[MxMelkor]

Hello all, I have an 03 with the 3.8 that I’ve been trying to fix for a month now as I’ve had what seems to be cascading failures.

So far I’ve replaced the radiator, cooling fans, fuel pump, fuel filter, removed and cleaned the fuel rails, replaced the fuel pressure regulator, vacuum harness, alternator, battery, plugs and wires, and ignition cylinder and it’s pigtail. The last one was done when my security light came on and the car wouldn’t start. After replacing it the car started multiple times and ran for about an hour and a half, just to be back to no start and security light the next day.

Currently the security light is on and the starter cranks but usually won’t start, and if it does start it sputters and dies within a couple seconds. I’m suspecting the Bcm since I’ve done relearn, radio reset and pulled and replaced all Bcm fuses.

Is there any way I can test the Bcm to make sure it’s the problem? And has anyone had any luck with preprogrammed plug and play bcms?

This is currently my only vehicle and I’m desperate to get it running so I can stop begging friends for rides whenever I need to go somewhere

 

[MxMelkor]

I forgot to add, there are no codes currently and the only ones I’ve seen have been for the MAF when it’s unplugged and an intermittent misfire on cylinder 3. I’ve also cleaned the throttle body and replaced the IAC as well.

 

[hatzie]

You're having problems with the Passlock 2 security system.
It can be bypassed.

 

[MxMelkor]

You're having problems with the Passlock 2 security system.
It can be bypassed.

I don’t think a bypass is going to help in this case, I’ve already replaced the lock cylinder and the new one is reading a voltage drop in the correct range. If the BCM is bad a bypass isn’t going to fix it anyway so far as I understand it unless there’s another part of the passlock system I’m not aware of that could be causing the problem.

As I understand it the sensor on the lock cylinder goes directly to the BCM and that’s the entirety of the components in that system, right?

 

[MrSoftee]

The ignition switch is the one thing you haven't mentioned that's a common cause of passlock issues and other electrical problems. Replace the ignition switch and spend the extra $$$ on an ACDelco one. The lock cylinder is attached to a passlock hall sensor and that part can fail as well. When you replaced the lock cylinder, did you replace the passlock sensor with it?

The BCM is also another possible fix but I don't have much experience there.

 

[MxMelkor]

The ignition switch is the one thing you haven't mentioned that's a common cause of passlock issues and other electrical problems. Replace the ignition switch and spend the extra $$$ on an ACDelco one. The lock cylinder is attached to a passlock hall sensor and that part can fail as well. When you replaced the lock cylinder, did you replace the passlock sensor with it?

The BCM is also another possible fix but I don't have much experience there.

Yes, the lock cylinder came with a new hall sensor. The old one was only reading a very small drop in voltage and the new one is in the correct range.

I haven’t replaced the ignition switch since the passlock sensor is on the lock cylinder, can the switch cause passlock issues as well?

 

[hatzie]

I really dislike changing expensive parts like the BCM without doing some investigation. Investigation is a darnsight cheaper than replacing parts and discovering the problem was elsewhere afterward.

Have you done a BCM ignition reference voltage relearn?

Relearn procedure:
1) Turn the ignition switch to the 'Run' position. Wait several seconds, then turn the switch to 'Start' for several seconds, then release the key back to 'Run'. The security light should be on/blinking.
2) Wait approximately 10 minutes for the light to turn off. If the light does not turn off after more than about 12 minutes, something other than the Passlock system requires maintenance.
3) Turn the ignition to 'Off' and wait 5 seconds.
4) Repeat steps 1-3 two more times for a total of 3 cycles/30 minutes.
5) The BCM will now read and store the new system reference value on the next ignition cycle from 'Off' to 'Start'.
6) Start the vehicle and clear any codes in the system.

Have you gone over the hall sensor wires to verify they aren't damaged and the pins/terminals aren't corroded or loose?

 

[MxMelkor]

I really dislike changing expensive parts like the BCM without doing some investigation. Investigation is a darnsight cheaper than replacing parts and discovering the problem was elsewhere afterward.

Have you done a BCM ignition reference voltage relearn?

Relearn procedure:
1) Turn the ignition switch to the 'Run' position. Wait several seconds, then turn the switch to 'Start' for several seconds, then release the key back to 'Run'. The security light should be on/blinking.
2) Wait approximately 10 minutes for the light to turn off. If the light does not turn off after more than about 12 minutes, something other than the Passlock system requires maintenance.
3) Turn the ignition to 'Off' and wait 5 seconds.
4) Repeat steps 1-3 two more times for a total of 3 cycles/30 minutes.
5) The BCM will now read and store the new system reference value on the next ignition cycle from 'Off' to 'Start'.
6) Start the vehicle and clear any codes in the system.

Have you gone over the hall sensor wires to verify they aren't damaged and the pins/terminals aren't corroded or loose?

I’ve attempted the relearn multiple times and the security light never turns off and it has never worked. The wires to the hall sensor were replaced as was the connector. I’ve also pulled the connectors at the BCM and they appear clean and corrosion free. The BCM is original based on the part number which had an advisory issued on it by GM at one point.