Crankshaft Position (CKP) - Variation Learn Procedure

STEPS 1-4:
1. Start engine.
2. Using Scan tool, monitor MISFIRE CURRENT and HISTORY CYLs #1-4 to make sure no misfires exist. Correct a misfire condition if one exists.

NOTE: The PCM will not learn the crankshaft if a misfire is present.

3. Using Scan tool or Service Stall System (SSS), perform the CRANKSHAFT POS. VARIATION LEARN procedure.
4. When the SERVICE telltale flashes, accelerate engine (with accelerator pedal) to 3500 RPM. The PCM will take 2 engine revolutions to learn the crankshaft notch variation.

CRANKSHAFT POSITION VARIATION PROCEDURE EXPLAINED
When the procedure is initiated, the Scan tool will send a message to the PCM to reset the CRANK LEARNED adaptive to NO. After this is accomplished, a delay counter in the PCM will remain constant until all of the misfire criteria has been met or MISFIRE ENABLED is set to YES on Scan tool.

IMPORTANT: If vehicle speed is present or if TP angle is greater than 2.3% when CRANK LEARNED adaptive is NO, the delay counter will increment and the ignition will have be cycled Off for 10 seconds to reset the counter. The entire procedure will have to be repeated.

MISFIRE ENABLE CRITERIA
^ Engine run time is greater than 20 seconds (only when CRANK LEARNED is set to NO).
^ Engine speed is between 562 and 5500 RPM.
^ ECT is between -7° and 118°C (20° and 244°F). If ECT is less than -7°C (20°F), the PCM will wait until ECT is greater than 20°C (68°F).
^ Ignition voltage is between 8 and 18 volts
^ Fuel level is greater than 3.8 L (1 gallon)
^ No cam, CKP, ECT, IAC valve, IAT, MAP, TP or VSS DTCs have been set

As soon as MISFIRE ENABLED = YES when CRANKSHAFT LEARNED = NO, no misfires can exist. The PCM will then start to decrement the delay counter down to zero, which will take 2 engine revolutions. Once the delay counter is at zero, a 400 revolution test at idle is performed to determine if the engine idle is stable enough to perform the relearn procedure. At this time the PCM determines if any misfires are present.

IMPORTANT:
^ If one misfire occurs during the 2 + 400 revolution test, the PCM will not learn the crankshaft for that ignition cycle. The ignition will have to be turned Off for 10 seconds and the entire procedure repeated.
^ When monitoring misfires, use Scan tool to monitor MISFIRE CURRENT CYLs. #1-4 and MISFIRE HISTORY CYLs. #1-4. The current misfire counters will update to the history counters every 200 revolutions and the current counters will be reset to zero. The history counters are reset every ignition cycle.

After the PCM has run the 2 + 400 revolution test without any misfires, the SERVICE telltale will flash. The PCM will then wait for the engine RPM to be raised between 3000 and 4000 RPM. The PCM will then take two crankshaft revolutions to learn the crankshaft variation. The procedure is now completed.

NOTE:
^ The relearn process may be difficult for the PCM to perform if ignition and/or fuel control components are worn e.g. spark plugs, wires etc.
^ Loading down the engine by turning accessories On (A/C, headlights, rear defog) may improve idle stability and help to relearn the crankshaft.
^ If a very seldom misfire occurs at idle and the cause cannot be identified causing difficulty with the crankshaft relearn procedure, follow these steps (A/T only).

1. Turn Off the engine for 10 seconds then turn ignition On (do not start).
2. Go into the Scan tool relearn procedure, but do not choose option.
3. Start the engine.
4. Turn On all accessories.
5. Set the park brake to secure vehicle.
6. Initiate the relearn procedure using Scan tool then go immediately to step 7.
7. Place the transaxle in drive. If more than 15 seconds elapsed from when engine was started until the transmission was placed in drive, repeat procedure quicker.
8. Wait for the SERVICE telltale to flash.
9. Place transaxle in neutral.
10. Accelerate engine to 3500 RPM. Crankshaft variation procedure should be complete.