Multiplex Control System: Other Infiniti Q45 II

BODY CONTROL MODULE (BCM)

The BCM, a master unit of the multiplex control system, has communication and control capabilities. The BCM consists of a microprocessor, memory and communication LSI sections. The BCM processes data signals received from the LCUs and sends electrical load data signals to each LCU.

LOCAL CONTROL UNIT (LCU)

The LCU is a slave unit of the BCM and has communication capability only. The LCU consists of communication LSI and input/output interface circuits. The LCU uses data signals from BCM to control on/off operation of electrical loads. The LCU also sends a switch signal to BCM to control on/off operation of sleep/wake-up control mode.

SLEEP/WAKE-UP CONTROL MODE

Note. Wake-up control mode can only be diagnosed using Nissan CONSULT scan tool.

The sleep/wake-up control mode allows the communication between BCM and LCUs to be turned on and off as necessary to prevent unnecessary power consumption. When BCM detects the following conditions, it will shut off communication with all LCUs and activate sleep mode after about 30 seconds: ignition off, electrical loads off, timer off and vehicle speed at zero MPH.

Communication with all LCUs will be re-established (system in normal control mode) if BCM detects a wake-up signal from the data line to LCUs, or if a change in ignition switch status is detected. The BCM will also re-establish communication with all LCUs if it detects an "on" signal from one of the following switches, which are directly connected to BCM.

1. Key Switch
2. Ignition Switch (ACC Or ON)
3. Headlight Switch (First Detent)
4. Door Switch
5. Multi-Remote Controller
6. Trunk Compartment Light Switch
7. Engine Hood Switch
8. Door Or Trunk Key Cylinder Switch (UNLOCK)
9. Steering Tilt Switch
10. Steering Telescopic Switch

FAIL-SAFE CONTROL MODE

Fail-safe system operates when a signal from LCU is determined to be malfunctioning by BCM. If LCU sends no signal, or sends an abnormal signal to BCM a predetermined amount of times consecutively, system will set LCU in fail-safe condition. During fail-safe condition, all electrical loads controlled by the switch on the questionable LCU will operate in fail-safe mode.

Without Nissan CONSULT San Tool

To clear codes, turn ignition switch to LOCK position. Remove fuse No. 14 (7.5-amp) located instrument panel fuse box. Install fuse. Retrieve all codes to ensure procedure was successful.

MODE II (SWITCH SIGNAL MONITOR)

Note. This procedure is used to test switch signal inputs to BCM and LCUs without using Nissan CONSULT scan tool.

Scheme 3

1. In this mode, BCM and LCUs monitor respective switches in LAN system for input signals. Switch input signals are monitored in the following order. Body Control Module (BCM) Headlight Switch (First Detent) Headlight Switch (AUTO Position) Wiper Switch (INT Function) Wiper Switch (WASH Function) Door Switches (All) Rear Window Defogger Switch Detention Switch Seat Belt Switch (Driver's Side) Trunk Compartment Light Switch Hood Switch Trunk Lid Key Cylinder Switch (UNLOCK) Steering Tilt Switch (UP/DOWN) Steering Telescopic Switch (Forward/Backward) Auto Drive Positioner Cancel Switch Seat Memory Switches No. 1 and 2 Seat Set Switch Multi-Remote Controller Switch LCU 01 (Driver's Door Control Unit) Power Window Lock Switch Power Window Main Switch (UP/DOWN) Power Window Automatic Switch Door Lock & Unlock Switch (LOCK/UNLOCK) Door Unlock Sensor LCU 02 (Passenger's Door Control Unit) Door Unlock Sensor Right Front Power Window Sub-Switch (UP/DOWN) LCU 03 (Right Rear Door Control Unit) Door Unlock Sensor Right Rear Power Window Sub-Switch (UP/DOWN) LCU 04 (Left Rear Door Control Unit) Door Unlock Sensor Left Rear Power Window Sub-Switch (UP/DOWN) LCU 05 (Driver's Seat Control Unit) Slide Switch (FORWARD/BACKWARD) Reclining Switch (FORWARD/BACKWARD) Front Lifter Switch (UP/DOWN) Rear Lifter Switch (UP/DOWN)
2. To enter on-board diagnostic Mode II, turn ignition switch to LOCK position. Turn headlight switch and rear window defogger switch to OFF position. Ensure all doors are closed. Set interior light switch in center AUTO position. Set driver and passenger-side map light switches to OFF position. Place gear selector lever in Park.
3. Turn ignition switch to RUN position, then ACC position. Repeatedly press rear window defogger switch to ON position more than 10 times in 10 seconds, ending in the ON position. Dome and step lights should illuminate. Turn ignition switch to RUN position within 5 seconds after dome and step lights illuminate.
4. Dome and step lights should turn off, and within one second, system should enter on-board diagnostic Mode II. Operate the switches listed above. Dome and step lights will illuminate and buzzer will sound each time input signal from a switch is detected. (Scheme 3) To exit diagnostic mode, turn ignition switch to LOCK position or drive vehicle at a speed greater than 4 MPH.

SYSTEM TESTS

Note. If self-diagnostics produced multiple DTCs or fault messages, proceed to appropriate diagnostic test that contains the specified multiple faults. See WIRING DIAGRAMS to aid in wire color and wire terminal identification and/or component location.

Turn ignition switch to LOCK position. Disconnect BCM harness connector. Ensure battery voltage exists at appropriate terminal at BCM harness connector with ignition switch in appropriate position. See BCM POWER SUPPLY CIRCUIT CHECK table. (Scheme 4) If voltage is not as specified with ignition switch in appropriate position, repair power distribution circuit(s) as necessary. See WIRING DIAGRAMS.

BCM POWER SUPPLY CIRCUIT CHECK

Local Control Units (LCUs)

Turn ignition switch to LOCK position. Disconnect appropriate LCU harness connector. Ensure battery voltage exists at appropriate terminal at LCU harness connector with ignition switch in all positions. See LCU POWER SUPPLY CIRCUIT CHECK table. (Scheme 5), (Scheme 6) or (Scheme 7). If voltage is not as specified with ignition switch in appropriate position, repair power distribution circuit(s) as necessary. See WIRING DIAGRAMS.

LCU POWER SUPPLY CIRCUIT CHECK

Scheme 4

Scheme 5

Scheme 6

Scheme 7

Turn ignition switch to LOCK position. Disconnect BCM harness connector. Check for continuity between ground and terminals No. 56 (Black wire) and No. 113 (Black wire) at BCM harness connector. (Scheme 4) If continuity exists, ground circuit is okay at this time. If continuity does not exist, repair open in Black wire between BCM and ground.

Turn ignition switch to LOCK position. Disconnect appropriate LCU harness connector. Check for continuity between ground and appropriate terminal at LCU harness connector. See LCU GROUND CIRCUIT CHECK table. (Scheme 5), (Scheme 6) or (Scheme 7). If continuity exists, ground circuit is okay at this time. If continuity does not exist, repair open in Black wire between appropriate LCU and ground.

LCU GROUND CIRCUIT CHECK