Electronic Control Modules Dodge Pickup R1500

DESCRIPTION

The DaimlerChrysler Programmable Communication Interface (PCI) data bus system is a single wire multiplex system used for vehicle communications on many DaimlerChrysler Corporation vehicles. Multiplexing is a system that enables the transmission of several messages over a single channel or circuit. All DaimlerChrysler vehicles use this principle for communication between various microprocessor-based electronic control modules. The PCI data bus exceeds the Society of Automotive Engineers (SAE) J1850 Standard for Class B Multiplexing.

Many of the electronic control modules in a vehicle require information from the same sensing device. In the past, if information from one sensing device was required by several controllers, a wire from each controller needed to be connected in parallel to that sensor. In addition, each controller utilizing analog sensors required an Analog/Digital (A/D) converter in order to "read" these sensor inputs. Multiplexing reduces wire harness complexity, sensor current loads and controller hardware because each sensing device is connected to only one controller, which reads and distributes the sensor information to the other controllers over the data bus. Also, because each controller on the data bus can access the controller sensor inputs to every other controller on the data bus, more function and feature capabilities are possible.

In addition to reducing, wire harness complexity, component sensor current loads and controller hard-ware, multiplexing offers a diagnostic advantage. A multiplex system allows the information flowing between controllers to be monitored using a diagnostic scan tool. The DaimlerChrysler system allows an electronic control module to broadcast message data out onto the bus where all other electronic control modules can "hear" the messages that are being sent. When a module hears a message on the data bus that it requires, it relays that message to its microprocessor. Each module ignores the messages on the data bus that are being sent to other electronic control modules.

OPERATION

Data exchange between modules is achieved by serial transmission of encoded data over a single wire broadcast network. The wire colors used for the PCI data bus circuits are yellow with a violet tracer, or violet with a yellow tracer, depending upon the application. The PCI data bus messages are carried over the bus in the form of Variable Pulse Width Modulated (VPWM) signals. The PCI data bus speed is an average 10.4 Kilo-bits per second (Kbps). By comparison, the prior two-wire Chrysler Collision Detection (CCD) data bus system is designed to run at 7.8125 Kbps.

The voltage network used to transmit messages requires biasing and termination. Each module on the PCI data bus system provides its own biasing and termination. Each module (also referred to as a node) terminates the bus through a terminating resistor and a terminating capacitor. There are two types of nodes on the bus. The dominant node terminates the bus through a 1 KW resistor and a 3300 pF capacitor. The Powertrain Control Module (PCM) is the only dominant node for the PCI data bus system. A standard node terminates the bus through an 11 KW resistor and a 330 pF capacitor.

The modules bias the bus when transmitting a message. The PCI bus uses low and high voltage levels to generate signals. Low voltage is around zero volts and the high voltage is about seven and one-half volts. The low and high voltage levels are generated by means of variable-pulse width modulation to form signals of varying length. The Variable Pulse Width Modulation (VPWM) used in PCI bus messaging is a method in which both the state of the bus and the width of the pulse are used to encode bit information. A "zero" bit is defined as a short low pulse or a long high pulse. A "one" bit is defined as a long low pulse or a short high pulse. A low (passive) state on the bus does not necessarily mean a zero bit. It also depends upon pulse width. If the width is short, it stands for a zero bit. If the width is long, it stands for a one bit. Similarly, a high (active) state does not necessarily mean a one bit. This too depend upon pulse width. If the width is short, it stands for a one bit. If the width is long, it stands for a zero bit.

In the case where there are successive zero or one data bits, both the state of the bus and the width of the pulse are changed alternately. This encoding scheme is used for two reasons. First, this ensures that only one symbol per transition and one transition per symbol exists. On each transition, every transmitting module must decode the symbol on the bus and begin timing of the next symbol. Since timing of the next symbol begins with the last transition detected on the bus, all of the modules are re-synchronized with each symbol. This ensures that there are no accumulated timing errors during PCI data bus communication.

The second reason for this encoding scheme is to guarantee that the zero bit is the dominant bit on the bus. When two modules are transmitting simultaneously on the bus, there must be some form of arbitration to determine which module will gain control. A data collision occurs when two modules are transmitting different messages at the same time. When a module is transmitting on the bus, it is reading the bus at the same time to ensure message integrity. When a collision is detected, the module that transmitted the one bit stops sending messages over the bus until the bus becomes idle.

Each module is capable of transmitting and receiving data simultaneously. The typical PCI bus message has the following four components

1. Message Header - One to three bytes in length. The header contains information identifying the message type and length, message priority, target module(s) and sending module.
2. Data Byte(s) - This is the actual message that is being sent.
3. Cyclic Redundancy Check (CRC) Byte - This byte is used to detect errors during a message transmission.
4. In-Frame Response (IFR) byte(s) - If a response is required from the target module(s), it can be sent during this frame. This function is described in greater detail in the following paragraph. The IFR consists of one or more bytes, which are transmitted during a message. If the sending module requires information to be received immediately, the target module(s) can send data over the bus during the original message. This allows the sending module to receive time-critical information without having to wait for the target module to access the bus. After the IFR is received, the sending module broadcasts an End of Frame (EOF) message and releases control of the bus.

The PCI data bus can be monitored using the DRBIII(R) scan tool. It is possible, however, for the bus to pass all DRBIII(R) tests and still be faulty if the voltage parameters are all within the specified range and false messages are being sent.

The Controler Antilock Brake (CAB) is mounted to the Hydraulic Control Unit (HCU) and operates the ABS system (Scheme 1)

Scheme 1

The CAB voltage source is through the ignition switch in the RUN position. The CAB contains a self check program that illuminates the ABS warning light when a system fault is detected. Faults are stored in a diagnostic program memory and are accessible with the DRB III scan tool. ABS faults remain in memory until cleared, or until after the vehicle is started approximately 50 times. Stored faults are not erased if the battery is disconnected.

Note. If the CAB is being replaced with a new CAB is must be reprogrammed with the use of a DRB III.

REMOVAL

1. Remove the negative battery cable from the battery.
2. Pull up on the CAB harness connector release and remove connector.
3. Remove the CAB mounting bolts.
4. Remove the pump connector from the CAB.
5. Remove the CAB from the HCU.

INSTALLATION

Note. If the CAB is being replaced with a new CAB is must be reprogrammed with the use of a DRB III.

1. Install CAB to the HCU.
2. Install the pump connector to the CAB.
3. Install mounting bolts. Tighten to 2 N.m (16 in. lbs.).
4. Install the wiring harness connector to the CAB and push down on the release to secure the connector.
5. Install negative battery cable to the battery.

DESCRIPTION - DATA LINK CONNECTOR

The Data Link Connector (DLC) is located at the lower edge of the instrument panel near the steering column.

OPERATION - DATA LINK CONNECTOR

The 16-way data link connector (diagnostic scan tool connector) links the Diagnostic Readout Box (DRB) scan tool or the Mopar Diagnostic System (MDS) with the Powertrain Control Module (PCM).

DESCRIPTION - ECM

The engine control module (ECM) for the 5.9L Diesel engine is bolted to the left side of the engine below the intake manifold.

OPERATION - ECM

The main function of the Engine Control Module (ECM) is to electrically control the fuel system. The Powertrain Control Module (PCM) does not control the fuel system.

The ECM can adapt its programming to meet changing operating conditions. If the ECM has been replaced, flashed or re-calibrated, the ECM must learn the Accelerator Pedal Position Sensor (APPS) idle voltage. Failure to learn this voltage may result in unnecessary diagnostic trouble codes. Refer to ECM REMOVAL / INSTALLATION for learning procedures.

The ECM receives input signals from various switches and sensors. Based on these inputs, the ECM regulates various engine and vehicle operations through different system components. These components are referred to as ECM Outputs. The sensors and switches that provide inputs to the ECM are considered ECM Inputs.

Note. ECM Inputs

1. Accelerator Pedal Position Sensor (APPS) Volts
2. APPS1 Signal - For off engine APPS
3. APPS2 Signal - For off engine APPS
4. APPS idle validation switches #1 and #2
5. Battery Temperature
6. Battery voltage
7. Camshaft Position Sensor (CMP)
8. CCD bus (+) circuits
9. CCD bus (-) circuits
10. Crankshaft Position Sensor (CKP)
11. Data link connection for DRB scan tool
12. Engine Coolant Temperature (ECT) sensor
13. Fuel pressure sensor
14. Fan speed (engine cooling fan)
15. Ground circuits
16. Inlet air temperature sensor/pressure sensor
17. Intake air temperature sensor/MAP sensor
18. Oil Pressure switch
19. Power ground
20. Sensor return
21. Signal ground
22. Water-In-Fuel (WIF) sensor

Note. ECM Outputs

After inputs are received by the ECM, certain sensors, switches and components are controlled or regulated by the ECM. These are considered ECM Outputs. These outputs are for

1. CCD bus (+) circuits
2. CCD bus (-) circuits
3. CKP and APPS outputs to the PCM
4. Data link connection for DRB scan tool
5. Fan Clutch PWM
6. Five volt sensor supply
7. Fuel Control Actuator
8. Fuel transfer (lift) pump
9. Intake manifold air heater relays #1 and #2 control circuits
10. Malfunction indicator lamp (Check engine lamp) (databus)
11. Oil Pressure Swith/warning lamp (databus)
12. Wait-to-start warning lamp (databus)
13. Water-In-Fuel (WIF) warning lamp (databus)

The engine control module (ECM) is bolted to a support bracket near the fuel filter. The support bracket mounts to the block with four capscrews and vibration isolators. A ground wire is fastened to the bracket. The other end of the wire is fastened to the engine block.

Scheme 2

1. Record any Diagnostic Trouble Codes (DTC's) found in the ECM. To avoid possible voltage spike damage to the ECM, ignition key must be off, and both negative battery cables must be disconnected before unplugging ECM connectors.
2. Disconnect both negative battery cables at both batteries.
3. Remove the 50-way and 60-way connector bolts at the ECM. Note: The connector bolt is a female allen head. As bolt is being removed, very carefully remove connectors from the ECM.
4. Remove five ECM mounting bolts and remove ECM from the vehicle (Scheme 2)

Do not apply paint to ECM or a poor ground will result.

1. Position the ECM to the ECM support bracket and install the five mounting bolts. Tighten the bolts to 24 N.m (18 ft. lbs.).
2. Check pin connectors in ECM, 50-way and 60-way connectors for corrosion or damage. Repair as necessary.
3. Clean pins in the 50-way and 60-way electrical connectors with a electrical contact cleaner.
4. Install the 50-way and 60-way connectors to ECM. Tighten connector bolts to 3 N.m (27 in. lbs.).
5. Reconnect both negative battery cables.
6. Use DRBIII(R) scan tool to erase any stored companion DTC's from ECM.

The Front Control Module (FCM) is a micro controller based module located in the left front corner of the engine compartment. On this model the integrated power module must be positioned aside in order to access the front control module. The front control module mates to the power distribution center to form the Integrated Power Module (IPM). The integrated power module connects directly to the battery and provides the primary means of circuit protection and power distribution for all vehicle electrical systems. The front control module controls power to some of these vehicle systems electrical and electromechanical loads based on inputs received from hard wired switch inputs and data received on the PCI bus circuit (J1850).

For information on the Integrated Power Module Refer to INTEGRATED POWER MODULE .

As messages are sent over the PCI bus circuit, the front control module reads these messages and controls power to some of the vehicles electrical systems by completing the circuit to ground (low side driver) or completing the circuit to 12 volt power (high side driver). The following functions are Controlled by the Front Control Module

1. Headlamp Power with Voltage Regulation
2. Windshield Wiper "ON/OFF" Relay Actuation
3. Windshield Wiper "HI/LO" Relay Actuation
4. Windshield Washer Pump Motor
5. Fog Lamp Relay Actuation
6. Park Lamp Relay Actuation
7. Horn Relay Actuation

The following inputs are Received/Monitored by the Front Control Module

1. B+ Connection Detection
2. Power Ground
3. Ambient Temperature Sensing
4. Ignition Switch Run
5. Washer Fluid Level Switch
6. Windshield Wiper Park Switch
7. PCI Bus Circuit

DIAGNOSIS AND TESTING - FRONT CONTROL MODULE

The front control module is a printed circuit board based module with a on-board micro-processor. The front control module interfaces with other electronic modules in the vehicle via the Programmable Communications Interface (PCI) data bus (J1850). In order to obtain conclusive testing the Programmable Communications Interface (PCI) data bus, network and all of the electronic modules that provide inputs to, or receive outputs from the front control module must be checked. All PCI (J1850) communication faults must be resolved prior to further diagnosing any front control module related issues.

The front control module was designed to be diagnosed with an appropriate diagnostic scan tool, such as the DRB III(R). The most reliable, efficient, and accurate means to diagnose the front control module requires the use of a DRB III(R) scan tool and the proper Body Diagnostic Procedures manual.

Before any testing of the front control module is attempted, the battery should be fully charged and all wire harness and ground connections inspected around the affected areas on the vehicle.

1. Disconnect the positive and negative battery cables from the battery.
2. Partially remove the integrated power module from the engine compartment (Refer to «INTEGRATED POWER MODULE»(/dodge/pickup-r1500/1997-2012/remont/electrical-component-locations/#power-distribution) ).
3. Remove the front control module retaining screws.
4. Using both hands, pull the front control module straight from the integrated power module assembly to disconnect the 49-way electrical connector and remove the front control module from the vehicle.

1. Install the front control module on the integrated power module assembly by pushing the 49-way electrical connector straight in.
2. Install the front control module retaining screws. Torque the screws to 7 in. lbs.
3. Install the integrated power module (Refer to «INTEGRATED POWER MODULE»(/dodge/pickup-r1500/1997-2012/remont/electrical-component-locations/#power-distribution) ).
4. Connect the positive and negative battery cables.

The heated seat module is also known as the Seat Heat Interface Module. The heated seat module (Scheme 3) is located under the drivers front seat cushion, where it is secured to a mounting bracket. The heated seat module has a single connector receptacle that allows the module to be connected to all of the required inputs and outputs through the seat wire harness.

Scheme 3

The heated seat module is an electronic microprocessor controlled device designed and programmed to use inputs from the battery, the two heated seat switches and the two heated seat sensors to operate and control the heated seat elements in both front seats and the two heated seat indicator lamp Light-Emitting Diodes (LEDs) in each heated seat switch. The heated seat module is also programmed to perform self-diagnosis of certain heated seat system functions and provide feedback of that diagnosis through the heated seat switch indicator lamps.

The heated seat module cannot be repaired. If the heated seat module is damaged or faulty, the entire module must be replaced.

The heated seat module operates on fused battery current received from the integrated power module. Inputs to the module include a resistor multiplexed heated seat switch request circuit for each of the two heated seat switches and the heated seat sensor inputs from the seat cushions of each front seat. In response to those inputs the heated seat module controls battery current feeds to the heated seat elements and sensors, and controls the ground for the heated seat switch indicator lamps.

When a heated seat switch (Driver or Passenger) is depressed a signal is received by the heated seat module, the module energizes the proper indicator LED (Low or High) in the switch by grounding the indicator lamp circuit to indicate that the heated seat system is operating. At the same time, the heated seat module energizes the selected heated seat sensor circuit and the sensor provides the module with an input indicating the surface temperature of the selected seat cushion.

The Low heat set point is about 36° C (96.8° F), and the High heat set point is about 42° C (107.6° F). If the seat cushion surface temperature input is below the temperature set point for the selected temperature setting, the heated seat module energizes an N-channel Field Effect Transistor (N-FET) within the module which energizes the heated seat elements in the selected seat cushion and back. When the sensor input to the module indicates the correct temperature set point has been achieved, the module de-energizes the N-FET which de-energizes the heated seat elements. The heated seat module will continue to cycle the N-FET as needed to maintain the selected temperature set point.

If the heated seat module detects a heated seat sensor value input that is out of range or a shorted or open heated seat element circuit, it will notify the vehicle operator or the repair technician of this condition by flashing the High and/or Low indicator lamps in the affected heated seat switch. Refer to HEATED SEAT SYSTEM for flashing LED diagnosis and testing procedures. Refer to DIAGNOSIS AND TESTING HEATED SEAT MODULE in this section for heated seat module diagnosis and testing procedures.

DIAGNOSIS AND TESTING - HEATED SEAT MODULE

If a heated seat fails to heat and one or both of the indicator lamps on a heated seat switch flash, refer to HEATED SEAT SYSTEM for the location of flashing LED heated seat system diagnosis and testing procedures. If a heated seat heats but one or both indicator lamps on the heated seat switch fail to operate, test the heated seat switch. Refer to HEATED SEAT SYSTEM for heated seat switch diagnosis and testing procedures. If the heated seat switch checks OK, proceed as follows.

1. Check the heated seat element (Refer to «HEATED SEAT SYSTEM»(/dodge/pickup-r1500/1997-2012/remont/seats/#heated-seat-system) ).
2. Check the heated seat sensor (Refer to «HEATED SEAT SYSTEM»(/dodge/pickup-r1500/1997-2012/remont/seats/#heated-seat-system) ).
3. Check the heated seat switch (Refer to «HEATED SEAT SYSTEM»(/dodge/pickup-r1500/1997-2012/remont/seats/#heated-seat-system) ). NOTE: Refer to «HEATED SEAT SYSTEM»(/dodge/pickup-r1500/1997-2012/remont/seats/#heated-seat-system) for the location of complete heated seat system wiring diagrams and connector pin-out information.
4. Using a voltmeter, backprobe the appropriate heated seat module connector, do not disconnect. Check for voltage at the appropriate pin cavities. 12v should be present. If OK go to Step 5, if Not, Repair the open or shorted voltage supply circuit as required.
5. Using a ohmmeter, backprobe the appropriate heated seat module connector, do not disconnect. Check for proper continuity to ground on the ground pin cavities. Continuity should be present. If OK replace the heated seat module with a known good unit and retest system, if Not OK, Repair the open or shorted ground circuit as required.

1. Position the driver seat to the full rearward and inclined position.
2. Working under the driver front seat, remove the two heated seat module retaining screws. Due to the fact that the retaining screws are installed with the seat cushion pan removed, a small right angle screwdriver will be required to access and remove the screws.
3. Disconnect the seat wire harness connector from the connector receptacle on the back of the heated seat module. Depress the connector retaining tab and pull straight apart.
4. Remove the heated seat module from under the front seat.

1. Position the heated seat module under the front seat.
2. Connect the seat wire harness connector on the connector receptacle on the back of the heated seat module.
3. Working under the driver front seat, install the heated seat module retaining screws.
4. Re-position the driver seat.

DESCRIPTION - PCM

The Powertrain Control Module (PCM) is located in the right-rear section of the engine compartment under the cowl (Scheme 4)

Two different PCM's are used (JTEC and NGC). These can be easily identified. JTEC's use three 32-way connectors, NGC's use four 38-way connectors

Scheme 4

DESCRIPTION - MODES OF OPERATION

As input signals to the Powertrain Control Module (PCM) change, the PCM adjusts its response to the output devices. For example, the PCM must calculate different injector pulse width and ignition timing for idle than it does for wide open throttle (WOT).

The PCM will operate in two different modes

Open Loop and Closed Loop.

During Open Loop modes, the PCM receives input signals and responds only according to preset PCM programming. Input from the oxygen (O2S) sensors is not monitored during Open Loop modes.

During Closed Loop modes, the PCM will monitor the oxygen (O2S) sensors input. This input indicates to the PCM whether or not the calculated injector pulse width results in the ideal air-fuel ratio. This ratio is 14.7 parts air-to-1 part fuel. By monitoring the exhaust oxygen content through the O2S sensor, the PCM can fine tune the injector pulse width. This is done to achieve optimum fuel economy combined with low emission engine performance.

The fuel injection system has the following modes of operation

1. Ignition switch ON
2. Engine start-up (crank)
3. Engine warm-up
4. Idle
5. Cruise
6. Acceleration
7. Deceleration
8. Wide open throttle (WOT)
9. Ignition switch OFF

The ignition switch On, engine start-up (crank), engine warm-up, acceleration, deceleration and wide open throttle modes are Open Loop modes. The idle and cruise modes, (with the engine at operating temperature) are Closed Loop modes.

IGNITION SWITCH (KEY-ON) MODE

This is an Open Loop mode. When the fuel system is activated by the ignition switch, the following actions occur

1. The PCM pre-positions the idle air control (IAC) motor.
2. The PCM determines atmospheric air pressure from the MAP sensor input to determine basic fuel strategy.
3. The PCM monitors the engine coolant temperature sensor input. The PCM modifies fuel strategy based on this input.
4. Intake manifold air temperature sensor input is monitored.
5. Throttle position sensor (TPS) is monitored.
6. The auto shutdown (ASD) relay is energized by the PCM for approximately three seconds.
7. The fuel pump is energized through the fuel pump relay by the PCM. The fuel pump will operate for approximately three seconds unless the engine is operating or the starter motor is engaged.
8. The O2S sensor heater element is energized via the ASD or O2S heater relay. The O2S sensor input is not used by the PCM to calibrate air-fuel ratio during this mode of operation.

ENGINE START-UP MODE

This is an Open Loop mode. The following actions occur when the starter motor is engaged.

The PCM receives inputs from

1. Battery voltage
2. Engine coolant temperature sensor
3. Crankshaft position sensor
4. Intake manifold air temperature sensor
5. Manifold absolute pressure (MAP) sensor
6. Throttle position sensor (TPS)
7. Camshaft position sensor signal

The PCM monitors the crankshaft position sensor. If the PCM does not receive a crankshaft position sensor signal within 3 seconds of cranking the engine, it will shut down the fuel injection system.

The fuel pump is activated by the PCM through the fuel pump relay.

Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then control the injection sequence and injector pulse width by turning the ground circuit to each individual injector on and off.

The PCM determines the proper ignition timing according to input received from the crankshaft position sensor.

ENGINE WARM-UP MODE

This is an Open Loop mode. During engine warm-up, the PCM receives inputs from

1. Battery voltage
2. Crankshaft position sensor
3. Engine coolant temperature sensor
4. Intake manifold air temperature sensor
5. Manifold absolute pressure (MAP) sensor
6. Throttle position sensor (TPS)
7. Camshaft position sensor signal
8. Park/neutral switch (gear indicator signal-auto. trans. only)
9. Air conditioning select signal (if equipped)
10. Air conditioning request signal (if equipped)

Based on these inputs the following occurs

1. Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then control the injection sequence and injector pulse width by turning the ground circuit to each individual injector on and off.
2. The PCM adjusts engine idle speed through the idle air control (IAC) motor and adjusts ignition timing.
3. The PCM operates the A/C compressor clutch through the A/C compressor clutch relay. This is done if A/C has been selected by the vehicle operator and specified pressures are met at the high and low-pressure A/C switches. Refer to «HEATING & AIR CONDITIONING»(/dodge/pickup-r1500/1997-2012/remont/general-servicing-all-makes/#heating-air-conditioning) for additional information.
4. When engine has reached operating temperature, the PCM will begin monitoring O2S sensor input. The system will then leave the warm-up mode and go into closed loop operation.

IDLE MODE

When the engine is at operating temperature, this is a Closed Loop mode. At idle speed, the PCM receives inputs from

1. Air conditioning select signal (if equipped)
2. Air conditioning request signal (if equipped)
3. Battery voltage
4. Crankshaft position sensor
5. Engine coolant temperature sensor
6. Intake manifold air temperature sensor
7. Manifold absolute pressure (MAP) sensor
8. Throttle position sensor (TPS)
9. Camshaft position sensor signal
10. Battery voltage
11. Park/neutral switch (gear indicator signal-auto. trans. only)
12. Oxygen sensors

Based on these inputs, the following occurs

1. Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then control injection sequence and injector pulse width by turning the ground circuit to each individual injector on and off.
2. The PCM monitors the O2S sensor input and adjusts air-fuel ratio by varying injector pulse width. It also adjusts engine idle speed through the idle air control (IAC) motor.
3. The PCM adjusts ignition timing by increasing and decreasing spark advance.
4. The PCM operates the A/C compressor clutch through the A/C compressor clutch relay. This is done if A/C has been selected by the vehicle operator and specified pressures are met at the high and low-pressure A/C switches. Refer to «HEATING & AIR CONDITIONING»(/dodge/pickup-r1500/1997-2012/remont/general-servicing-all-makes/#heating-air-conditioning) for additional information.

CRUISE MODE

When the engine is at operating temperature, this is a Closed Loop mode. At cruising speed, the PCM receives inputs from

1. Air conditioning select signal (if equipped)
2. Air conditioning request signal (if equipped)
3. Battery voltage
4. Engine coolant temperature sensor
5. Crankshaft position sensor
6. Intake manifold air temperature sensor
7. Manifold absolute pressure (MAP) sensor
8. Throttle position sensor (TPS)
9. Camshaft position sensor signal
10. Park/neutral switch (gear indicator signal-auto. trans. only)
11. Oxygen (O2S) sensors

Based on these inputs, the following occurs

1. Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then adjust the injector pulse width by turning the ground circuit to each individual injector on and off.
2. The PCM monitors the O2S sensor input and adjusts air-fuel ratio. It also adjusts engine idle speed through the idle air control (IAC) motor.
3. The PCM adjusts ignition timing by turning the ground path to the coil(s) on and off.
4. The PCM operates the A/C compressor clutch through the clutch relay. This happens if A/C has been selected by the vehicle operator and requested by the A/C thermostat.

ACCELERATION MODE

This is an Open Loop mode. The PCM recognizes an abrupt increase in throttle position or MAP pressure as a demand for increased engine output and vehicle acceleration. The PCM increases injector pulse width in response to increased throttle opening.

DECELERATION MODE

When the engine is at operating temperature, this is an Open Loop mode. During hard deceleration, the PCM receives the following inputs.

1. Air conditioning select signal (if equipped)
2. Air conditioning request signal (if equipped)
3. Battery voltage
4. Engine coolant temperature sensor
5. Crankshaft position sensor
6. Intake manifold air temperature sensor
7. Manifold absolute pressure (MAP) sensor
8. Throttle position sensor (TPS)
9. Camshaft position sensor signal
10. Park/neutral switch (gear indicator signal-auto. trans. only)
11. Vehicle speed

If the vehicle is under hard deceleration with the proper RPM and closed throttle conditions, the PCM will ignore the oxygen sensor input signal. The PCM will enter a fuel cut-off strategy in which it will not supply a ground to the injectors. If a hard deceleration does not exist, the PCM will determine the proper injector pulse width and continue injection.

Based on the above inputs, the PCM will adjust engine idle speed through the idle air control (IAC) motor.

The PCM adjusts ignition timing by turning the ground path to the coil on and off.

WIDE OPEN THROTTLE MODE

This is an Open Loop mode. During wide open throttle operation, the PCM receives the following inputs.

1. Battery voltage
2. Crankshaft position sensor
3. Engine coolant temperature sensor
4. Intake manifold air temperature sensor
5. Manifold absolute pressure (MAP) sensor
6. Throttle position sensor (TPS)
7. Camshaft position sensor signal

During wide open throttle conditions, the following occurs

1. Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then control the injection sequence and injector pulse width by turning the ground circuit to each individual injector on and off. The PCM ignores the oxygen sensor input signal and provides a predetermined amount of additional fuel. This is done by adjusting injector pulse width.
2. The PCM adjusts ignition timing by turning the ground path to the coil(s) on and off.

IGNITION SWITCH OFF MODE

When ignition switch is turned to OFF position, the PCM stops operating the injectors, ignition coil, ASD relay and fuel pump relay.

DESCRIPTION - 5 VOLT SUPPLIES

Two different Powertrain Control Module (PCM) five volt supply circuits are used; primary and secondary.

DESCRIPTION - IGNITION CIRCUIT SENSE

This circuit ties the ignition switch to the Power-train Control Module (PCM).

DESCRIPTION - POWER GROUNDS

The Powertrain Control Module (PCM) has 2 main grounds. Both of these grounds are referred to as power grounds. All of the high-current, noisy, electrical devices are connected to these grounds as well as all of the sensor returns. The sensor return comes into the sensor return circuit, passes through noise suppression, and is then connected to the power ground.

The power ground is used to control ground circuits for the following PCM loads

1. Generator field winding
2. Fuel injectors
3. Ignition coil(s)
4. Certain relays/solenoids
5. Certain sensors

DESCRIPTION - SENSOR RETURN

The Sensor Return circuits are internal to the Powertrain Control Module (PCM).

Sensor Return provides a low-noise ground reference for all engine control system sensors. Refer to POWER GROUNDS for more information.

OPERATION - PCM

The PCM operates the fuel system. The PCM is a pre-programmed, triple microprocessor digital computer. It regulates ignition timing, air-fuel ratio, emission control devices, charging system, certain transmission features, speed control, air conditioning compressor clutch engagement and idle speed. The PCM can adapt its programming to meet changing operating conditions.

The PCM receives input signals from various switches and sensors. Based on these inputs, the PCM regulates various engine and vehicle operations through different system components. These components are referred to as Powertrain Control Module (PCM) Outputs. The sensors and switches that provide inputs to the PCM are considered Powertrain Control Module (PCM) Inputs.

The PCM adjusts ignition timing based upon inputs it receives from sensors that react to: engine RPM, manifold absolute pressure, engine coolant temperature, throttle position, transmission gear selection (automatic transmission), vehicle speed, power steering pump pressure, and the brake switch.

The PCM adjusts idle speed based on inputs it receives from sensors that react to: throttle position, vehicle speed, transmission gear selection, engine coolant temperature and from inputs it receives from the air conditioning clutch switch and brake switch.

Based on inputs that it receives, the PCM adjusts ignition coil dwell. The PCM also adjusts the generator charge rate through control of the generator field and provides speed control operation.

Note. PCM Inputs

1. ABS module (if equipped)
2. A/C request (if equipped with factory A/C)
3. A/C select (if equipped with factory A/C)
4. A/C pressure transducer
5. Auto shutdown (ASD) sense
6. Battery temperature sensor
7. Battery voltage
8. Brake switch
9. J1850 bus (+) circuits
10. J1850 bus (-) circuits
11. Camshaft position sensor signal
12. Crankshaft position sensor
13. Data link connection for DRB scan tool
14. EATX module (if equipped)
15. Engine coolant temperature sensor
16. Fuel level (through J1850 circuitry)
17. Generator (battery voltage) output
18. Ignition circuit sense (ignition switch in on/off/crank/run position)
19. Intake manifold air temperature sensor
20. Knock sensors (2 on 3.7L engine)
21. Leak detection pump (switch) sense (if equipped)
22. Manifold absolute pressure (MAP) sensor
23. Oil pressure
24. Oxygen sensors
25. Park/neutral switch (auto. trans. only)
26. Power ground
27. Power steering pressure switch (if equipped)
28. Sensor return
29. Signal ground
30. Speed control multiplexed single wire input
31. Throttle position sensor
32. Transfer case switch (4WD range position)
33. Vehicle speed signal

Note. PCM Outputs

1. A/C clutch relay
2. Auto shutdown (ASD) relay
3. J1850 bus (+/-) circuits for: speedometer, voltmeter, fuel gauge, oil pressure gauge/lamp, engine temp. gauge and speed control warn, lamp
4. Data link connection for DRB scan tool
5. EGR valve control solenoid (if equipped)
6. EVAP canister purge solenoid
7. Five volt sensor supply (primary)
8. Five volt sensor supply (secondary)
9. Fuel injectors
10. Fuel pump relay
11. Generator field driver (-)
12. Generator field driver (+)
13. Idle air control (IAC) motor
14. Ignition coil(s)
15. Leak detection pump (if equipped)
16. Malfunction indicator lamp (Check engine lamp). Driven through J1850 circuits.
17. Oxygen sensor heater relays
18. Oxygen sensors (pulse width modulated)
19. Radiator cooling fan relay (pulse width modulated)
20. Speed control vacuum solenoid
21. Speed control vent solenoid
22. Tachometer (if equipped). Driven through J1850 circuits.
23. Transmission convertor clutch circuit. Driven through J1850 circuits.

OPERATION - 5 VOLT SUPPLIES

Primary 5-volt supply

1. supplies the required 5 volt power source to the Crankshaft Position (CKP) sensor.
2. supplies the required 5 volt power source to the Camshaft Position (CMP) sensor.
3. supplies a reference voltage for the Manifold Absolute Pressure (MAP) sensor.
4. supplies a reference voltage for the Throttle Position Sensor (TPS) sensor.

Secondary 5-volt supply

1. supplies the required 5 volt power source to the oil pressure sensor.
2. supplies the required 5 volt power source for the Vehicle Speed Sensor (VSS) (if equipped).
3. supplies the 5 volt power source to the transmission pressure sensor (certain automatic transmissions).

OPERATION - IGNITION CIRCUIT SENSE

The ignition circuit sense input tells the PCM the ignition switch has energized the ignition circuit.

Battery voltage is also supplied to the PCM through the ignition switch when the ignition is in the RUN or START position. This is referred to as the "ignition sense" circuit and is used to "wake up" the PCM. Voltage on the ignition input can be as low as 6 volts and the PCM will still function. Voltage is supplied to this circuit to power the PCM's 8-volt regulator and to allow the PCM to perform fuel, ignition and emissions control functions.

The PCM is located in the engine compartment attached to the dash panel (Scheme 5)

To avoid possible voltage spike damage to the PCM, ignition key must be off, and negative battery cable must be disconnected before unplugging PCM connectors.

Scheme 5

1. Disconnect negative battery cable at battery.
2. Remove cover over electrical connectors. Cover snaps onto PCM.
3. Carefully unplug the three 32-way connectors (four 38-way connectors if equipped with NGC) from PCM (Scheme 6)
4. Remove three PCM mounting bolts (Scheme 6) and remove PCM from vehicle.

Scheme 6

1. Install PCM and 3 mounting bolts to vehicle.
2. Tighten bolts.
3. Check pin connectors in the PCM and the three 32-way connectors (four 38-way connectors if equipped with NGC) for corrosion or damage. Also, the pin heights in connectors should all be same. Repair as necessary before installing connectors.
4. Install three 32-way connectors (four 38-way connectors if equipped with NGC).
5. Install cover over electrical connectors. Cover snaps onto PCM.
6. Install negative battery cable.
7. The 5.7L V-8 engine is equipped with a fully electronic accelerator pedal position sensor. If equipped with a 5.7L, also perform the following 3 steps: Connect negative battery cable to battery. Turn ignition switch ON, but do not crank engine. Leave ignition switch ON for a minimum of 10 seconds. This will allow PCM to learn electrical parameters. The DRB III(R) Scan Tool may also be used to learn electrical parameters. Go to the Miscellaneous menu, and then select ETC Learn.
8. If the previous step is not performed, a Diagnostic Trouble Code (DTC) will be set.
9. If necessary, use DRB III(R) Scan Tool to erase any Diagnostic Trouble Codes (DTC's) from PCM. Also use the DRB scan tool to reprogram new PCM with vehicles original Vehicle Identification Number (VIN) and original vehicle mileage.

The Sentry Key Immobilizer Module (SKIM) contains a Radio Frequency (RF) transceiver and a central processing unit, which includes the Sentry Key Immobilizer System (SKIS) program logic. The SKIS programming enables the SKIM to program and retain in memory the codes of at least two, but no more than eight electronically coded Sentry Key transponders. The SKIS programming also enables the SKIM to communicate over the Programmable Communication Interface (PCI) bus network with the Powertrain Control Module (PCM) or Electronic Control Module (ECM), depending on engine application, and/or the DRBIII(R) scan tool.

The SKIM transmits and receives RF signals through a tuned antenna enclosed within a molded plastic ring that is integral to the SKIM housing. When the SKIM is properly installed on the steering column, the antenna ring is oriented around the ignition lock cylinder housing. This antenna ring must be located within eight millimeters (0.31 inches) of the Sentry Key in order to ensure proper RF communication between the SKIM and the Sentry Key transponder.

For added system security, each SKIM is programmed with a unique "Secret Key" code and a security code. The SKIM keeps the "Secret Key" code in memory. The SKIM also sends the "Secret Key" code to each of the programmed Sentry Key transponders. The security code is used by the assembly plant to access the SKIS for initialization, or by the dealer technician to access the system for service. The SKIM also stores in its memory the Vehicle Identification Number (VIN), which it learns through a PCI bus message from the PCM (NGC) or ECM (Cummins) during initialization.

The SKIM and the PCM/ECM both use software that includes a rolling code algorithm strategy, which helps to reduce the possibility of unauthorized SKIS disarming. The rolling code algorithm ensures security by preventing an override of the SKIS through the unauthorized substitution of the SKIM or the PCM/ECM. However, the use of this strategy also means that replacement of either the SKIM or the PCM/ECM units will require a system initialization procedure to restore system operation.

When the ignition switch is turned to the ON or START positions, the SKIM transmits an RF signal to excite the Sentry Key transponder. The SKIM then listens for a return RF signal from the transponder of the Sentry Key that is inserted in the ignition lock cylinder. If the SKIM receives an RF signal with valid "Secret Key" and transponder identification codes, the SKIM sends a "valid key" message to the PCM/ECM over the PCI bus. If the SKIM receives an invalid RF signal or no response, it sends "invalid key" messages to the PCM/ECM. The PCM/ECM will enable or disable engine operation based upon the status of the SKIM messages.

The SKIM also sends messages to the Instrument Cluster which controls the VTSS indicator LED. The SKIM sends messages to the Instrument Cluster to turn the LED on for about three seconds when the ignition switch is turned to the ON position as a bulb test. After completion of the bulb test, the SKIM sends bus messages to keep the LED off for a duration of about one second. Then the SKIM sends messages to turn the LED on or off based upon the results of the SKIS self-tests. If the VTSS indicator LED comes on and stays on after the bulb test, it indicates that the SKIM has detected a system malfunction and/or that the SKIS has become inoperative.

If the SKIM detects an invalid key when the ignition switch is turned to the ON position, it sends messages to flash the VTSS indicator LED. The SKIM can also send messages to flash the LED as an indication to the customer that the SKIS has been placed in it's "Customer Learn" programming mode. See SENTRY KEY IMMOBILIZER SYSTEM TRANSPONDER PRO for more information on the "Customer Learn" programming mode.

For diagnosis or initialization of the SKIM and the PCM/ECM, a DRBIII(R) scan tool and POWERTRAIN DIAGNOSTIC PROCEDURES (PART 1) and POWERTRAIN DIAGNOSTIC PROCEDURES (PART 2) are required. The SKIM cannot be repaired and, if faulty or damaged, the unit must be replaced.

STANDARD PROCEDURE - PCM/SKIM PROGRAMMING

Note. There are two procedures for transfering the secret key to the SKIM: When ONLY the SKIM module is replaced, the secret key is transfered from the PCM (NGC- gasoline engine) or ECM (Cummins - diesel engine) to the SKIM. The ORGINAL KEYS may then be programmed to the SKIM. When ONLY the PCM/ECM is replaced, then the secret key is transfered from the SKIM to the PCM/ECM. The ORGINAL KEYS may be used. When BOTH the SKIM and the PCM/ECM are replaced the secret key is transferred from the SKIM to the PCM/ECM, and NEW KEYS must be programmed.

Note. Before replacing the PCM/ECM (depending on engine application), for a failed driver, control circuit, or ground circuit, be sure to check the related component/circuit integrity for failures not detected due to a double fault in the circuit. Most PCM/ECM driver/control circuit failures are caused by internal component failures (i.e. relay and solenoids) and shorted circuits (i.e. pull-ups, drivers and switched circuits). These failures are difficult to detect when a double fault has occurred and only one Diagnostic Trouble Code (DTC) has set.

When a PCM/ECM and the Sentry Key Immobilizer Module (SKIM) are replaced at the same time perform the following steps in order

1. Program the new PCM/ECM.
2. Program the new SKIM.
3. Replace all ignition keys and program them to the new SKIM.

PROGRAMMING THE PCM (NGC) or ECM (CUMMINS)

The Sentry Key Immobilizer System (SKIS) Secret Key is an ID code that is unique to each SKIM. This code is programmed and stored in the SKIM, PCM/ECM and transponder chip (ignition keys). When replacing the PCM/ECM it is necessary to program the secret key into the new PCM/ECM using the DRBIII(R) scan tool. Perform the following steps to program the secret key into the PCM/ECM.

1. Turn the ignition switch on (transmission in park/neutral).
2. Use the DRBIII(R) scan tool and select THEFT ALARM, SKIM then MISCELLANEOUS.
3. Select PCM REPLACED (GAS ENGINE) or CUMMINS ECM REPLACED (DIESEL ENGINE).
4. Enter secured access mode by entering the vehicle four-digit PIN.
5. Select ENTER to update PCM/ECM VIN. NOTE: If three attempts are made to enter secure access mode using an incorrect PIN, secured access mode will be locked out for one hour. To exit this lockout mode, turn the ignition to the RUN position for one hour then enter the correct PIN. (Ensure all accessories are turned OFF. Also monitor the battery state and connect a battery charger if necessary).
6. Press ENTER to transfer the secret key (the SKIM will send the secret key to the PCM/ECM).
7. Press Page Back to get to the Select System menu and select ENGINE, MISCELLANEOUS, and SRI MEMORY CHECK.
8. On gasoline engine applications (NGC), the DRBIII(R) scan tool will ask, Is odometer reading between XX and XX? Select the YES or NO button on the DRB III(R) scan tool. If NO is selected, the DRBIII(R) scan tool will read, Enter odometer Reading < From I.P. odometer >. Enter the odometer reading from the instrument cluster and press ENTER.

PROGRAMMING THE SKIM

1. Turn the ignition switch on (transmission in park/neutral).
2. Use the DRBIII(R) scan tool and select THEFT ALARM, SKIM then MISCELLANEOUS.
3. Select SKIM REPLACED.
4. Program the vehicle four-digit PIN into SKIM.
5. Select COUNTRY CODE and enter the correct country. NOTE: Be sure to enter the correct country code. If the incorrect country code is programmed into the SKIM, the SKIM must be replaced.
6. Select YES to update the VIN (the SKIM will learn the VIN from the PCM/ECM).
7. Press ENTER to transfer the secret key (the PCM/ECM will send the secret key information to the SKIM).
8. Program ignition keys to the SKIM. NOTE: If the PCM/ECM and the SKIM are replaced at the same time, all vehicle keys will need to be replaced and programmed to the new SKIM.

PROGRAMMING IGNITION KEYS TO THE SKIM

1. Turn the ignition switch on (transmission in park/neutral).
2. Use the DRBIII(R) scan tool and select THEFT ALARM, SKIM then MISCELLANEOUS.
3. Select PROGRAM IGNITION KEY'S.
4. Enter secured access mode by entering the vehicle four-digit PIN. NOTE: A maximum of eight keys can be learned to each SKIM. Once a key is learned to a SKIM, it (the key) cannot be transferred to another vehicle.
5. If ignition key programming is unsuccessful, the DRBIII(R) scan tool will display one of the following messages: Programming Not Attempted - The DRBIII(R) scan tool attempts to read the programmed key status and there are no keys programmed into SKIM memory. Programming Key Failed (Possible Used Key From Wrong Vehicle) - SKIM is unable to program key due to one of the following: Faulty ignition key transponder. Ignition key is programmed to another vehicle. 8 Keys Already Learned, Programming Not Done - SKIM transponder ID memory is full.
6. Obtain ignition keys to be programmed from customer (8 keys maximum).
7. Using the DRBIII(R) scan tool, erase all ignition keys by selecting MISCELLANEOUS and ERASE ALL CURRENT IGN KEYS.
8. Program all ignition keys. Learned Key In Ignition - Ignition key transponder ID is currently programmed in SKIM memory.

Scheme 7

1. Disconnect and isolate the battery negative cable.
2. Remove upper and lower covers (shrouds) from steering column.
3. Disconnect the steering column wire harness connector from the Sentry Key Immobilizer Module (SKIM)
4. Remove the screw that secures the SKIM to the steering column (Scheme 7)
5. Release the SKIM antenna ring retaining clips from around the ignition switch lock cylinder housing and remove the SKIM.

Note. If the SKIM is replaced with a new unit, a DRBIII(R) scan tool MUST be used to initialize the new SKIM and to program at least two Sentry Key transponders before the vehicle can be operated (Refer to VEHICLE THEFT SECURITY ).

1. Position the SKIM antenna ring around the ignition switch lock cylinder housing.
2. Install the SKIM antenna ring retaining clips.
3. Install the screw that secures the SKIM to the steering column.
4. Connect the steering column wire harness connector to the SKIM.
5. Position both the upper and lower shrouds onto the steering column.
6. Install and tighten the screws that secure the lower steering column shroud to the upper shroud. Tighten the screws to 2 N.m (18 in. lbs.).
7. Reconnect the battery negative cable.

The Transfer Case Control Module (TCCM) (Scheme 8) is a microprocessor-based assembly, controlling the 4X4 transfer case shift functions via the actuation of a shift motor and utilizing the feedback of a mode sensor assembly. Communication is via the PCI serial bus. Inputs include user selectable 4X4 modes that include 2WD, AWD, 4HI, 4LO, and Neutral. The logic and driver circuitry is contained in a molded plastic housing with an embedded heat-sink and is located behind the left side of the lower instrument panel.

Scheme 8

The Transfer Case Control Module (TCCM) utilizes the input from the transfer case mounted mode sensor, the instrument panel mounted selector switch, and the following information from the vehicle's PCI serial bus to determine if a shift is allowed.

1. Engine RPM and Vehicle Speed
2. Diagnostic Requests
3. Manual Transmission and Brake Applied
4. PRNDL
5. Ignition Status
6. ABS Messages

Once the TCCM determines that a requested shift is allowed, it actuates the bi-directional shift motor as necessary to achieve the desired transfer case operating mode. The TCCM also monitors the mode sensor while controlling the shift motor to determine the status of the shift attempt.

Several items can cause the requested shift not to be completed. If the TCCM has recognized a fault (DTC) of some variety, it will begin operation in one of four Functionality Levels. These levels are

1. Level Zero - Normal Operation.
2. Level One - Only Mode Shifts Are Allowed.
3. Level Two - Only Mode Shifts and Shifts Into LOW Are Allowed (No Neutral Shifts Are Allowed).
4. Level Three - No Shifts Are Allowed

The TCCM can also be operating in one of three possible power modes. These power modes are

1. Full Power Mode is the normal operational mode of the module. This mode is achieved by normal PCI bus traffic being present and the ignition being in the RUN position.
2. Reduced Power Mode will be entered when the ignition has been powered off. In this state, the module will shut down power supplied to external devices, and to electronic interface inputs and outputs. From this state the module can enter either Sleep Mode or Full Power Mode. To enter this mode, the module must receive an ignition message denoting that the ignition is off, or not receive any messages for 5 +/-0.5 seconds. To exit this mode, the module must receive one ignition message that denotes that the ignition is in the RUN position.
3. Sleep Mode will be entered, from the Reduced Power Mode, when no PCI traffic has been sensed for 20 +/-1 seconds. If during Sleep Mode the module detects PCI bus traffic, it will revert to the Reduced Power mode while monitoring for ignition messages. It will remain in this state as long as there is traffic other than run or start messages, and will return to Sleep mode if the bus goes without traffic for 20 +/-1 seconds.

SHIFT REQUIREMENTS

If the TCCM is in full power mode and at functionality level zero, it uses the following criteria to determine if a shift is allowed.

If any of the driver controllable conditions are not met once the shift request is recognized, the TCCM will solidly illuminate the source position's LED and flash the desired position's LED for all shifts except NEUTRAL. The NEUTRAL shift LED strategy will be discussed later.

Mode shifts will be allowed regardless of transmission gear or vehicle speed, whenever the following conditions are met

1. Front and rear wheel speed are within 21 km/hr (13 mph).
2. A change in the Selector switch state indicates that a mode shift has been requested.
3. A valid mode sensor signal is being sensed by the TCCM.
4. Proper transmit/receive messages are occurring on the PCI bus.
5. Ignition key switch is in the RUN position.

Range shifts will be allowed only if all of the following conditions are met

1. Front and rear wheel speed are within 21 km/hr (13 mph).
2. A change in the Selector Switch state indicating a range shift has been requested.
3. Transmission in NEUTRAL signal must be recognized for at least 1.5 seconds +/-100 msec. (Automatic transmissions only)
4. Proper transmit/receive messages are occurring on the PCI bus.
5. Clutch signal is recognized for 500 msec +/- 50 msec (Manual transmissions only).
6. Vehicle speed is less than or equal to 4.8 km/hr (3 miles per hour).
7. Ignition key switch is in the RUN position.
8. A valid mode sensor signal is being sensed by the TCCM.

A shift into transfer case Neutral will be allowed only if all of the following conditions are met

1. Front and rear wheel speed are within 21 km/hr (13 mph).
2. The recessed Neutral Selection switch has been depressed continuously for 4.0 seconds +/-100 msec while all shift conditions have been continuously met.
3. Transmission in NEUTRAL signal recognized from the bus. (Automatic transmissions only)
4. Clutch signal is recognized from the bus (Manual transmissions only).
5. Proper message transmissions/receptions are occurring on the PCI bus.
6. Vehicle speed is less than or equal to 4.8 km/hr (3 miles per hour).
7. Ignition key switch is in the RUN position, engine off.
8. Foot Brake is applied.
9. A valid mode sensor signal is being sensed by the TCCM.

A shift out of transfer case Neutral will be allowed only if all of the following conditions are met

1. Front and rear wheel speed are within 21 km/hr (13 mph).
2. The recessed Neutral Selection switch has been depressed continuously for 1.0 seconds +/-100 msec while all shift conditions have been continuously met.
3. Transmission in NEUTRAL signal recognized from the bus.(Automatic transmissions only)
4. Clutch signal is recognized from the bus (Manual transmissions only).
5. Proper message transmissions/receptions are occurring on the PCI bus.
6. Vehicle speed is less than or equal to 4.8 km/hr (3 miles per hour).
7. Ignition key switch is in the RUN position.
8. Foot Brake is applied.
9. A valid mode sensor signal is being sensed by the TCCM.

SHIFT SEQUENCES

Once all the driver controllable conditions for the requested shift have been met, the TCCM begins a shift timer with a maximum duration of 1 second per 'D' channel transition. If the shift timer expires before the TCCM recognizes to correct mode sensor code, the shift is considered to have been blocked. The blocked shift will increment the blocked shift counter by one. The TCCM strategy for handling blocked shifts will be described later. The process the TCCM performs for the various shifts will be described first.

RANGE AND MODE SHIFTS

The process for performing all the range and mode shifts are the same. The following steps describe the process.

1. Allow time for Selector Switch debounce; 250 msec +/-50 msec.
2. Extinguish the source gear's LED while flashing desired, transfer case position's LED.
3. Engage the shift motor for a maximum of 1 second +/-100 msec per 'D' channel transition in the destination gear's direction while monitoring the mode sensor channel transitions.
4. Disengage the shift motor when the correct mode sensor code is recognized.
5. Solidly illuminate the selected gear's LED.
6. Transmit a bus message that the transfer case shift is complete.
7. If the desired mode sensor code is not received after the shift timer expires (ie. a blocked or other condition exists), stop driving the motor and wait for 200 msec +/-50 msec. The shift motor is then reversed in the direction back toward the source gear for up to 1.0 seconds +/-100 msec, per 'D' channel. The TCCM waits for 2.0 seconds +/-50 msec. and repeats the attempt to shift to the desired position.

The exception to the preceding sequence is when a shift from 4L to 2WD/AWD is requested. If 2WD/AWD is requested from the 4L position, the transfer case is first driven to the 4H position. If the 4H position is reached, the transfer case is then driven back to the 2WD/AWD position and the shift is considered complete. If the transfer case does not reach any the 4H position, but is in the 2WD/AWD 'D' channel, or the 2WD/AWD between gear position on the 4H side of 2WD/AWD, the shift is also considered complete.

SHIFT OUT OF NEUTRAL

The following steps describe the process for a shift out of NEUTRAL.

1. Extinguish the Neutral LED.
2. Engage the shift motor for a maximum of 1 second +/-100 msec toward the transfer case 4H mode position while monitoring the mode sensor channel transitions.
3. Disengage the shift motor when the correct mode sensor code is recognized.
4. Extinguish the Neutral LED.
5. Transmit a bus message that the transfer case shift is complete.
6. If the desired mode sensor code is not received after the shift timer expires (ie. a blocked or other condition exists), stop driving the motor and wait for 200 msec +/-50 msec. The shift motor is then reversed in the direction back toward the source gear for up to 1.0 seconds 100 msec. The TCCM waits for 2.0 seconds +/-50 msec. and repeats the attempt to shift to the desired position.
7. When the Neutral button is released, if the 4H position is the desired position, the shift is complete. Illuminate the 4H LED.
8. Otherwise when the Neutral button is released, if all of the shift requirements are being met then engage the shift motor towards the desired position for 1 second +/-100 msec per 'D' channel. (if requirements for shifting are not met, illuminate the 4H LED and flash the destination LED as an indication to the driver that all of the driver controllable shift conditions are not being met). If this requires another range or mode shift, begin the range/mode shift process.
9. If the desired mode sensor code is not received after the shift timer expires (i.e. a blocked or other condition exists), refer to «BLOCKED SHIFT STRATEGY»(/dodge/pickup-r1500/1997-2012/remont/body-cab-control-systems/#electronic-control-modules__blocked-shift-strategy) .

BLOCKED SHIFT STRATEGY

When a shift is commanded, the shift motor will be driven towards its destination position, except in the case of shifting out of Neutral if 4L was selected (the transfer case will shift to the 4H position first, before proceeding to 4L). If the shift is blocked on the way to the destination, the TCCM may attempt to drive the motor back to the original position. This process will be allowed to occur 5 times. If the transfer case has reached a non-NEUTRAL 'D' channel during the shift re-attempts, the LED for the achieved gear position is illuminated and the shift attempts are stopped. To re-attempt the desired shift, the selector switch will need to be rotated to the current position until the switch debounce timer expires then a shift will need to be requested again.

At the end of the 5th blocked attempt, the shift motor is driven towards the last known 'D' channel position. If this motor drive allows the transfer case to reach the 2WD/AWD 'D' channel, or the 2WD/AWD between gear position on the 4H side of 2WD/AWD, the shift is considered complete and the shift attempts are ended.

If the mode sensor is in the NEUTRAL region at the expiration of the shift timer, the TCCM will continue to make the shift attempts according to the blocked shift strategy independent of whether or not the driver controlled conditions are met.

For shifts from NEUTRAL, if all 5 attempts fail to reach the desired position (which by default is 4H), the motor will be driven to stall in the direction of 4H or 4L, depending on the achieved position. If the transfer case has reached the 2WD/AWD or 4L between gear position nearest the NEUTRAL positions and the shift conditions are no longer being met, the transfer case will be driven toward the corresponding 'D' channel. Otherwise, the transfer case will be driven in the direction opposite the last attempt with the desired target being 4H or 4L.

If the transfer case reaches the 2WD/AWD 'D' channel when being driven in the 4H direction, then one final 1.0 second drive toward 4H is attempted. If the transfer case then reaches any of the 4H positions, the shift is considered complete and the 4H LED is illuminated. If the transfer case is still the 2WD/AWD position, the shift is considered complete and the 2WD/AWD LED is illuminated.

Note. If after the 5th blocked shift and reversal attempt, if the transfer case position is in the NEUTRAL region, shift attempts will continue until a non-NEUTRAL 'D' channel is reached.

SHIFT REVERSAL TARGETS

If the shift timer expires (1 second per 'D' channel) and the transfer case has not reached the desired position, all shifts will attempt to return to their original position with the exceptions of

1. If the intended shift is going to the High rail from Low and can't make it, but it can make the 2WD/AWD position, the motor stops at that position. The TCCM will not attempt to cross back over NEUTRAL if it does not have to. This means that there was a block on the first attempt to go to 4H and the transfer case has made it through NEUTRAL to a known good position, then the motor will go back only to the 2WD/4WD position and execute the remainder of the attempts from there.
2. For shifts out of NEUTRAL, any time a shift is commanded out of NEUTRAL, the system needs to get out. The TCCM should never go to NEUTRAL unless the driver is commanding it and all required conditions are being met

ENCODER DRIFT CORRECTION

Whenever a shift is completed, the TCCM stores the position in memory as the transfer case's intended position. The TCCM continuously monitors the mode sensor and if the mode sensor drifts toward into a NEUTRAL region sensor position for 2.0 seconds, the TCCM will perform a motor drive to correct the drift. The transfer case will be driven toward the intended position for 1.0 seconds 100 msec. The TCCM will wait for 2.0 seconds +/-50 msec. and repeat the attempt to shift to the desired position. This will continue until the intended position is reached.

SHIFT MOTOR BRAKING

Two modes of shift motor braking are employed to improve shift performance, static and dynamic. Static shift motor braking is utilized under the following conditions

1. Whenever the transfer case is in the 2WD/AWD or 4L 'D' channel position.
2. Whenever an invalid mode sensor code is present. Static motor braking is achieved by applying +12V on both shift motor wires. NOTE: Static Shift Motor Braking is independent of ignition key position.

SHIFT ATTEMPT LIMIT

To protect the transfer case system, the TCCM will impose a limit on the number of shifts that can occur over a calibrated time period. The system will monitor the number of 'D' channel segment transitions that occur in any 30 second time period. If the number of segment transitions is 30 or greater, the system will go into a default mode. The default mode of operation for shifting is that the number of allowed 'D' channel transitions permitted to occur will be 3 over each 15 second +/-100 msec calibrated window of time. After 5 minutes +/-100 msec, the motor can be assumed to have cooled down and the system will revert to normal operation. The following rules also apply to the shift limit

1. The attempt limit will not prevent shifts coming out of NEUTRAL, they will be allowed regardless of the counter/timer.
2. Any shift that is in progress when the counter reaches a maximum count in time will be allowed to complete before the default mode is entered. D-channel transitions during this period will not be counted towards the default mode limit.
3. A block, regardless of the direction, whether towards destination or back towards reversal target (shift timer expiring), will count as a value of 2 transitions towards the 30 segment transitions to go into default mode as defined above. Current attempt limit values are 30 transitions in 30 seconds and default mode values are 3 transitions every 15 seconds for 5 minutes.

The Transmission Control Module (TCM) (Scheme 9) may be sub-module within the Powertrain Control Module (PCM), Engine Control Module (ECM - Diesel only) (Scheme 10), or a standalone module, depending on the vehicle engine. The PCM, and TCM when equipped, is located at the right rear of the engine compartment, near the right inner fender.

Scheme 9

Scheme 10

The Transmission Control Module (TCM) controls all electronic operations of the transmission. The TCM receives information regarding vehicle operation from both direct and indirect inputs, and selects the operational mode of the transmission. Direct inputs are hardwired to, and used specifically by the TCM. Indirect inputs are shared with the TCM via the vehicle communication bus.

Some examples of direct inputs to the TCM are

1. Battery (B+) voltage
2. Ignition "ON" voltage
3. Transmission Control Relay (Switched B+)
4. Throttle Position Sensor
5. Crankshaft Position Sensor
6. Transmission Range Sensor
7. Pressure Switches
8. Transmission Temperature Sensor
9. Input Shaft Speed Sensor
10. Output Shaft Speed Sensor
11. Line Pressure Sensor

Some examples of indirect inputs to the TCM are

1. Engine/Body Identification
2. Manifold Pressure
3. Target Idle
4. Torque Reduction Confirmation
5. Engine Coolant Temperature
6. Ambient/Battery Temperature
7. DRBIII(R) Scan Tool Communication

Based on the information received from these various inputs, the TCM determines the appropriate shift schedule and shift points, depending on the present operating conditions and driver demand. This is possible through the control of various direct and indirect outputs.

Some examples of TCM direct outputs are

1. Transmission Control Relay
2. Solenoids
3. Torque Reduction Request

Some examples of TCM indirect outputs are

1. Transmission Temperature (to PCM)
2. PRNDL Position (to BCM)

In addition to monitoring inputs and controlling outputs, the TCM has other important responsibilities and functions

1. Storing and maintaining Clutch Volume Indexes (CVI)
2. Storing and selecting appropriate Shift Schedules
3. System self-diagnostics
4. Diagnostic capabilities (with DRBIII(R) scan tool)

Note. If the TCM has been replaced, the "Quick Learn Procedure" must be performed. (Refer to STANDARD PROCEDURE )

BATTERY FEED

A fused, direct battery feed to the TCM is used for continuous power. This battery voltage is necessary to retain memory in the TCM. When the battery (B+) is disconnected, this memory is lost. When the battery (B+) is restored, this memory loss is detected by the TCM and a Diagnostic Trouble Code (DTC) is set.

CLUTCH VOLUME INDEXES (CVI)

An important function of the TCM is to monitor Clutch Volume Indexes (CVI). CVIs represent the volume of fluid needed to compress a clutch pack.

The TCM monitors gear ratio changes by monitoring the Input and Output Speed Sensors. The Input, or Turbine Speed Sensor sends an electrical signal to the TCM that represents input shaft RPM. The Output Speed Sensor provides the TCM with output shaft speed information.

By comparing the two inputs, the TCM can determine transmission gear position. This is important to the CVI calculation because the TCM determines CVIs by monitoring how long it takes for a gear change to occur (Scheme 11)

Scheme 11

Gear ratios can be determined by using the DRBIII(R) Scan Tool and reading the Input/Output Speed Sensor values in the "Monitors" display. Gear ratio can be obtained by dividing the Input Speed Sensor value by the Output Speed Sensor value.

For example, if the input shaft is rotating at 1000 RPM and the output shaft is rotating at 500 RPM, then the TCM can determine that the gear ratio is 2:1. In direct drive (3rd gear), the gear ratio changes to 1:1. The gear ratio changes as clutches are applied and released. By monitoring the length of time it takes for the gear ratio to change following a shift request, the TCM can determine the volume of fluid used to apply or release a friction element.

The volume of transmission fluid needed to apply the friction elements are continuously updated for adaptive controls. As friction material wears, the volume of fluid need to apply the element increases.

Certain mechanical problems within the input clutch assembly can cause inadequate or out-of-range element volumes. Also, defective Input/Output Speed Sensors and wiring can cause these conditions. The following chart identifies the appropriate clutch volumes and when they are monitored/updated

CLUTCH VOLUMES

SHIFT SCHEDULES

As mentioned earlier, the TCM has programming that allows it to select a variety of shift schedules. Shift schedule selection is dependent on the following

1. Shift lever position
2. Throttle position
3. Engine load
4. Fluid temperature
5. Software level

As driving conditions change, the TCM appropriately adjusts the shift schedule. Refer to SHIFT SCHEDULES CHART to determine the appropriate operation expected, depending on driving conditions.

SHIFT SCHEDULES CHART

STANDARD PROCEDURE - TCM QUICK LEARN

The quick learn procedure requires the use of the DRB(R) scan tool.

This program allows the electronic transmission system to recalibrate itself. This will provide the proper transmission operation. The quick learn procedure should be performed if any of the following procedures are performed

1. Transmission Assembly Replacement
2. Transmission Control Module Replacement
3. Solenoid Pack Replacement
4. Clutch Plate and/or Seal Replacement
5. Valve Body Replacement or Recondition

To perform the Quick Learn Procedure, the following conditions must be met

1. The brakes must be applied
2. The engine speed must be above 500 RPM
3. The throttle angle (TPS) must be less than 3 degrees
4. The shift lever position must stay in PARK until prompted to shift to overdrive
5. The shift lever position must stay in overdrive after the Shift to Overdrive prompt until the DRB(R) indicates the procedure is complete
6. The calculated oil temperature must be above 60° and below 200°

STANDARD PROCEDURE - DRIVE LEARN

When a transmission is repaired and a Quick Learn procedure has been performed on the Transmission Control Module (TCM), the following Drive Learn procedure can be performed to fine tune any shifts which are particularly objectionable.

Note. It is not necessary to perform the complete Drive Learn procedure every time the TCM is Quick Learned. Perform only the portions which target the objectionable shift.

LEARN A SMOOTH 1ST NEUTRAL TO DRIVE SHIFT

Perform this procedure only if the complaint is for a delayed or harsh shift the first time the transmission is put into gear after the vehicle is allowed to set with the engine not running for at least 10 minutes. Use the following steps to have the TCM learn the 1st N-D UD CVI.

Note. The transmission oil temperature must be between 80 - 110°F (27 - 43°C).

1. Start the engine only when the engine and ignition have been off for at least ten (10) minutes.
2. With the vehicle at a stop and the service brake applied, record the 1st N-D UD CVI while performing a Neutral to Drive shift. The 1st N-D UD CVI accounts for air entrapment in the UD clutch that may occur after the engine has been off for a period of time.
3. Repeat Step 1 and Step 2 until the recorded 1st N-D UD CVI value stabilizes. NOTE: It is important that this procedure be performed when the transmission temperature is between 80 - 110°F (27 - 43°C). If this procedure takes too long to complete fully for the allowed transmission oil temperature, the vehicle may be returned to the customer with an explanation that the shift will improve daily during normal vehicle usage. The TCM also learns at higher oil temperatures, but these values (line pressure correction values) are not available for viewing on the DRB(R) III.

LEARN A SMOOTH NEUTRAL TO DRIVE GARAGE SHIFT

Perform this procedure if the complaint is for a delayed or harsh shift when the transmission is put into gear after the vehicle has had its first shift. Use the following steps to have the TCM learn the Norm N-D UD CVI.

Note. The transmission oil temperature must be between 80 - 110°F (27 - 43°C) to learn the UD CVI. Additional learning occurs at temperatures as low as 0°F and as high as 200°F. This procedure may be performed at any temperature that experiences poor shift quality. Although the UD CVI may not change, shift quality should improve.

1. Start the vehicle engine and shift to drive.
2. Move the vehicle forward to a speed of at least 16 km/h (10 MPH) and come to a stop. This ensures no air is present in the UD hydraulic circuit.
3. Perform repeated N-D shifts at a stop while pausing in Neutral for at least 2-3 seconds and monitor Norm N-D UD CVI volume until the value stabilizes. The value will change during the N-D shift. This is normal since the UD value is different for the N-D shift then the normal value shown which is used for 4-3 coastdown and kickdowns. Perform repeated shifts in this temperature range until the Norm N-D UD CVI value stabilizes and the N-D shifts become smooth.

LEARN THE 1ST 2-3 SHIFT AFTER A RESTART OR SHIFT TO REVERSE

Use the following steps to have the TCM learn the 1st 2-3 shift OD CVI.

Note. The transmission oil temperature must be above 80°F (27°C).

1. With the vehicle engine running, select reverse gear for over 2 seconds.
2. Shift the transmission to Drive and accelerate the vehicle from a stop at a steady 15 degree throttle opening and perform a 2-3 shift while noting the 1st 2-3 OD CVI.
3. Repeat Step 1 and Step 2 until the 1st 2-3 upshift becomes smooth and the 1st 2-3 OD CVI stabilizes.

LEARN A SMOOTH 2-3 AND 3-4 UPSHIFT

Note. The transmission oil temperature must be above 110°F (43°C).

Use the following steps to have the TCM learn the OD and 4C CVI's.

1. Accelerate the vehicle from a stop at a steady 15 degree throttle opening and perform multiple 1-2, 2-3, and 3-4 upshifts. The 2nd 2-3 shift following a restart or shift to reverse will be shown during the shift as a value between the 1st 2-3 OD CVI and the normal OD CVI. Updates to the normal OD CVI will occur after the 2nd shift into 3rd gear, following a restart or shift to reverse.
2. Repeat Step 1 until the 2-3 and 3-4 shifts become smooth and the OD and 4C CVI become stable.

LEARN A SMOOTH 4-3 COASTDOWN AND PART THROTTLE 4-3 KICKDOWN

Note. The transmission oil temperature must be above 110°F (43°C).

Use the following steps to have the TCM learn the UD shift volume.

1. At a vehicle speed between 64-97 km/h (40-60 MPH), perform repeated 4-3 kickdown shifts.
2. Repeat Step 1 until the UD volume becomes somewhat stable and the shift becomes smooth.

LEARN A SMOOTH 1-2 UPSHIFT AND 3-2 KICKDOWN

Use the following steps to have the TCM learn the 2C shift volume.

Note. The transmission oil temperature must be above 110°F (43°C).

1. With a vehicle speed below 48 km/h (30 MPH) and the transmission in 3rd gear, perform multiple 3-2 kickdowns.
2. Repeat Step 1 until the 3-2 kickdowns become smooth and the 2C CVI becomes stable.

LEARN A SMOOTH MANUAL 2-1 PULLDOWN SHIFT AS WELL AS A NEUTRAL TO REVERSE SHIFT

Note. The transmission oil temperature must be above 110°F (43°C).

Use the following steps to have the TCM learn the LR volume.

1. With the vehicle speed around 40-48 km/h (25-30 MPH) in Manual 2nd, perform manual pulldowns to Low or 1st gear at closed throttle.
2. Repeat Step 1 until the LR CVI becomes stable and the manual 2-1 becomes smooth.

LEARN A SMOOTH NEUTRAL TO REVERSE SHIFT

Note. The transmission oil temperature must be above 110°F (43°C).

1. With the vehicle at a stop, perform Neutral to Reverse shifts until the shift is smooth. An unlearned Neutral to Reverse shift may be harsh or exhibit a double bump.
2. If any of the shifts are still not smooth after the clutch volume stabilizes, an internal transmission problem may be present.

LEARN A SMOOTH 4-5 UPSHIFT

Note. The transmission oil temperature must be above 110°F (43°C).

Use the following steps to have the TCM learn the Alt 2C CVI.

1. Accelerate the vehicle through 88 km/h (55mph) at a steady 10-15 degree throttle opening and perform multiple 4-5 upshifts.
2. Repeat Step 1 until the 4-5 shift become smooth and theAlt 2C CVI become stable. There is a separate 2C volume used and learned for 4-5 shifts, 2CA. It is independent of the 2C CVI learned on 3-2 kickdowns.

See also:
• INTEGRATED POWER MODULE
• HEATED SEAT SYSTEM
• HEATING & AIR CONDITIONING
• SENTRY KEY IMMOBILIZER SYSTEM TRANSPONDER PRO
• POWERTRAIN DIAGNOSTIC PROCEDURES (PART 1)
• POWERTRAIN DIAGNOSTIC PROCEDURES (PART 2)
• VEHICLE THEFT SECURITY
• REMOVAL
• POWER GROUNDS
• BLOCKED SHIFT STRATEGY