OBD-II Diagnostic Trouble Code
P0315 — Crankshaft Position System Variation Not Learned
P0315 means the ECM has not learned the small manufacturing differences in the crankshaft tone wheel teeth (crankshaft variation or CKP relearn). Without this learn, the ECM cannot run misfire detection accurately. It usually sets after an ECM replacement or reprogramming, a crankshaft sensor change, or flywheel or crankshaft work.
Severity 3/5
Truck-relevant
Service this week
Severity
Service this week
Crankshaft Position System Variation Not Learned
Code
P0315
Category
Powertrain
Subsystem
Ignition
Truck-relevant
Yes
What this means for truckers
Service within a few days on a Cummins X15, Detroit DD15, PACCAR MX-13. Performance is likely degraded. Continuing to drive without service risks additional component damage.
Before you replace parts — try this first
P0315 on the Ignition system is most often crankshaft variation relearn not done after ecm replacement or reprogramming — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
Usually only a check-engine light, with the truck running normally. Misfire monitoring may be disabled, so the truck may not pass an emissions or readiness check. Some engines also show false misfire codes until the learn is done.
Common causes
- CommonCrankshaft variation relearn not done after ECM replacement or reprogramming ($80–$250)
- CommonRelearn started but not completed (wrong conditions, engine not warm, wrong procedure) ($80–$250)
- OccasionalCrankshaft position sensor, tone ring, flywheel or crankshaft replaced or damaged without a follow-up relearn ($150–$700)
- RareNoisy crankshaft sensor signal stopping the learn from finishing ($150–$500)
How to fix
Perform the crankshaft position variation relearn with a capable scan tool, following the OEM conditions (warm engine, specific rpm)
When to use: First and in most cases the only fix
Repair any other crank, cam or misfire codes first, then repeat the relearn
When to use: When the relearn will not finish
Scope the crankshaft sensor signal and inspect the tone ring for damage or debris
When to use: When the learn fails repeatedly
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → P0300 — Random/Multiple Cylinder Misfire Detected
- → P0301 — Cylinder 1 Misfire Detected
- → P0302 — Cylinder 2 Misfire Detected
- → P0303 — Cylinder 3 Misfire Detected
- → P0304 — Cylinder 4 Misfire Detected
Frequently Asked Questions
Can I drive with code P0315?
P0315 is severity 3 — plan service within a few days. Performance is likely degraded already (you may feel reduced power, harsher shifts, or slightly worse fuel economy). Continuing to drive risks additional damage to adjacent components.
How much does it cost to fix P0315 on a commercial truck?
Total repair cost ranges $80–$700 depending on the root cause. The cheapest fix is usually the first one listed below — Crankshaft variation relearn not done after ECM replacement or reprogramming — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will P0315 fail a DOT inspection?
P0315 is generally not a direct DOT inspection fail item by itself. Inspectors focus on safety-critical systems (brakes, steering, tires, lights, hours-of-service). However, the check engine light alone can trigger additional inspection scrutiny. Best practice: fix the code and clear it before a planned inspection.
What's the difference between P0315 and related codes?
P0315 is closely related to: P0300 (Random/Multiple Cylinder Misfire Detected), P0301 (Cylinder 1 Misfire Detected), P0302 (Cylinder 2 Misfire Detected), P0303 (Cylinder 3 Misfire Detected). These codes share the same subsystem (ignition) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only P0315 is set without the companions, the issue is more isolated.
How do I prevent P0315 from coming back after a repair?
For P0315 (Crankshaft Position System Variation Not Learned), prevention centers on the ignition system. Use OEM-spec injectors and spark plugs (gas). Address fuel quality issues immediately — bad fuel kills injectors. Cylinder balance test annually for early warning.