The crankshaft position variation relearn procedure, often referred to as CASE (Crankshaft Angle Sensor Error), CPK (Crankshaft Position Known), or CVL (Crankshaft Variation Learn), is crucial for optimal engine performance in Chevy vehicles. This procedure allows the Powertrain Control Module (PCM) to compensate for minor manufacturing variations in the crankshaft, reluctor rings, and crankshaft position sensor. This precise calibration enables the PCM to accurately detect misfires across a broader range of engine speeds and loads. But can you perform this procedure without a scan tool? Let’s explore.
Understanding the Chevy Crank Variation Relearn Process
The PCM stores learned crankshaft position system variation values in its non-volatile memory. These values become the baseline for comparison. When the PCM detects significant deviations from these stored values, it triggers the Diagnostic Trouble Code (DTC) P1336, often indicating the need for a relearn.
Several situations necessitate a crank variation relearn:
- PCM Replacement: Installing a new or different PCM requires a relearn as the new unit lacks the specific variation data for your engine.
- Engine Replacement: A new engine will have different tolerances, requiring a relearn.
- Crankshaft or Crankshaft Position Sensor Replacement: These components directly impact the variation readings.
- Harmonic Balancer Disturbances: Any repair affecting the relationship between the crankshaft, harmonic balancer, and crankshaft position sensor necessitates a relearn.
Importantly, reflashing your existing PCM with new code does not require a relearn. The variation data resides in non-volatile memory, unaffected by code updates.
Can You Bypass the Scan Tool for a Chevy Crank Variation Relearn?
Unfortunately, no known method exists to perform a Chevy crank variation relearn without a compatible scan tool. The procedure requires specialized equipment to communicate with the PCM and input the necessary data. The system cannot self-learn these variations through driving or other procedures.
While some speculate about workarounds, these methods are unreliable and often unsuccessful. Attempting these could lead to further diagnostic trouble codes or performance issues.
What Scan Tools Can Perform a Chevy Crank Variation Relearn?
Several professional-grade scan tools can execute this procedure:
- GM Tech II: The factory scan tool used by GM dealerships. However, finding a technician proficient in its use for this specific procedure might be challenging.
- Snap-on MT2000 and MT2500: These high-end scan tools offer the functionality (often referred to as CPK learn).
- HP Tuners: This software offers CASE Learn capabilities, but user feedback suggests inconsistencies in its effectiveness.
Working with a GM Dealership for a Crank Variation Relearn
If opting for a dealership, clearly communicate your needs. Referencing the diagnostic procedure for DTC P1336 in their service information system (e.g. DealerWorld) and specifically mentioning the variation learn steps after a “hypothetical” PCM replacement can help ensure they understand the required procedure. Crucially, emphasize avoiding PCM programming before the relearn to prevent overwriting any existing aftermarket tuning.
Understanding the intricacies of the Chevy crank variation relearn process is vital. While a scan tool is indispensable for this procedure, knowing the why and when empowers you to make informed decisions regarding your vehicle’s maintenance and repair. Consult a qualified technician with the appropriate scan tool to ensure accurate and successful completion of the relearn procedure.
