0120

 

 

Confirm the fault: Graph RPM during crank; look for dropouts or a "saw-tooth" phase trace. If cam signal is good and crank is noisy, replace CKP.

Inspect the tone wheel gap: Excess metallic debris or a bent tooth mimics sensor failure; clean and set gap per the engine manual.

Swap sensor & seal: Lightly oil the O-ring; avoid twisting the harness. Torque to spec; do not shim unless the manual instructs.

Commissioning: Clear codes, perform a hot-restart test, and verify idle stability and target rail pressure tracking.
These steps mirror guidance implied by supplier fitment pages and standard C6.4 diagnostic practice for speed/phase faults.

 

 

Faster hot starts - no more long crank after heat-soak.

Stable idle - ECM stops "chasing" phase, so work modes engage cleanly.

Crisp throttle response - injection timing lands on target, reducing tip-in haze.

 

 

"Caterpillar 320D crankshaft position sensor 238-0120"

"C6.4 engine speed/timing sensor CKP"

"Replaces 311-3857 for CAT 320D"
These mirror how reputable marketplaces title the part and match search behavior for 320D owners

 

 

If your 320D (C6.4) shows slow hot starts, hunting idle, or speed/phase faults, a genuine-spec crankshaft position sensor (238-0120) is the small part that delivers a big fix. It restores the ECM's timing reference so injection, idle, and work modes feel "factory" again-keeping your machine productive and predictable. Cross-check your removed sensor's code and engine tag to confirm this exact number before purchase.

 

 

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