Performing a crank variation relearn, sometimes referred to as a CASE relearn, is a crucial procedure after certain automotive repairs or modifications. This process ensures your engine management system accurately reads crankshaft position, which is vital for optimal engine performance and preventing misfires. While this guide is initially based on experiences with EFILive, the principles and steps are highly applicable when using a BlueDriver OBD2 scanner. Here’s what you need to know to successfully complete a crank variation relearn using an OBD2 tool like BlueDriver.
Before you begin the crank variation relearn procedure with your BlueDriver OBD2 scanner, it’s imperative to ensure your vehicle meets specific preconditions. Failure to address these prerequisites will prevent the procedure from running correctly. Pay close attention to the following:
Essential Pre-Conditions:
-
Diagnostic Trouble Codes (DTCs): No Crankshaft Position (CKP) or Camshaft Position (CMP) sensor related DTCs, or other specific codes should be present. Specifically, ensure none of these codes are active: P0335, P0336, P0341, P0342, P0343, P0117, P0118, P1539, P1546, P0705, P0706, P1810, P1825. These codes indicate issues that must be resolved first as they directly interfere with the crank relearn process.
-
Engine Coolant Temperature (ECT): The engine coolant temperature must be within the range of 150°F to 220°F (65°C to 104°C). This temperature range is necessary for the engine to be in a stable operating condition for the relearn process.
-
Engine RPM: Ensure the engine RPM is below 2400 RPM before initiating the procedure. High RPMs can prevent the diagnostic tool from accurately starting the relearn process.
-
Throttle Position Sensor (TPS): The Throttle Position Sensor must read 0%, indicating a closed throttle position. This is crucial for the engine to respond correctly during the relearn steps.
-
Vehicle Speed Sensor (VSS): Vehicle speed must be 0 mph. The vehicle must be stationary with the VSS reading zero to proceed.
-
Parking Brake: Engage the parking brake firmly to ensure the vehicle remains stationary throughout the procedure, prioritizing safety.
-
Transmission Position: The transmission must be in Park (for automatic transmissions) or Neutral (for manual transmissions). This is a standard safety and procedural requirement for diagnostic processes.
-
Accessories Off: Turn off all unnecessary accessories such as air conditioning, headlights, and radio. This minimizes electrical load on the system during the procedure, ensuring stable readings.
-
Brake Pedal: Keep your foot firmly applied to the brake pedal throughout the initial setup and until instructed otherwise. This is another safety precaution.
Crank Variation Relearn Procedure with BlueDriver OBD2 (Adaptable from EFILive):
Once all the preconditions are met, you can proceed with the crank variation relearn process. While these steps are adapted from EFILive instructions, they are generally applicable to OBD2 scanners like BlueDriver, which offer similar diagnostic functionalities:
-
Connect BlueDriver Scanner: Connect your BlueDriver OBD2 scan tool to the vehicle’s OBD2 port and establish a connection using the BlueDriver app on your smartphone or tablet.
-
Navigate to Diagnostic Functions: Within the BlueDriver app, navigate to the diagnostic functions or control module section. Look for options like “Service Procedures,” “Special Functions,” or “Powertrain Control Module (PCM) Controls.”
-
Initiate Crank Variation Relearn: Locate and select the “Crank Variation Relearn,” “CKP Relearn,” or “CASE Relearn” function. The terminology might slightly vary depending on the BlueDriver software version.
-
Activate the Procedure: Follow the on-screen prompts to activate the relearn procedure. This might involve pressing an “Activate” or “Start” button within the app.
-
Increase RPM and Release Throttle: As prompted by the BlueDriver app, quickly depress the throttle pedal to increase the engine RPM above 4000 RPM within 10 seconds. Hold it momentarily at this RPM.
-
Listen for Stumble/Misfire: Pay close attention to the engine sound. You should hear or feel a slight stumble or misfire as the PCM learns the crank variation.
-
Release Throttle Immediately: The moment you detect the stumble or misfire, immediately release the throttle pedal.
-
Engine Spindown to Idle: Allow the engine RPM to naturally decrease and stabilize at idle speed.
-
Turn Off Engine and Wait: Once the engine has returned to idle, turn off the engine completely and wait for at least 15 seconds. This allows the PCM to finalize the learned data.
-
Deactivate Scanner (Optional): While waiting for 15 seconds, you can optionally use the BlueDriver app to deactivate the diagnostic procedure.
Completing the crank variation relearn procedure ensures the engine control module has accurately learned the minute variations in crankshaft position. This is essential for accurate misfire detection and overall engine management, especially after replacing components like the crankshaft position sensor, flywheel, or performing engine work. By following these steps with your BlueDriver OBD2 scanner, you can confidently perform this critical maintenance task.
