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

Spark Plug Replacement

Here are some tips to follow when replacing a spark plug.

Every time a spark plug fires, the spark burns a few molecules of metal off the plug’s electrodes. Over time, this eats away the electrodes and rounds off their sharp edges. The erosion gradually increases the gap between the electrodes, which, in turn, increases the firing voltage required to generate a spark. Eventually, the point is reached where the ignition system fails to produce enough voltage and the plug misfires.

What Happened To Turbo Lag In Today’s Engines?

Yesterday’s turbo lag was eliminated thanks to years of development and a bit of clever engineering.

Understanding Engine Timing – Chains, Gears and Belts

Perfect timing is critical in the performance world, and now, it’s required by your regular customers too.

Cartridge Oil Filters

Mistakes made can result in costly comebacks.

Aging Plastic Intake Components May Cause Leaks

BMW valve covers and intake manifolds made of plastic are susceptible to warpage and gasket failure.

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.

PCV System DTC

PCV systems are far more complex now, but they are also much better at controlling crankcase pressure.

Fuel Trims

To gain a better perspective on fuel trims, think about how “analog” vehicles dealt with changing fuel and air mixtures.

It Worked Before I Brought It In

These words can drive any repair facility crazy.