Well, I was driving along with a 1/4 tank of gas. My needle falls to Empty and I get LOW FUEL and the Check Gauges light illuminates. Then I get BCM NO COMM on my DIC. I have had the fuel sending unit replaced and all that jazz to remedy the erratic fuel gauge problem. I have also been experiencing times of not being able to start my car at all due to the theft deterrent system. I get the code P-1631 for that. I have cleaned the key and ignition with alcohol several times and it happens every now and again. It usually takes 10 minutes of cycling the ignition to get the car to start. Now I have the erratic fuel gauge occuring and the first appearance of BCM NO COMM on the DIC.

What am I to do? Thank you very much.

 

Hmmmm maybe this could help :

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.

Sounds like your problemThe 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 NO for you so 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


© Copyright General Motors Corporation. All Rights Reserved.


--------------------------------------------------------------------------------
Document ID # 554915

DTC P1630 Theft Deterrent Learn Mode Active
Circuit Description
This diagnostic tests for the Enable Password Learning Flag indicating the PCM is in learn password mode. This mode allows the PCM to learn the password from the body control module (BCM) at assembly or when serviced. The password needs to be learned whenever the PCM or the BCM is replaced or if a replacement ignition key that has a different resistance is used.

Conditions for Running the DTC
The PCM is ready to learn a new password from the BCM.

Conditions for Setting the DTC
The BCM is not sending a valid password or not sending a password at all.

Action Taken When the DTC Sets
The engine starts and stalls when the BCM detects a theft mode.
The engine starts and stalls when the PCM losses communication with the BCM.
The engine operates normally, but an internal BCM failure has occurred.
The PCM stores the DTC information into 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.
Diagnostic Aids
A DTC 1630 is a code used at the assembly plant, dealership, or repair facility which indicates that the system has enabled the learn mode. This means that the PCM is now ready to learn a new password from the BCM. This DTC sets because the BCM never sent a valid password to the PCM while in the learn mode. When this occurs, the vehicle is vulnerable to vehicle theft.
For an intermittent condition, refer to Symptoms .
DTC P1630 Theft Deterrent System-PCM in Learn Mode Step
Action
Values
Yes
No

1
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?
--
Go to Diagnostic System Check - Body Control System in Body Control System
Go to Powertrain On Board Diagnostic (OBD) System Check

:cheers:





[Modified by intel55, 6:33 PM 3/10/2002]

 

good work intel55

 

Woah. Where do I begin, lol. Should I just attempt the relearn first? If that doesn't work (set the P1630 code) I don't have access to a Tech II tool, only autotap. Should I just let the dealer handle it? Thanks.

 

try the step #3 I have in bold :D Hopefully that will do something for your 1631 code

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?

 

if it then starts normally after the relearn, then go to step 5 :

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?
:cheers:

 

Levi, you need to fix the cause, not the symptom. Fix your voltage problem.

:smash: :smash: :smash:

 

ToplessTexan, go see my post on the other forum, I posted about the voltage :)

 

I understand you have a charged battery. You're not consistently seeing that voltage at the BCM though...

 

How do I check the voltage at the BCM and what should it read? If it's below par, what do I do then get a new BCM?

 

Actually I had the same problem with my '02 a month after I got it...
Called the dealer they picked it up checked it out and they did in this order:
- Replace the key
- Replace the Cylinder Ignition
**it was better but every once in a while go back to having the same problem
-Replaced BCM - bad wiring
Worked good from there....

I tried all the clearing codes and cleaning the key... It started at a vette show around by me... and I even had a tuner give me a hand... He got it started but the problem was still there until the dealer replace the BCM

hope this helps
Mike :cheers:

 

Thanks, Blubyu20002C5. I'll have my dealer replace the BCM and the above items. Anyone know what caused this?

 

Dealer is replacing my BCM :yesnod: I hope this cures my ailments

 

tks

 

Just realized this thread is 12years old