02 Envoy, update PCM with 2005+

[98tsiawd]

Hey guys,
I will be changing my clutch fan in the near future, and I've come across some threads saying to update the PCM with the 2005+, is this a necessity? I also just ordered the loaner option of PCMforless so this will be coming soon, and I'm not sure if I should update the PCM now or just leave it, if it’s not necessary. If I update the PCM now will I benefit from it being I haven’t changed the clutch fan or would it be a bad idea to update before I change out the clutch fan?
sorry for all the questions, I'm trying to figure out the order of what needs to be done first, being that I have the clutch fan to replace, PCMforless tune coming and possible an update from the dealer, this truck being my wife's daily driver I don’t want to tie it up for any longer then I have to.
I appreciate the help.

 

[The_Roadie]

The risk is that if you get a tune from PCMforless and THEN let the dealer touch it, that they will erase the tune and then you're into another loop with PCMforless.

I'm pretty sure if you send yours in for a tune, that they AUTOMATICALLY update the rest of the software to the most current dealer standards. Check with them to be sure, and in case I'm misremembering.

Running the most current software with an old fan clutch will do no harm, and will even get you the benefit of better AC cooling on hot days right after start-up, which is half the benefit of the update anyway.

 

[AtlWrk]

Copied from the OS:

"I've sent my stock PCM to PCMForLess to get tuned. Does anyone know if they flash it with the latest GM calibration or do they just do that with new PCMs shipped out to customers? I'm concerned because I installed a new fan clutch and need the latest and greatest calibration."


"Kelly_PCMforless07-03-2007, 10:41 AM
No.

If I reflash it with the latest cal, then you will have to get a CASE relearn. For send-ins, we just tune it unless directed otherwise (by ordersheet, email, or phone call)."


So you can go to the dealer for the latest calibration then get the tune.
--or--
You can get the tune and the latest calibration then go to a dealer for the CASE relearn.

Chicken or egg?

 

[marshall@pcm]

Seems like I had this exact conversation with someone on the phone yesterday. If you request the most recent updates we will do it for you.

Do NOT let the dealer update it after we tune it, or you'll need to send it back to us to be reprogrammed. :

 

[The_Roadie]

A CASE relearn can be done by many, if not most, independent mechanics with a decent scan tool. Some members have reported getting away for as little as $25. I don't think I've heard of a dealer doing the PCM update for anything less than $90. So the best of both worlds is probably to get the update from Marshall, and then a CASE relearn from a local independent mechanic when you get it back. It's driveable for a short time to go get the CASE relearn. Call around first to your local trusted independents.

 

[98tsiawd]

When you guys talk about the case relearn, it this regarding the transfer case? I mentioned it to a couple of mechanics who have the snap on scan tool but they havnt heard the term case relearn before.
Thanks for the help

 

[The_Roadie]

Crankshaft Angle SEnsor. Its output needs to be calibrated because every sensor is slightly different, an unavoidable design issue. When you change the sensor, it needs to be recalibrated. When you flash an update into a PCM, the sensor calibration data is blown away and it needs to be recalibrated. Just installing a tune or pulling the battery on the PCM doesn't clear this precise location in memory, however, which is why you don't hear about more people needing a CASE relearn.