It's happened twice this week. I get in my car, put the key ignition, attempt to start her up and nothing. I get this code: PCM-1631. Should I take it to the dealer?

 

Try cleaning your key :)

 

Been there, done that :(. It keeps coming back :(

 

If checking connections at the BCM and battery don't turn up anything I'd probably take it in since it seems persistant. :smash:

 

Check this out you may need to go and relearn the pass word for the BCM.--------------------------------------------------------------------------------

DTC P1631 Theft Deterrent Start Enable Signal Not Correct
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 PCM.

Conditions for Setting the DTC
The PCM detects a wrong password from 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 DTC
A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
Use a scan tool in order to clear the 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.

DTC P1631 Theft Deterrent System-Password incorrect Step
Action
Values
Yes
No

1
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?
--
Go to Step 2
Go to Powertrain On Board Diagnostic (OBD) System Check

2

Important
Inspect for any BCM DTCs being set (except if you were sent here from PCM Replacement) before proceeding with this table. If a BCM DTC is set, refer to the appropriate BCM DTC.


Is a Tech 2® available?
--
Go to Step 4
Go to Step 3

3

Important
This step is for United States and Canada vehicles only.
Maintain the battery voltage while the PCM is in the Auto Learn Procedure. Follow this procedure exactly as indicated or you will have to repeat the procedure from the beginning.
Performing the following procedure causes a DTC P1630 to set when you complete the procedure. This is the intended functionality. When P1630 sets, turn OFF the ignition for 30 seconds, then turn ON the ignition and P1630 clears. If the DTC P1630 does not clear, refer to the DTC P1630 Theft Deterrent Learn Mode Active table.

Turn ON the ignition leaving the engine OFF for 11 minutes.
Turn OFF the ignition for 30 seconds.
Turn ON the ignition leaving the engine OFF for 11 minutes.
Turn OFF the ignition for 30 seconds.
Turn ON the ignition leaving the engine OFF for 11 minutes or until DTC P1630 sets.
Turn OFF the ignition for 30 seconds.
Turn ON the ignition leaving the engine OFF and wait 30 seconds.
Attempt to start the engine.
Does the engine start and operate normally?
--
Go to Step 5
Go to Step 6

4

Important
Performing the following procedure causes a DTC P1630 to set when you complete the procedure. This is the intended functionality. When P1630 sets, turn OFF the ignition for 30 seconds, then turn the ignition ON and P1630 clears. If the DTC P1630 does not clear, refer to the DTC P1630 Theft Deterrent Learn Mode Active table.


Enter the Service Programming System (SPS) using a Tech 2.
Enter the vehicle information.
Choose the Request Info soft key on the scan tool.
Select Done.
Follow the instructions on the Vehicle Set-up screen.
Disconnect the scan tool from the vehicle.
Connect the scan tool to the Techline terminal.
At the Techline terminal select Service Programming System (SPS) and select terminal to Tech 2 programming method.
Select Done.
Follow the instructions on the remaining screens.
Select the Vehicle Theft Re-learn option.
Select Program at the summary screen. The terminal will download information to the Tech 2.
Return the scan tool to the vehicle.
Connect the scan tool to Diagnostic Link Connector (DLC).
Select Service Programming from the Tech 2 main menu.
Answer the prompts regarding the model year and vehicle type.
Press the Theft Re-learn soft key on the Tech 2.
Follow the instructions on the remaining screens.
The PCM and the BCM will be prepared for re-learn.
A security timer will be on for approximately 11 minutes or until DTC P1630 sets. It is important that during the 11 minute-wait, the user keeps the Scan Tool connected to the vehicle.
When the PCM and the BCM are prepared to re-learn, turn OFF the ignition for 30 seconds and then start the engine.
Does the engine start and operate normally?
--
Go to Step 5
Go to Step 6

5

Important
Monitor all DTC status parameters and note any additional DTCs before Clearing DTCs.


Clear the PCM DTCs.
Turn OFF the ignition for 30 seconds.
Attempt to start the engine.
Does the engine start and operate normally?
--
System OK
Go to Step 6

6
Are DTCs P1626, P1630 or P1631 set?
--
Go to the applicable DTC table
Go to Step 2



David Fulcher

 

After that reply by DavidF, take it to the dealer.

 

Not to challenge David-F's wisdom, but I'd still vote for something simple like cleaning the battery terminals before a trip to the dealer. The question is why is the serial data communication is failing. I'm an Occam's Razor kind of guy and go for the simple causes first :)