Another BCM Q? Fuel Related

[CactusWill]

Hate to start a thread for this but can't find information elsewhere.... Does the BCM have ANYTHING to do with fuel delivery? Specifically, when you turn the key forward to on position without starting the car, and the fuel pump comes on for only 3-4 seconds... Then comes back on when you start the car... What sends that signal to the fuel pump?

[cherrington17]

i thought that would be done by the PCM... i am most likely wrong though.

[jackal2000]

the PCM does.

[CactusWill]

PCM stands for?

[01OldsAleroGt]

lets hope C2 doesn't come in here with his VCM corrections lol

Powertrain Control Module

[CactusWill]

So basically, its the engine computer?

[cherrington17]

among other things, yes.

[[ion] C2]

Originally Posted by 01OldsAleroGt

lets hope C2 doesn't come in here with his VCM corrections lol

Powertrain Control Module

hopefully he never sees this thread

[circeansleeper]

^^

[Cliff8928]

This is the only way the BCM has anything do to with fuel control.

Originally Posted by GM

Vehicle Theft Deterrent (VTD) Description and Operation

Passlock™ System

The Passlock™ System is provided in order to prevent vehicle theft if the ignition lock cylinder is forced to rotate or the ignition switch is operated while separated from the ignition lock cylinder case. If starting is attempted without authorization from the Passlock™ System, the powertrain control module (PCM) will disable engine starting. Start disable may be in the form of fuel disable or starter disable, depending on engine application.

The components of the Passlock™ System are as follows:

The ignition lock cylinder and key
The ignition lock cylinder case, including the Passlock™ sensor
The ignition switch
The body control module (BCM)
The security indicator on the instrument cluster
The powertrain control module (PCM)
Ignition Lock Cylinder Case, Including the Passlock™ Sensor

The ignition lock cylinder fits inside the ignition lock cylinder case and operates the ignition switch when turned by a key with the proper mechanical cut. When the ignition key is used to turn the ignition lock cylinder to crank, start, a magnet on the lock cylinder passes close to the Passlock™ sensor within the ignition lock cylinder case. The magnet activates the security hall effect sensor in the Passlock™ sensor which completes a circuit from the security sensor signal circuit through a resistor to the security sensor low reference circuit. The resistance value will vary from vehicle to vehicle.

If a magnet from outside of the ignition lock cylinder case is used to attempt to steal the vehicle, the tamper hall effect sensor will be activated. This completes a circuit from the security sensor signal circuit through a tamper resistor to the security sensor low reference circuit bypassing the security resistor. If the ignition switch is forced to rotate without the correct key, or if the ignition lock cylinder is removed by force, the Passlock™ sensor will be damaged and will not operate.

Ignition Switch

The ignition switch contains the wiring and electrical switching portion of the column mounted ignition assembly. The ignition switch includes wiring pigtails which connect it to the base of column connector, the Passlock™ sensor on the ignition lock cylinder case, and other components. The wiring for the Passlock™ sensor is unaffected by ignition switch position. The electrical switch portion is operated by the key and lock cylinder when they are rotated within the ignition lock cylinder case. The ignition switch operates the crank relay regardless of the status of the Passlock™ System.

Body Control Module (BCM)

The body control module (BCM) contains the logic of the Theft Deterrent System. The BCM provides the battery positive voltage to operate the Passlock™ sensor. The BCM also measures the voltage of the security sensor signal circuit. The voltage measured will indicate whether the Passlock™ sensor has been activated and whether the resistance value from the sensor is a valid value or the tamper value. If voltage measured is in the valid range, the BCM compares this voltage, voltage code, to a previously learned voltage code. If the voltage codes match, the BCM sends a class 2 message containing a password to the powertrain control module (PCM). If the voltage codes do not match, or the voltage is in the tamper range, or there is a circuit fault, the BCM will not send the correct password to the PCM, and the vehicle will not start.

Powertrain Control Module

The powertrain control module (PCM) contains the remainder of the logic of the Theft Deterrent System. If a class 2 message containing a valid password is received from the body control module (BCM), the PCM will continue to allow the fuel injectors to operate. The PCM will allow the fuel injectors to operate until it decides there is no valid password coming from the BCM. If the PCM does not receive a class 2 message, or receives a class 2 message with an incorrect password, the engine will crank and will not run or will start and stall immediately.

Theft System Indicator

The IPC illuminates the theft deterrent indicator as determined by the theft deterrent system. The IPC receives a class 2 message from the BCM requesting illumination.

The vehicle theft deterrent (VTD) system requests the IPC to illuminate the indicator only when the ignition switch is ON.
The content theft deterrent (CTD) system requests the IPC to illuminate the indicator only when the ignition switch is in the OFF or ACC positions or during RAP.
The body control module performs the displays test at the start of each ignition cycle. The indicator illuminates for approximately 3 seconds.
Fuel Lockout Cycle

When it receives a password which is incorrect or a password which indicates tamper and the powertrain control module (PCM) disables the fuel injectors, the fuel injectors remain disabled for 10 minutes even if the ignition switch is turned from the RUN position to the OFF position.

Changing the Passlock™ Components

The following components contain codes or passwords, or must learn codes or passwords for the Passlock™ System to allow the vehicle to start:

The ignition lock cylinder case
The body control module (BCM)
The powertrain control module (PCM)
If any of these parts are replaced, a learn procedure must be performed. Refer to Programming Theft Deterrent System Components . If parts are replaced and a learn procedure is not performed, the engine will crank and will not run or will start and stall immediately.