Computer Relearn - Disconnect Battery or Pull Fuses???

[99 MagRedVette]

I have heard of 2 ways to do a computer relearn - either disconnect the batery -or- pull a couple of fuses (16 & 23 I think). Is this doing the same thing or are these 2 different relearn processes? What's the right way to do this after a mod?

[Hool97]

The easiest way is to disconnect the battery for relearn of most variable functions, IMHO.

[Bink]

I have heard of 2 ways to do a computer relearn - either disconnect the batery -or- pull a couple of fuses (16 & 23 I think). Is this doing the same thing or are these 2 different relearn processes? What's the right way to do this after a mod?

I pull the fuses. It's a lot faster and easier than the battery ( 16 and 23 under the hood- both 10 A, red ) Wait about 5 minutes. One or two minutes doesn't seem to be long enough. FWIW.

[C5XTASY]

I have heard of 2 ways to do a computer relearn - either disconnect the batery -or- pull a couple of fuses (16 & 23 I think). Is this doing the same thing or are these 2 different relearn processes? What's the right way to do this after a mod?

The car will re-learn simply by driving it between 50-100 miles. Or, the actual way to do it more quickly, is the following procedure:

1) Insert key into ignition and turn to the “ON” position, but, DO NOT START THE ENGINE.
2) Open the engine compartment fuse box cover and remove the two 10 amp fuses from position numbers 16 & 23.
a) According to the manual there are two fuse boxes. Use the engine compartment fuse block for this procedure not the instrument panel fuse block.
b) Engine Compartment Fuse Block (correct one): 16 is Powertrain Control Module A and 23 is Powertrain Control Module B.
c) Instrument panel fuse block (wrong one): 16 is Air Bag, 22 is Body Control Module-Ignition and 23 is Body Control Module-Ignition 2.
NOTE: Your DIC will now display “check” messages for ABS, etc… Do not worry as this is normal.
3) Turn the ignition key to the “OFF” position.
4) Return to the engine compartment fuse box and re-insert both 10 amp fuses for positions 16 & 23.

5a) Idle relearn for an M6:
1) Start the engine and allow the coolant temp to reach a minimum of 176 degrees F. Allow the engine to run at this minimum temperature for at least 5 minutes.
2) After the 176 degree, 5 minute minimum run, shut down the engine for a minimum of 30 seconds.
3) Restart the engine and check for DIC error codes (there should be none).
5b) Idle relearn for an A4: (different)
1) Start the engine and allow the coolant temp to reach a minimum of 176 degrees F. Allow the engine to run at this minimum temperature for at least 5 minutes.
2) Allow the car to idle in DRIVE, with air ON and then OFF, for 5 minutes each, and then in NEUTRAL, with air ON and then OFF, for 5 minutes each.
3) Turn the car off for at least 30 seconds.
4) Restart the engine and check for DIC error codes (there should be none).
6) Drive car for a minimum of 30 miles at varying rpm settings and speeds. PCM will now re-learn and adjust for the new air flow and temperature at the intake.
a) If error codes persist, repeat steps 1-7. Make sure fuses are properly inserted before repeating steps.
b) Do not deviate from the sequence outlined above. If you do, restart the sequence from scratch.
c) Steps 1-4 are also necessary if you ever disconnect your battery or lose power for any reason.


[Modified by C5XTASY, 9:06 AM 4/10/2004]

[rwj383]

I pull the fuses. It's a lot faster and easier than the battery ( 16 and 23 under the hood- both 10 A, red ) Wait about 5 minutes. One or two minutes doesn't seem to be long enough. FWIW.

What Bink said. The other reason to pull fuses rather than battery is that sometimes when disconnecting the battery a surge can develop as the battery lug arcs/sparks during disconnection. This has a slight chance of spiking the PCM, causing damage. It is always recommended to pull PCM fuses before disconnecting/reconnecting battery.

[Rogerc5]

Thanks to all that replied to my query. Especially to C5XTASY for the info and the time to type it out. :flag And yes it "topic" or I meant "idle relearn".
Again Happy Easter,
Roger

[Hool97]

I like the battery diconnect because for me its actually easier. I have a quick disconnect + capacitors that prevent surges. I have tried the drive a few miles ie 2000mi without the computer learning an idle curve. A quick disconnect and per manual relearn procedure and in 20min. on a A4 it was dead on at 610 rpm smooth with a non stock cam. But , I agree which ever way is easier and safer for your set-up.

[VetteMan4Life]

Why would you want to do this?

[99 vett babycar]

I assume this re-learn procedure is for stock tuned as opposed to custom tuned/ modified cars. Is that correct??

[Jim Shearer]

The Idle Learn procedure in my Corvette Service Manual is different than yours. This is a direct quote.

Idle Learn Procedure
Anytime the Powertrain Control Module (PCM) or the battery is disconnected, the PCM loses power, or the PCM is reprogrammed, the PCMs learned idle position is lost. The engine idle is unstable when the learned idle position is lost.

Perform the following procedure in order to return the learned idle to the correct position:
Automatic Transmission
1. Turn OFF the ignition.
2. Restore the PCM battery feed.
3. Turn OFF the A/C controls, radio, and any other accessories
4. Set the parking brake and block the drive wheels.
5. Start the engine.
6. Ensure that the engine coolant temperature is more than 176°F (80°C).
7. Shift the transmission into Drive.
8. Allow the engine to idle for 5 minutes.
9. Turn on the AC controls (Omit for 2000-01 model)
10. Allow the engine to idle for 5 minutes (Omit for 2000-01 model)
11. Shift the transmission into Park.
12. Allow the engine to idle for 5 minutes (Omit for 2000-01 model)
13. Turn off the AC controls (Omit for 2000-01 model)
14. Allow the engine to idle for 5 minutes.
15. Turn OFF the engine for 30 seconds.

Manual Transmission
1. Turn OFF the ignition.
2. Restore the PCM battery feed.
3. Turn OFF the A/C controls, radio, and any other accessories
4. Set the parking brake and block the drive wheels.
5. Place the transmission in Neutral.
6. Start the engine.
7. Ensure that the engine coolant temperature is more than 176°F (80°C).
8. Allow the engine to idle for 5 minutes.
9. Turn OFF the engine for 30 seconds.