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2002 gmc envoy_sle
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I'm considering buying a junked PCM and getting a flash from PCMforLess or one of the custom vendors. The only thing that's getting me confused is regarding the CASE relearn that's required. Dealing with the local dealerships is a major pain in the a$$, and i've already gotten quotes for around $100 to get the relearn done.

With that said, I stumbled across this bulletin which covers the process for a "manual" relearn. I was under the impression that the only way to get the relearn initiated was via a TECH II tool, but it seems that it can also be initiated with specific driving.

Can anyone out there advise if this is applicable to the Trailvoy?

CRANKSHAFT VARIATION RELEARN (CASE Learn)

”CASE” means: crankshaft angle sensor error. A crankshaft variation relearn must be performed if:

A diagnostic trouble code of P1336 is present. (A P0300 code means cylinder misfires detected)
The computer has been replaced or re-programmed.
The crankshaft position sensor has been replaced.
The engine, harmonic balancer, clutch, or flywheel have been: disassembled, removed, or replaced.
The crankshaft position variation learning feature enables the computer to compensate for part manufacturing tolerances. This allows the computer to accurately detect an engine misfire throughout the engine RPM range. The learning process is stored in the computer’s memory and does not have to be repeated unless one or more of the above conditions are present.


To perform the relearn, proceed as follows:

Connect a scan tool to make sure there are no trouble codes stored in the computer’s memory. If there is any power train trouble code other than P1336 (Crankshaft Position Variation not learned), the computer will disable the relearn function until the problem that caused the code has been eliminated. Also, make sure that the engine coolant (check it when the engine is cold) and oil levels are at an acceptable level.

1. Set the parking brake and block the drive wheels. Make sure that the hood is closed.
2. Start the engine and make sure that the engine coolant temperature is at least 158 degrees F. (70 degrees C.)
3. Turn the engine off for at least 10 seconds.
4. Select the crankshaft position variation learn procedure (CASE Learn)on your scan tool.
5. Make sure that the transmission is in Park. Start the engine.
6. Apply the brakes and hold the pedal firmly.
7. Follow the scan tool instructions.

Remember: That you are going to increase the engine speed to approximately 3000 RPM, 4000 RPM, or 5150 RPM. That’s the variation learn fuel cutoff RPM (depending upon the engine), and that it’s important to release the throttle when the engine RPM starts to decrease as a result of the fuel cutoff going into effect. Failure to do such will result in over revving of the engine, causing possible engine damage.

8. Once the engine has returned to idle, check the status of Diagnostic trouble code P1336. If the scan tool indicates that the CASE has been learned, the relearn procedure is now complete. If CASE has not been learned, check for the presence of other power train codes. If any exist, correct the problem, then repeat this procedure.

NOTE: If the Crankshaft Variation Relearn is not accessible through your scan tool (some truck applications 1998 & later), perform the relearn in the following manner:

1. Turn off all of the accessories. With the Air temperature sensor and Coolant temperature within 5 degrees (Centigrade) of each other, start the engine and let it idle in Park or Neutral for two minutes.
2. Accelerate the vehicle to 55 mph at part throttle. Cruise at 55 mph for 8- 10 minutes until the engine reaches operating temperature.
3. Cruise at 55 mph for another 5-6 minutes.
4. Decelerate to 45 mph without using the brakes, and maintain 45 mph for 1 minute.
5. Perform 4 deceleration cycles, without using the brakes, of 25 seconds each where no specific speed is necessary. Returning to 45 mph for 15 seconds in between deceleration cycles.
6. Accelerate to 55 mph and cruise for 2 minutes.
7. Stop the vehicle and idle for 2 minutes with the brake applied and the transmission in Drive (automatic trans.) or Neutral (manual trans.) with the clutch depressed.
 

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2004 gmc
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26,181 Posts
I don't know about the manual process, but don't give up on independent GM-qualified mechanics. Most of them have capable scan tools, and one of them local to me charges a lot less than $100 for the service. You should be able to find somebody for $40-50, unless they ALL have kids they're sending to dental school at the same time.
 

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Registered
2005 chevy trailblazer_lt
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363 Posts
I am in the same boat as you Mike. I posted on another thread about a gauge that is available that plugs into the OBD2 port and does the CASE relearn. Maybe a moderator here or someone else can get one and rent it out to us.
 

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2003 gmc envoy_slt
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361 Posts
I'm considering buying a junked PCM and getting a flash from PCMforLess or one of the custom vendors. The only thing that's getting me confused is regarding the CASE relearn that's required. Dealing with the local dealerships is a major pain in the a$$, and i've already gotten quotes for around $100 to get the relearn done.

With that said, I stumbled across this bulletin which covers the process for a "manual" relearn. I was under the impression that the only way to get the relearn initiated was via a TECH II tool, but it seems that it can also be initiated with specific driving.

Can anyone out there advise if this is applicable to the Trailvoy?

CRANKSHAFT VARIATION RELEARN (CASE Learn

”CASE” means: crankshaft angle sensor error. A crankshaft variation relearn must be performed if:

A diagnostic trouble code of P1336 is present. (A P0300 code means cylinder misfires detected)
The computer has been replaced or re-programmed.
The crankshaft position sensor has been replaced.
The engine, harmonic balancer, clutch, or flywheel have been: disassembled, removed, or replaced.
The crankshaft position variation learning feature enables the computer to compensate for part manufacturing tolerances. This allows the computer to accurately detect an engine misfire throughout the engine RPM range. The learning process is stored in the computer’s memory and does not have to be repeated unless one or more of the above conditions are present.


To perform the relearn, proceed as follows:

Connect a scan tool to make sure there are no trouble codes stored in the computer’s memory. If there is any power train trouble code other than P1336 (Crankshaft Position Variation not learned), the computer will disable the relearn function until the problem that caused the code has been eliminated. Also, make sure that the engine coolant (check it when the engine is cold) and oil levels are at an acceptable level.

1. Set the parking brake and block the drive wheels. Make sure that the hood is closed.
2. Start the engine and make sure that the engine coolant temperature is at least 158 degrees F. (70 degrees C.)
3. Turn the engine off for at least 10 seconds.
4. Select the crankshaft position variation learn procedure (CASE Learn)on your scan tool.
5. Make sure that the transmission is in Park. Start the engine.
6. Apply the brakes and hold the pedal firmly.
7. Follow the scan tool instructions.

Remember: That you are going to increase the engine speed to approximately 3000 RPM, 4000 RPM, or 5150 RPM. That’s the variation learn fuel cutoff RPM (depending upon the engine), and that it’s important to release the throttle when the engine RPM starts to decrease as a result of the fuel cutoff going into effect. Failure to do such will result in over revving of the engine, causing possible engine damage.

8. Once the engine has returned to idle, check the status of Diagnostic trouble code P1336. If the scan tool indicates that the CASE has been learned, the relearn procedure is now complete. If CASE has not been learned, check for the presence of other power train codes. If any exist, correct the problem, then repeat this procedure.

NOTE: If the Crankshaft Variation Relearn is not accessible through your scan tool (some truck applications 1998 & later), perform the relearn in the following manner:

1. Turn off all of the accessories. With the Air temperature sensor and Coolant temperature within 5 degrees (Centigrade) of each other, start the engine and let it idle in Park or Neutral for two minutes.
2. Accelerate the vehicle to 55 mph at part throttle. Cruise at 55 mph for 8- 10 minutes until the engine reaches operating temperature.
3. Cruise at 55 mph for another 5-6 minutes.
4. Decelerate to 45 mph without using the brakes, and maintain 45 mph for 1 minute.
5. Perform 4 deceleration cycles, without using the brakes, of 25 seconds each where no specific speed is necessary. Returning to 45 mph for 15 seconds in between deceleration cycles.
6. Accelerate to 55 mph and cruise for 2 minutes.
7. Stop the vehicle and idle for 2 minutes with the brake applied and the transmission in Drive (automatic trans.) or Neutral (manual trans.) with the clutch depressed.
Back in '06 when I got my Wait4me PCM, Jesse told that the crankshaft angle should be close but he sent this procedure along with a chart of accelerations, maintaining, decelerations and stop procedure for a manual relearn. He also said that besides dealers a lot of transmission shops had the tool to do a case relearn. I did the manual and never tried the dealer or transmission shops.
 

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2004 chevy trailblazer_ltz
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8 Posts
I replaced the CPS on my wife's Trailblazer, then cleared out the stored OBD codes and drove it for a while. I never had to perform the CASE relearn procedure like everyone else has.

The other thing you can do is just disconnect the negative terminal, step on the brake or ground the negative to positive to drain current and then reconnect the battery. Then turn off all accessories and let the engine idle for 10 minutes with no load for it to relearn IDLE and then go drive around a few miles as you would normally.

I don't see the need for a drawn out CASE relearn procedure which is basically doing the same thing.
 

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2005 chevy trailblazer_lt
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363 Posts
Has anyone here had a code thrown for the CASE relearn and had it clear itself by doing the manual relearn procedure described above?
 

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I replaced the CPS on my wife's Trailblazer, then cleared out the stored OBD codes and drove it for a while. I never had to perform the CASE relearn procedure like everyone else has.

The other thing you can do is just disconnect the negative terminal, step on the brake or ground the negative to positive to drain current and then reconnect the battery. Then turn off all accessories and let the engine idle for 10 minutes with no load for it to relearn IDLE and then go drive around a few miles as you would normally.

I don't see the need for a drawn out CASE relearn procedure which is basically doing the same thing.
This worked thank you soo much! I knew it was a sign when I saw the post was from my Bday but 11 years ago HAHA man what a headache but the truck is running soo smooth I cant even feel it now! DRAINING the Bat is the only answer as disconnecting is not enough!! Thanks again for this!
 
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