The Body Control Module (BCM) on Nissan and Infiniti vehicles controls various electrical components, including the vehicle immobilizer system and the power door lock system
SYSTEM FUNCTION
The power lock system relies on the Intelligent Key to transmit button operation to the remote keyless entry receiver to function. The remote keyless entry receiver receives each button operation signal and electronic key ID signal from the Intelligent Key and then transmits the signal to the BCM. The Intelligent Key has 2 IDs [Intelligent Key ID and NVIS (NATS) ID]. The BCM performs ID verification between the BCM and Intelligent Key when the Intelligent Key is carried into the detection area of the outside key antenna so it can perform the door lock/unlock operation. When the BCM detects that a door request switch is pressed, it activates the outside key antenna corresponding to the pressed door request switch and transmits the request signal to the Intelligent Key. If the Intelligent Key is within the outside key antenna detection area, it receives the request signal and transmits the key ID signal to the BCM via the remote keyless entry receiver. If these conditions are satisfied, door lock/unlock operation is performed.
Three outside key antennas are installed on the vehicle: the outside key antenna RH, the outside key antenna LH and the outside key antenna rear bumper/fascia. Generally when the request switch is pressed, the BCM energizes only the respective door antenna.
NOTE: The driver and front passenger doors on some vehicles may not perform door lock/unlock operation when pressing the door lock/unlock request switch. If you confirm this concern on a vehicle, you can use the Signal Tech-II to check Intelligent Key and BCM function.
NOTE: The outside key antenna detection area of the door lock/unlock function is approximately 31.50 in (80 cm) surrounding the driver and passenger door handles (1) and back door handle (2). However, the operating range depends on ambient conditions and the intelligent key battery strength.
SERVICE PROCEDURE
Using Signal Tech-II (J-50190), check/test the signals from the BCM and the Intelligent Key.
1. From outside the vehicle, lock the vehicle (lock all doors).
2. Select “Key Test” on the Signal Tech-II.
3. Hold Signal Tech-II and the Intelligent Key near a front door handle.
NOTE: Do not press the buttons on the I-Key.
4. Repeatedly press the request switch (on the door handle) and observe the signal response outputs (relative signal strength) on the Signal Tech-II.
SIGNAL RESPONSE FROM CAR ONLY
If there is a signal response from only the Car as shown here, first try replacing the Intelligent Key battery, then if necessary, replace the Intelligent Key. Refer to the CONSULT-III plus operation manual on the CONSULT PC for the replacement procedure for new Intelligent Key registration. For initialization and registration of the Intelligent Key, refer to the CONSULT Immobilizer mode and follow the on-screen instructions.
WEAK SIGNAL RESPONSE FROM I-KEY
If the signal response from the Intelligent Key is weak (it only moves a small additional amount on the bar graph when the request switch is pressed), the Intelligent Key battery may be weak. Refer to ITB09-059 for how to replace the Intelligent Key battery.
NOTE: If there is a small amount of signal shown on the Key bar graph, it is indicating a constant background RF is being detected; this is not a signal from the Intelligent Key. Refer to the example of a signal from an Intelligent Key.
NO SIGNAL RESPONSE FROM CAR OR I-KEY
If there is no signal response from the Car or the I-Key, perform a CONSULT function test via CAN communication with the BCM and on the sensors, harnesses or other parts that may be the possible root cause. Refer to the Electronic Service Manual (ESM), section BCS–Body Control System, for information on checking BCM function.
INTELLIGENT KEY REGISTRATION
Perform system initialization when replacing the BCM, replacing an Intelligent Key or registering an additional Intelligent Key. The ID registration is a procedure that erases the current NVIS (NATS) ID once, and then re-registers a new ID. Therefore, before starting the registration operation, collect all registered Intelligent Keys from the customer for his or her vehicle. Before registering a new key to a BCM, you must re-register all the I-Keys the customer supplied first, and then register the new I-Key to the vehicle (in that order).