Transfer Case - Mp 3010-NP0: Overview GMC Yukon III

Circuit/System Description

The all wheel drive (AWD) indicator circuit consists of a light emitting diode (LED), a LED feed circuit and a LED control circuit. The indicator dimming control circuit is the LED feed circuit and continuously supplies voltage to the 2 High, Auto 4WD, 4 Low and 4 High LEDs. When the AWD mode has been selected by the driver, the transfer case shift control module (TCCM) provides a ground through the AWD indicator control circuit illuminating the LED. The TCCM tests the AWD indicator circuit for unexpected voltage by monitoring the B+ supplied by the BCM on the indicator dimming control circuit, by grounding the AWD indicator control circuit for 2 seconds during the bulb test at key ON.

The 4 High indicator circuit consists of a light emitting diode (LED), a LED feed circuit and a LED control circuit. The indicator dimming control circuit is the LED feed circuit and continuously supplies voltage to the 2 High, Auto 4WD, and 4 High LEDs. When the 4 High mode has been selected by the driver, the transfer case shift control module (TCCM) provides a ground through the 4 High indicator control circuit illuminating the LED. The TCCM tests the 4 High indicator circuit for unexpected voltage by monitoring the B+ supplied by the BCM on the indicator dimming control circuit by grounding the 4 High indicator control circuit for 2 seconds during the bulb test at key ON.

The 2 High indicator circuit consists of a light emitting diode (LED), a LED feed circuit and a LED control circuit. The indicator dimming control circuit is the LED feed circuit and continuously supplies voltage to the 2 High, Auto 4WD, and 4 High LEDs. When the 2 High mode has been selected by the driver, the transfer case shift control module (TCCM) provides a ground through the 2 High indicator control circuit illuminating the LED. The TCCM tests the 2 High indicator circuit for unexpected voltage by monitoring the B+ supplied by the BCM on the indicator dimming control circuit by grounding the 2 High indicator control circuit for 2 seconds during the bulb test at key ON.

The transfer case shift control switch (TCSCS) has 3 modes. The transfer case shift control module (TCCM) supplies a regulated 5 V DC to the switch through the 5-volt reference circuit. The current travels through the specific resistor of the currently selected mode, each mode has its own resistor. The current is then returned to the TCCM through the switch signal circuit.

The TCCM continuously monitors the switch signal circuit to determine whether a mode change has been requested by the driver.

The NP0 transfer case has the following 3 modes

1. 2 Hi
2. 4WD Auto
3. 4 Hi

The transfer case encoder motor (TCEM) is a bi-directional, permanent magnet, DC motor. When energized, through motor control A or motor control B, the ground is provided by the opposing motor control circuit and then grounded through the transfer case shift control module (TCCM) ground circuit, the TCEM, through a series of gears, rotates the transfer case control actuator shaft which moves the transfer case two/four wheel drive actuator cam and transfer case high/low shift fork to shift the transfer case between the following modes or ranges

1. 2WD HI
2. 4WD Auto
3. 4WD HI

The transfer case shift control module controls the transfer case lock solenoid.

The transfer case lock solenoid is released by being energized. This is accomplished by grounding the lock solenoid control circuit during mode shifts, and 4WD Auto mode. Locking action is applied when power or ground are taken away from the lock solenoid, the transfer case motor is prevented from moving. The system is capable of providing a 2WD HI, 4WD Auto, or 4WD HI lock-up without the need of additional vehicle power to hold the transfer case in these positions.

This DTC detects an open lock solenoid coil, open motor lock control circuit, or an open battery positive voltage circuit, or a short to voltage or ground on the lock solenoid control circuit.

The general system performance DTC sets based on a thermal module within the transfer case shift control module (TCCM) software. The components included in this thermal model are the motor driver within the TCCM, the shift motor, and the clutch inside the transfer case.

This fault occurs when one of the three components included in the thermal model surpass the upper limits of this model indicating possible damage to the transfer case or other driveline components. This DTC detects an over temperature condition base on a thermal model.

The front axle control circuit consists of an electric motor actuator which engages and disengages the front axle. The front axle actuator motor consists of a permanent magnetic motor, a worm gear controlled plunger, a front axle switch and an electronic control circuit within the actuator assembly.

The front axle actuator consists of the following circuits

1. An Ignition 1 voltage circuit
2. An axle switch signal circuit
3. An axle actuator control circuit
4. A ground circuit

When a shift to 4WD Auto or 4WD HI is requested, the transfer case shift control module (TCCM) engages the front axle by grounding the front axle control circuit through a current limiting driver.

The transfer case encoder motor (TCEM) is a bi-directional, permanent magnet, DC motor. When energized, through motor control A or motor control B, the ground is provided by the opposing motor control circuit and then grounded through the transfer case shift control module (TCCM) ground circuit, the TCEM, through a series of gears, rotates the transfer case control actuator shaft which moves the transfer case two/four wheel drive actuator cam and transfer case high/low shift fork to shift the transfer case between the following modes or ranges

1. 2WD HI
2. 4WD Auto
3. 4WD HI

If the shift lever detent shaft were to bind, or there was a mechanical failure, or motor A control and motor B control were shorted together, the shift would not be completed. This will cause the DTC to set in order to protect system components from damage.

The transfer case shift control module (TCCM) receives input from the transfer case two/four wheel drive actuator position sensor, also known as the rotational position sensor (RPS). The RPS receives a 5-volt reference signal from the TCCM. In return the RPS sends the TCCM a variable pulse width modulated signal indicating the position of the transfer case actuator. The RPS works in conjunction with the incremental position sensor, inside the transfer case actuator, to confirm actuator position. The RPS is more sensitive than the incremental position sensor and is able to indicate to the TCCM the exact position of the transfer case actuator between modes or ranges changes. It is also able to show how much clutch activation is being commanded at any time.

The transfer case incremental position sensor (IPS) and the transfer case rotational position sensor (RPS) both send current transfer case mode/range position to the transfer case shift control module (TCCM). Both sensors send this information as voltage signals which are converted to degrees and rotational direction by the TCCM software. If the two sensors disagree by greater than a predetermined amount, the DTC will set.

The IPS receives an 8 volt reference signal from the TCCM and sends back a transfer case incremental position signal and an encoder rotational direction signal.

The RPS (also known as the transfer case two/four wheel drive actuator position sensor) receives a 5 volt reference signal from the TCCM and sends back a continuously variable pulse width modulated signal to the TCCM. This continuously variable signal indicates the position of the transfer case actuator.

The IPS is more sensitive than the RPS, but needs to reference the RPS value at key-up and mode changes. The RPS is an absolute sensor. The TCCM syncs the IPS with the RPS at key-up and mode changes.

The IPS is an integral part of the transfer case actuator and cannot be replaced independently.

The RPS is an independently replaceable part.

In 4WD Auto mode, the transfer case shift control module (TCCM) monitors the front and rear wheel speed sensors for slip. If the TCCM detects slip, and is unable to correct for a difference between the front and rear speed sensors, it will command the transfer case to apply the clutch.

The transfer case incremental position sensor (IPS) and the transfer case two/four wheel drive actuator position sensor, also known as the rotational position sensor (RPS), both send transfer case mode/range position information to the transfer case shift control module (TCCM). Both sensors send this information as voltage signals which are converted to degrees by the TCCM software. If the two sensors disagree by greater than a predetermined amount the DTC will set.

The IPS is more sensitive than the RPS, but needs to reference the RPS value at key-up and mode changes. The IPS is an integral part of the transfer case actuator and cannot be replaced independently.

The RPS is an absolute sensor and is an independently replaceable part. The TCCM syncs the IPS with the RPS at key-up and mode changes.

This is an internal fault detection of the transfer case shift control module (TCCM). This fault is handled inside the TCCM. No external circuits are involved.

At each power-up, the TCCM runs a self-test on the following

1. EEPROM Checksum
2. ROM Checksum
3. RAM Checksum
4. RAM Malfunction

1. This is an internal fault detection of the transfer case shift control module (TCCM). No external circuits are involved.
2. This DTC is set anytime a TCCM is replaced or reprogrammed.
3. The automatic transfer case (ATC) motor learn procedure must be performed to erase this DTC. The motor learn procedure allows the module to learn where the shift rails are located.

The transfer case shift control module (TCCM) monitors the battery voltage feed to the TCCM. This DTC detects if the battery voltage is out of range. This could indicate a vehicle wide issue in which all electrical components would be affected, or it could be TCCM specific due to poor power or ground connections.

The vehicle speed sensor (VSS) provides vehicle speed information to the engine control module (ECM). The VSS is a permanent magnet generator. The sensor is mounted in the transfer case facing the rear internal gear which is splined to the output shaft assembly. As the output shaft and internal gear rotate, the toothed rotor of the internal gear produces AC voltage as the rotor teeth pass through the magnetic field of the sensor. The AC voltage level and the number of pulses increase as the speed of the vehicle increases. The ECM converts the voltage to vehicle speed. The ECM uses the output shaft speed signal to determine shift timing, as well as transfer case range.

The front axle control circuit consists of an electric motor actuator which engages and disengages the front axle. The front axle actuator motor consists of a permanent magnetic motor, a worm gear controlled plunger, a front axle switch and an electronic control circuit within the actuator assembly.

The front axle actuator consists of the following circuits

1. The front axle control circuit, which is also connected to the transfer case shift control module
2. The front axle switch circuit, which is also connected to the transfer case shift control module
3. An ignition 3 voltage circuit
4. A ground circuit

When a shift to AUTO 4WD, 4HI, or 4LO is requested, the transfer case shift control module engages the front axle by grounding the front axle control circuit through a current limiting driver.

The front axle control circuit consists of an electric motor actuator which engages and disengages the front axle. The front axle actuator motor consists of a permanent magnetic motor, a worm gear controlled plunger, a front axle switch and an electronic control circuit within the actuator assembly.

The front axle actuator consists of the following circuits

1. The front axle control circuit, which is also connected to the transfer case shift control module
2. The front axle switch circuit, which is also connected to the transfer case shift control module
3. An ignition 3 voltage circuit
4. A ground circuit

When a shift to AUTO 4WD, 4HI, or 4LO is requested, the transfer case shift control module engages the front axle by grounding the front axle control circuit through a current limiting driver.

The active transfer case mode switch circuit consists of 5 modes. The transfer case shift control module supplies 5 volts to the switch through the 5-volt reference circuit. The current travel through the resistor of the currently active mode. The current is then returned to the transfer case shift control module through the switch signal circuit.

The transfer case shift control module constantly monitors this signal voltage to determine the condition of the mode switch circuit.

When each of the modes are selected they complete a circuit through their own specific resistor. The transfer case shift control module continuously monitors the switch input to determine whether the Neutral, AWD, 2HI, 4HI, or 4LO mode was selected by the driver.

When transfer case is in auto 4WD mode the transfer case control module monitors the front wheel speeds and the rear wheel speeds. When a noticeable difference between the front and rear is seen the transfer case control module sends a PWM voltage to the motor so it can apply the clutch in order to correct a slip condition. The slip conditions is the difference in speed between the front and rear axles. The module has a thermal model based system so when the slip correction can not be made when a large percentage PWM signal has been sent, it will disable the system to prevent damage to the clutches.

The indicator circuits consists of an interior lights dimming circuit and an indicator control circuit. When a mode has been selected, current is supplied to the indicator by the interior lights dimming circuit, traveling through the indicator LED, at which time the transfer case shift control module supplies the ground through the indicator lamp control circuit.

The indicator circuits consists of an interior lights dimming circuit and an indicator control circuit. When a mode has been selected, current is supplied to the indicator by the interior lights dimming circuit, traveling through the indicator LED, at which time the transfer case shift control module supplies the ground through the indicator lamp control circuit.

If the service indicator needs to be turned on the transfer case shift control module sends a signal via LAN to the instrument panel asking the I/P to command the Service 4WD indicator.

Transfer Case Description and Operation

The Magna Powertrain (MP) model 3010 RPO NP0 transfer case is a 1 speed automatic, active transfer case (ATC). The MP 3010 ATC provides 3 modes, Auto 4WD, 4HI, and 2HI. The Auto 4WD position allows the capability of an active transfer case, which provides the benefits of on-demand torque biasing wet clutch and easy vehicle tuning through software calibrations. The software calibrations allow more features, such as flexible adapt ready position and clutch preload torque levels. The technology allows for vehicle speed dependent clutch toque levels to enhance the performance of the system. For example, the system is calibrated to provide 0-6.78N.m (0-5 lb ft) of clutch torque during low speed, low engine torque operation, and predetermined higher torque for 40 km/h (25 mph) and greater. This prevents crow-hop and binding at low speeds and provides higher torque biases at higher vehicle speeds, in order to enhance stability.

Scheme 1

The MP 3010 ATC transfer case features a 3 mode shift control switch located on the instrument panel. When the ignition key is in the RUN position, the transfer case shift control module monitors the transfer case shift control switch to determine if the driver desires a new mode position. At a turn of the transfer case shift control switch, the lamp of the new desired position begins flashing to inform the driver that the transfer case shift control module has received the request for a new mode position. The lamp continues to flash until all shifting criteria has been met and the new mode position has been reached, or has been engaged. Once the mode position is fully active, the switch indicator lamp for the new position remains ON constantly. During normal driving situations, the transfer case can operate in the Auto 4WD mode. In the Auto 4WD mode, the transfer case shift control module monitors rear wheel slip speed, based on the inputs from the wheel speed sensors and/or vehicle speed sensor. When the vehicle experiences a rear wheel slip condition, the transfer case shift control module sends a pulse width modulated (PWM) signal to an electronic motor, which is the transfer case 2/4 wheel drive actuator assembly. This actuator rotates the transfer case control actuator shaft, applying a clutch. The clutch is designed to deliver a variable amount of torque, normally delivered to the rear wheels, and transfers it to the front wheels. Torque is ramped up to the front wheels until the front wheels speed sensor values equals that of the rear wheel speed sensors and/or vehicle speed sensor. Torque is ramped down to the front wheels. The process would repeat if rear wheel slip is detected again.

The MP 3010 TC transfer case has the added feature of also providing the driver with 2 manual mode positions

1. 4HI -4 Wheel Drive High Mode
2. 2HI - 2 Wheel Drive High Mode

Scheme 2

Scheme 3

When the MP 3010 ATC is in the 2WD mode, the power flows from the transmission (1) to the input shaft (2). The input shaft (2) is splined to the rear output shaft (3). The rear output shaft (3) delivers the power flow to the rear propshaft (4). The position of the control actuator shaft (6) allows no clutch (5) engagement.

Scheme 4

Scheme 5

In the 4HI mode, the power flow to the rear propshaft (9) is the same as it is in the 2WD mode. To deliver power flow to the front propshaft (15) during the 4HI position, the transfer case control module commands the 2/4 wheel drive actuator assembly (13) to apply the clutch to a calibrated torque. The 2/4 wheel drive actuator assembly (13) turns the control actuator shaft. A brake in the 2/4 wheel drive actuator assembly (13) holds the control actuator shaft in the full clutch position. The control actuator shaft is cam designed and the cam action moves the control actuator lever (12). The control actuator lever (12) pivots against the control lever (17) and moves toward the clutch pressure plate (4), to engage the clutch (5). As more pressure is applied to the clutch pressure plate (4), the clutch discs (5) are compressed. Using inner clutch discs, which are engaged with the clutch hub, and the outer clutch discs, which are engaged with the clutch housing (6), the power flow is delivered to the clutch housing (6). The clutch hub is splined to the rear output shaft (8), and the clutch housing (6) rotates on a needle bearing on the rear output shaft (8). The chain drive sprocket (7) is splined to the clutch housing (6). The power flows from the drive sprocket (7), through the chain (10), to the chain driven sprocket. The driven sprocket is splined to the front output shaft (14). The power flow is delivered to the front propshaft (15) through the front output shaft (14).

Scheme 6

In the 4HI Auto mode, the power flow to the rear propshaft (9) is the same as it is in the 2WD mode. To deliver power flow to the front propshaft (15) during the 4HI position, the transfer case control module commands the 2/4 wheel drive actuator assembly (13) to apply the clutch to a calibrated torque. The 2/4 wheel drive actuator assembly (13) rotates the control actuator shaft to the correct torque level positions. Rotating the control actuator shaft to the various positions changes the clutch torque level. The control actuator shaft is cam designed and the cam action moves the control actuator lever (12). The control actuator lever (12) pivots against the control lever (17) and moves toward the clutch pressure plate (4), to engage the clutch (5). As more pressure is applied to the clutch pressure plate (4), the clutch discs (5) are compressed. Using inner clutch discs, which are engaged with the clutch hub, and the outer clutch discs, which are engaged with the clutch housing (6), the power flow is delivered to the clutch housing (6). The clutch hub is splined to the rear output shaft (8), and clutch housing (6) rotates on a needle bearing on the rear output shaft (8). The chain drive sprocket (7) is splined to the clutch housing (6). The power flows from the drive sprocket (7), through the chain (10), to the chain driven sprocket. The driven sprocket is splined to the front output shaft (14). The power flow is delivered to the front propshaft (15) through the front output shaft (14). When a difference of front wheel speed to rear wheel speed is recognized, the transfer case control module commands for more or less clutch torque.