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Gary
Gary, Chevy Technician
Category: Chevy
Satisfied Customers: 17033
Experience:  15 years GM master tech
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Got a trouble code of p1631 Main Relay (power hold) on my 99

Customer Question

got a trouble code of p1631 Main Relay (power hold) on my 99 corvette. car runs fine, but I have had two instances where it wouldn't start, and eventually did for no apparent reason. There were no codes then, the dealer checked it out and found nothing, but this morning while driving the check engine light came on and that was one of the codes. The other is p0430 cat efficiency below threshold (bank 2). I'm not too concerned about that one at the moment.
JA: Does the light stay on, or does it blink?
Customer: stays on. I just reset the codes, but haven't driven it yet to see if they come back
JA: Are you fixing your Corvette yourself? What have you tried so far?
Customer: all I've done is scan and reset so far.
JA: Anything else you want the mechanic to know before I connect you?
Customer: I replaced the ignition relay a week ago, cuz the second time it wouldn't start I pulled a fan relay, stuffed it in the ign relay slot and it started right up.
Submitted: 4 months ago.
Category: Chevy
Expert:  Gary replied 4 months ago.

Welcome! My name is ***** ***** I will do my best to assist you with this problem.Ask me about added features such as phone contact anytime if you wish !

Expert:  Gary replied 4 months ago.

a P1631 is a theft password ***** code

it sets when the BCM does not send the correct password ***** the PCM

this is usually set with a bad connection at the BCM or a bad BCM

Circuit Description This diagnostic tests for mismatched passwords between the BCM and PCM. Whenever replacing the BCM or PCM, follow the theft learn procedure in order for the system to learn the new password.Conditions for Running the DTC Mismatched passwords between the BCM and the PCMConditions for Setting the DTC

  • The PCM detects a wrong password ***** the BCM.
  • The fuel disable lockout is set.
  • The system has received an incorrect fuel continue password.
  • An invalid ignition key or malfunctioning ignition switch.
  • The BCM was replaced.
  • Action Taken When the DTC Sets
  • The engine starts and then the engine stalls immediately.
  • The PCM stores the DTC information into the memory when the diagnostic runs and fails.
  • The Malfunction Indicator Lamp (MIL) will not illuminate.
  • The PCM records the operating conditions at the time during which the diagnostic fails. The PCM stores this information in the Failure Records.
  • Conditions for Clearing the MIL/DTC
  • A History DTC will clear after forty consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
  • A last test failed (Current DTC) will clear when the diagnostic runs and does not fail.
  • Use a scan tool in order to clear the MIL/DTC.
  • Test Description
    The numbers below refer to the step numbers on the diagnostic table.
  • The 11 minute and 30 second time criteria are a minimum required amount of time. The time limit can exceed this limit without interfering with the Auto Learn Procedure. Use a scan tool (VTD Auto Learn Timer equals Inactive) in order to determine when the 11 minutes has expired.
  • If DTC P1631 is set, this indicates that you did not follow the procedure correctly. Perform the Re-learn procedure again.
  • please dont forget to rate me here at Justanswer you can always get me back for FREE for any follow up any time with this question even after you rate me here at Justanswer if you have any questions please ask as i do not get credit for my work until you rate me here at Justanswer
    Expert:  Gary replied 4 months ago.

    please dont forget to rate me here at Justanswer

    you can always get me back for FREE for any follow up any time with this question even after you rate me here at Justanswer

    if you have any questions please ask as i do not get credit for my work until you rate me here at Justanswer

    Expert:  Gary replied 4 months ago.

    how are you making out ?

    please dont forget to rate me here at Justanswer

    you can always get me back for FREE for any follow up any time with this question even after you rate me here at Justanswer

    if you have any questions please ask as i do not get credit for my work until you rate me here at Justanswer