OBD-II Code P0315 — What It Means & How to Fix It

What Does This Error Mean?

P0315 means the PCM has not learned the variation pattern of the crankshaft position sensor reluctor wheel. This calibration is needed to accurately detect misfires. Without it, the misfire detection system cannot work properly. This code is most common after replacing the crankshaft sensor, PCM, or crankshaft itself.

Affected Models

Common in GM vehicles requiring a Crankshaft Position Variation Learn (CASE learn) procedure
Common in GM trucks with LS-series V8 engines
Common in GM cars with 3.8L V6 engines
Common in Chevrolet and GMC SUVs after PCM replacement or reprogramming
Also seen in some Ford and Chrysler vehicles after sensor or PCM replacement

Common Causes

Crankshaft position variation learn procedure was not performed after sensor replacement
PCM was replaced or reprogrammed and lost the stored calibration data
Crankshaft or reluctor wheel was replaced without performing the relearn
Battery was disconnected on some vehicles that require periodic relearn
Faulty crankshaft position sensor producing inconsistent signals preventing the learn

How to Fix It

Understand what P0315 means before replacing parts. This code almost always appears because the crankshaft position variation learn procedure was not performed. It does not necessarily mean any hardware is broken.

If you recently replaced the crankshaft sensor, PCM, or had engine work done, skip ahead to the relearn procedure step immediately.
Check the crankshaft position sensor and its wiring. Look for obvious damage, corrosion at the connector, or a sensor that is loose in its mounting boss. A faulty sensor can prevent the relearn from completing successfully.

The relearn will fail if the sensor signal is noisy or intermittent. Confirm the sensor is good before attempting the procedure.
On GM vehicles, perform the Crankshaft Position System Variation Learn procedure using a capable scan tool. This requires the engine to reach operating temperature. The procedure then commands a specific throttle blip sequence with the scan tool monitoring the crank signal.

This procedure cannot be done with a basic code reader. It requires a bidirectional scan tool such as a Tech 2, GM MDI, Autel, or similar professional tool.
After completing the relearn procedure, clear all stored fault codes. Start the engine and let it idle. Drive the vehicle normally. Confirm that P0315 does not return and that no misfire codes are present.

If P0315 returns after a successful relearn, the crankshaft position sensor or reluctor ring may have an actual fault that is preventing the system from storing calibration data.
Replace the crankshaft position sensor if it cannot pass the relearn procedure. After replacement, perform the variation learn procedure again. A new sensor must always be calibrated before the PCM will accept its data for misfire detection.

Always use a quality crankshaft sensor. Cheap aftermarket sensors sometimes fail the relearn due to poor signal quality.

When to Call a Professional

On GM vehicles, the CASE relearn procedure requires a capable scan tool. Basic OBD-II readers cannot perform this procedure — it needs a professional-grade scanner or a dealer tool. A shop can perform the relearn in under 30 minutes. Cost is typically $80-$120 for the procedure alone. If the sensor itself is bad, add the cost of sensor replacement.

Frequently Asked Questions

Do I need a special tool to fix P0315?

Yes, in most cases. The crankshaft position variation learn requires a bidirectional scan tool. A basic code reader can read P0315, but cannot perform the relearn. Options include a professional shop visit, a dealer, or purchasing a capable scan tool. Some professional scan tools like Autel or Launch can do this procedure.

Can P0315 cause misfires or rough idle?

Indirectly, yes. Without a completed variation learn, the PCM's misfire detection is less accurate. The engine may set false misfire codes or miss real misfires. Actual driveability problems are rare from P0315 alone. But if you also have misfire codes, the unlearned variation may be masking the true cause.

Why does P0315 appear after a battery replacement?

On some GM vehicles, the PCM stores the variation learn data in volatile memory. A battery disconnect can erase this data on older models. Modern vehicles typically store this in non-volatile memory and do not require relearning after a battery swap. If it happens on your vehicle, a relearn procedure is the fix.