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Tim's Auto Repair
Tim's Auto Repair, mechanic
Category: Chevy
Satisfied Customers: 15472
Experience:  Have owned a repair shop for 25 yrs.
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Do you need to reset the computer after changing the battery

Customer Question

Do you need to reset the computer after changing the battery on a 1999 chevy express 2500? And if so, how do you do it? Thanks, Jack
Submitted: 6 years ago.
Category: Chevy
Expert:  Tim's Auto Repair replied 6 years ago.

hi

most of the time when you change the battery you will need to do a passlock auto relearn and an idle relearn

thanks

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The following is the Auto Learn Procedure:

  1. Insure the ignition key is in the ON position.
  2. Clear all EVO/PASSLOCK(TM) module and VCM/PCM DTCs.
  3. Momentarily rotate the ignition key to the CRANK position (Do NOT start the vehicle), then release it to the RUN position (Do NOT key OFF in the process).
  4. Wait 10 minutes . Observe the SECURITY indicator. Refer to the following list for the appropriate responses:
    • If the PASSLOCK(TM) sensor was replaced the SECURITY indicator will flash for the 10 minutes duration.
    • If the EVO/PASSLOCK(TM) module was replaced, the SECURITY indicator will flash for a few seconds and then remain ON for the remainder of the 10 minutes duration.
    • If the VCM/PCM was replaced with a new programmed VCM/PCM and connected to the vehicle for the first time, the vehicle will start and this procedure may not be necessary.
    • If the replacement VCM/PCM was connected to any vehicle at any other time, even momentarily, the SECURITY indicator will flash for a few seconds and then remain ON for the 10 minutes duration.
  1. The SECURITY indicator will transition from flashing to ON briefly to OFF after 10 minutes if remaining in the ignition ON position.
  2. Turn the ignition switch to the OFF position and wait for 10 seconds .
  3. Repeat steps 3-6 two more times. The new security code is ready to be communicated among the PASSLOCK sensor, EVO/PASSLOCK module and VCM/PCM. The new password XXXXX XXXXX on the next ignition lock cylinder cycle from OFF to CRANK to ON (start attempt).

Idle Air Control (IAC) Reset Procedure
  1. Turn the ignition switch to the ON position for 5 seconds.
  2. Turn the ignition switch to the OFF position for 10 seconds.
  3. Start the engine.
  4. Check for the proper idle operation.

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.
  4. Set the parking brake and block the drive wheels.
  5. Start the engine.
  6. Ensure that the engine coolant temperature is more than 80°C (176°F) .
  7. Shift the transmission into Drive.
  8. Allow the engine to idle for 5 minutes .
  9. Shift the transmission into Park.
  10. Allow the engine to idle for 5 minutes .
  11. 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.
  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 80°C (176°F) .
  8. Allow the engine to idle for 5 minutes .
  9. Turn OFF the engine for 30 seconds .
Tim's Auto Repair and other Chevy Specialists are ready to help you
Customer: replied 6 years ago.
Tim, How do you get the water temp to 176f if the engine won't stay running?
Expert:  Tim's Auto Repair replied 6 years ago.

it should run after you do the passlock relearn

thanks