four wheel drive MAZDA 6 2002 Workshop Manual Suplement

M–8
ELECTRONIC 4WD CONTROL SYSTEM
Components and Functions
System Diagram
.
Part name Function
Electronic control coupling
(4WD solenoid)•Based on a signal from the 4WD CM, it operates the electromagnetic clutch and
transmits drive torque to the rear wheels.
Differential oil temperature
sensor•Informs the 4WD CM of the rear differential oil temperature.
4WD CM•Controls operation of the electronic control coupling (4WD solenoid) based on signals
input from the throttle opening angle, speed, differential oil temperature and other
sensors.
•Outputs coupling control condition and 4WD warning control information as a CAN
signal.
•Controls the on-board diagnostic system and the fail-safe system if there is a malfunction
in the 4WD system.
4WD warning light•Illuminates or flashes to alert driver of a malfunction or control failure in the 4WD system.
PCM•Sends the throttle opening angle and engine speed signals, as CAN signals, to the 4WD
CM.
TCM•Sends the selector lever position and gear position signals, as CAN signals, to the 4WD
CM.
DSC HU/CM•Sends the four-wheel speed and DSC operating condition signals, as CAN signals, to the
4WD CM.
•Sends the coupling torque request signal, as a CAN signal, to the 4WD CM.
KO
P I
A
C
NH G
9
8
7
5
4
3
10
13
11
12
6
1
2
A6E63222002
1 Battery
2 Ignition switch
3 Differential oil temperature sensor
4 4WD control modure (4WD CM)
5 Electronic control coupling
6 4WD solenoid
7 Instrument cluster8 DSC HU/CM
9TCM
10 PCM
11 CAN-H
12 CAN-L
13 CAN driver

ELECTRONIC 4WD CONTROL SYSTEM
M–13
M
4WD CONTROL MODUREA6E632227100205Function
•The 4WD control modure (4WD CM) calculates the optimal amount of torque distribution for the rear wheels
and outputs a corresponding electric current to the electronic control coupling (4WD solenoid). This calculation
is based on the throttle angle, four-wheel speed, engine speed, selector lever position, and other related input
signals, matched with the vehicle driving and road surface conditions.
Functions
Construction
•The 4WD CM is installed to the left of the brake pedal (clutch pedal position).
Block diagram
.
Function name Contents
4WD system control
function•Based on each input signal, the electronic control current sent to the electronic control coupling
(4WD solenoid) is optimally controlled.
Diagnostic system•If the self-diagnostic system detects a malfunction, the 4WD warning light illuminates to alert
the driver, and at the same time the system suspends control or performs other measures to
prevent a loss of driving stability and protect the system.
•The detected malfunction is stored as a DTC in the 4WD CM.
987
5
43
10
19
18
17
15
16
14
131112
6
1
2
A6E63222008
1Front
2PCM
3TCM
4 DSC HU/CM
5 4WD control modure (4WD CM)
6 4WD solenoid
7Transaxle
8Transfer
9 Propeller shaft
10 Front drive shaft11 Pilot clutch/pilot cam
12 Ball/main cam
13 Main clutch
14 Electronic control coupling
15 Rear differential
16 Rear drive shaft
17 Torque transmission path
18 Electric signal path
19 Solenoid activation

ELECTRONIC 4WD CONTROL SYSTEM
M–15
M
Operation
Normal control
•When starting off or accelerating during straight-ahead driving, torque transmitted to the rear wheels is
optimally controlled to ensure sufficient acceleration performance. Due to this, standing-start and acceleration
performance is improved.
•Also, in order to improve fuel economy when driving at a stable, consistent speed, torque transmitted to the
rear wheels is damped, and rear-wheel drive is controlled to maintain it close to that of the front wheels.
Tight cornering control
•When the 4WD CM determines, based on the four-wheel speed signal, that the vehicle is in tight cornering, it
reduces the torque transmitted to the rear wheels to avoid tight corner braking characteristics.
Integrated DSC control
•If a signal from the DSC HU/CM input to the 4WD CM indicates that ABS control is activated, the module
controls the torque transmitted to the rear wheels to prevent undue influence on ABS control.
•Also, when a coupling torque request signal is received from the DSC HU/CM, the module controls the torque
transmitted to the rear wheels to match the amount of requested torque.
Other control
•In case the rear differential oil temperature exceeds the specified amount, or when there is an unusually large
variation in the rotation speed of the front and rear wheels (ex. when trying to get unstuck), control is
temporarily suspended in order to protect the 4WD system. When this occurs the 4WD warning light flashes to
indicate the situation to the driver.
End Of Sie
CONTROLLER AREA NETWORK (CAN)A6E632227100207Outline
•The 4WD CM transmits/receives information using the CAN system. See Section T for detailed information
regarding the CAN system.
Operation
Transmitted information
•Coupling torque
•4WD system operating condition (warning light information)
Received information
•Four-wheel speed
•Throttle opening angle
•Engine speed
•ABS/DSC operating condition
•Gear position
•Selector lever position
•Coupling torque request
End Of Sie

M–80
ON-BOARD DIAGNOSTIC
End Of Sie
DTC U0100A6E637027100205
Diagnostic Procedure
•Inspect according to the diagnostic procedure in Section T. (See T–39 MULTIPLEX COMMUNICATION
SYSTEM.)
End Of Sie
DTC U0101A6E637027100206
Diagnostic Procedure
•Inspect according to the diagnostic procedure in Section T. (See T–39 MULTIPLEX COMMUNICATION
SYSTEM.)
End Of Sie
DTC U0121A6E637027100207
Diagnostic Procedure
•Inspect according to the diagnostic procedure in Section T. (See T–39 MULTIPLEX COMMUNICATION
SYSTEM.)
End Of Sie
4INSPECT 4WD CM TO DIFFERENTIAL OIL
TEMPERATURE SENSOR FOR SHORT TO
GROUND
•Inspect for continuity between 4WD CM
terminal A and ground.
•Is there continuity?Yes Repair or replace harness for short to ground between 4WD
CM and differential oil temperature sensor, then go to Step
7.
No Go to next step.
5INSPECT 4WD CM TO DIFFERENTIAL OIL
TEMPERATURE SENSOR FOR OPEN
CIRCUIT
•Inspect for continuity between 4WD CM
terminal C and differential oil temperature
sensor terminal B.
•Is there continuity?Yes Go to next step.
No Repair or replace harness for open circuit between 4WD CM
and differential oil temperature sensor, then go to Step 7.
6INSPECT 4WD CM TO DIFFERENTIAL OIL
TEMPERATURE SENSOR FOR SHORT TO
GROUND
•Inspect for continuity between 4WD CM
terminal C and ground.
•Is there continuity?Yes Repair or replace harness for short to ground between 4WD
CM and differential oil temperature sensor, then go to next
step.
No Replace 4WD CM, then go to next step.
7VERIFY TROUBLESHOOTING COMPLETED
•Make sure to reconnect all disconnected
connectors.
•Clear DTC from memory.
(See M–76 Clearing DTCs Procedures)
•Drive vehicle.
•Is the same DTC present?Yes Replace 4WD CM, then go to next step.
No Go to next step.
8VERIFY AFTER REPAIR PROCEDURE
•Is there any other DTC present?Yes Go to applicable DTC inspection.
No Troubleshooting completed. STEP INSPECTION ACTION
DTC U0100 PCM communication
DETECTION
CONDITION•4WD CM detects that communication signals (throttle opening angle and engine speed signals) from
PCM are abnormal.
POSSIBLE
CAUSE•PCM signals have communication error.
DTC U0101 TCM communication
DETECTION
CONDITION•4WD CM detects that communication signals (selector lever position and gear position signals) from
TCM are abnormal.
POSSIBLE
CAUSE•TCM signals have communication error.
DTC U0121 ABS/DSC communication
DETECTION
CONDITION•4WD CM detects that communication signals (four-wheel speed, ABS/DSC operation condition, and
coupling torque request signals) from DSC HU/CM are abnormal.
POSSIBLE
CAUSE•DSC HU/CM signals have communication error.

P–8
DYNAMIC STABILITY CONTROL
End Of SieCOMBINE SENSOR (FORWARD-G SENSOR)A6E692067650202Function
•The forward-G sensor is integrated with the combine sensor to detect and calculate the vehicle forward-G force
and change in voltage to the DSC HU/CM.
Structure/Operation
•The drive train of 4WD vehicles delivers driving force to all four wheels, and due to this interlocking, the speed
of all wheels during braking is the same. When driving on road surfaces with especially low m (friction
coefficient), it is difficult to estimate the vehicle speed based on the wheel speed, and DSC braking becomes
unreliable. (For 2WD vehicles, the front and rear wheels are independent, so it is possible to accurately
estimate the vehicle speed by measuring the difference between the rotation speeds of the front and rear tires.)
A forward-G sensor has been installed to overcome this situation. When braking, the change in G-force is
detected, and the road surface m is judged (low m, high m), enabling a correction of the vehicle speed
estimation.
•The output voltage characteristic for the combine sensor is 2.5 V when the vehicle is standing still, and
changes accordingly as forward-G is formed.
•Forward-G is formed when the sensor detects an inertial force created by, and in proportion to, a G- force
acting on a silicon detection component.
.
End Of Sie
CONTROLLER AREA NETWORK (CAN)A6E692067650203•ABS (ABS/TCS) or DSC HU/CM transmit/receive information through CAN. Due to the addition of TCM, 4WD
CM, and the MZR-CD (RF Turbo) engine model, the following information has been changed. For detailed
information on CAN, see the “CONTROLLER AREA NETWORK.” (See T–3 OUTLINE.)
Transmitted Information
•Coupling torque request (to 4WD CM)
•DSC operating condition (to 4WD CM)
Received Information
•Coupling torque (from 4WD CM)
•Shift position (from TCM)
•Fuel injection information (only MZR-CD (RF Turbo), from PCM)
End Of Sie
(V)
2.5
-14.70
+14.7(m/s
2)
45
3
6
2
1
A6E6920W201
1 External view
2 Front of vehicle
3 Output voltage characteristic4 Deceleration
5 Forward-G
6 Acceleration