Tech Tips: FLASH Reprogramming – GM Crankshaft Variation Relearn Procedure – UnderhoodService

Tech Tips: FLASH Reprogramming – GM Crankshaft Variation Relearn Procedure

A Crankshaft Variation Relearn Procedure must be performed if on 1996 and newer GM vehicles if: the ECC was reprogrammed; the crankshaft position sensor has been replaced; or the ECC has been replaced.

GM Crankshaft Variation Relearn

All 1996 and newer GM vehicles with FLASH reprogramming ECCs.

Crankshaft Variation Relearn Procedure must be performed if:
• ECC was reprogrammed.
• Crankshaft position sensor has been replaced.
• ECC has been replaced.

Follow the relearn procedure outlined below:

1. Install the scan tool on the Data Link Connector (DLC) located under the dash. Apply the parking brake and block wheels. Ensure the hood is closed.

2. Place the transmission in park for automatics and neutral for manual transmissions.

3. Start the engine and bring it up to operating temperature.

4. Apply the hydraulic brakes. Select and Enable Crankshaft Variation Relearn Procedure using a scan tool.

Caution: Release the throttle to idle position once the CKP fuel cut off is activated and the engine starts to decelerate.

5. Slowly accelerate the engine to 4,000 rpm (or indicated rpm for your vehicle). Hold rpm until the engine speed drops back toward idle.

Release the throttle immediately once procedure is learned! Once the variation values are learned, the ECC will return engine control to the driver. The scan tool should indicate a successful relearn.

6. Turn off the engine for at least 15 seconds and remove the scan tool. If the relearn procedure was not learned, DTC P1336 will be stored in the memory.

7. If present, ensure that the CKP procedure was followed carefully.

Perform test procedures and repair as necessary.

Note: Refer to the vehicle’s service manual for detailed relearn procedures specific to your application, and also to your scan tool’s operating procedure.

Courtesy of CARDONE Industries, Inc.

You May Also Like

Diagnosing Intercooler Boost Trouble Code P0299

The criteria for setting the code is very basic.

A code P0299 for lower- than-normal boost can be one of the most challenging DTCs to resolve. You might think it is a code for a leak, but it could be more than a leak. The criteria for setting the code is very basic. The engine management system is looking at the desired boost pressure and the actual boost pressure, if the actual and desired do not match for the conditions. 

Honda Electronic Throttle Body Service Tips

Using care and following OEM procedures will help you to avoid unnecessary parts replacement and comebacks.

Why Alternators Are Subject To Ripple Voltage

The alternator produces an AC current that must be converted into DC current by way of a rectifier.

Belts and Pulley Alignment

A misalignment of the plane of the belt can occur when a pulley is not parallel to the other pulleys on the belt drive system.

Diagnosing Misfires

What if there are no codes and a misfire is intermittent? This is where it gets complicated.

Other Posts

Auxiliary Water Pump Diagnostics

A car or truck comes into your shop with a complaint of poor heater performance- the issue may be the auxiliary water pump.

Hybrid Vehicle Fluid Maintenance

There are opportunities your shop can’t pass up just because the car or SUV has a hybrid badge on the back.

Ignition Coil Output

To see inductance inside the primary windings, use an amp probe placed around the positive wire for the ignition coil.

Using a Scope

Ignition coil and plug diagnostics.