Electronic Control Modules - Service Information: Overview Dodge Durango II

DESCRIPTION

The Antilock Brake Module (ABM) is a microprocessor which handles testing, monitoring and controlling the ABS brake system operation.

The ABM is mounted on the top of the hydraulic control unit (HCU). The ABM operates the ABS system and is separate from other vehicle electrical circuits. ABM voltage source is through CKT A111 (fused B+).

Note. If the ABM needs to be replaced, the rear axle type and tire revolutions per mile must be programed into the new ABM. For axle type refer to REAR AXLE - 8 1/4 or REAR AXLE - 9 1/4 . For tire revolutions per mile, (Refer to TIRES/WHEELS ). To program the ABM refer to the appropriate Diagnostic Service Information. Refer to P1078-TIRE EVOLUTIONS RANGE PERFORMANCE and P1079-TONE WHEEL TEETH COUNT RANGE PERFORMANCE .

The Controller Area Network (CAN) is a serial data bus communication network used for interconnecting numerous electronic control modules throughout the vehicle in a two-wire multiplexed system. Within this context the term serial refers to electronic data that is transferred bit by bit, while bus refers to the shared wires through which that data is transferred. Multiplexing is any system that enables the transmission of multiple messages over a single channel or circuit. The communication protocol being used is a non-proprietary, open standard adopted from the Bosch CAN Specification 2.0b and uses an 11-bit message identifier.

There are actually three separate CAN bus systems used in the vehicle. They are designated: the CAN-B, the CAN-C and the Diagnostic CAN-C. The CAN-B and CAN-C systems provide on-board communication between all nodes in the vehicle. The CAN-C is the faster of the two systems providing near real-time communication (500 Kbps), but is less fault tolerant than the CAN-B system. The CAN-C is used exclusively for communications between critical powertrain and chassis nodes. The slower (83.3 Kbps), but more fault tolerant CAN-B system is used for communications between body and interior nodes. The CAN-B fault tolerance comes from its ability to revert to a single wire communication mode if there is a fault in the bus wiring.

The Diagnostic CAN-C bus is also capable of 500 Kbps communication, and is sometimes informally referred to as the CAN-D system to differentiate it from the other high speed CAN-C bus. A central gateway or hub integral to the Front Control Module (FCM) physically and electrically isolates the three CAN buses from each other and coordinates the bi-directional transfer of messages between the three buses. The FCM is located on the Integrated Power Module (IPM), which is located in the engine compartment near the battery. The Diagnostic CAN-C is used exclusively for the transmission of diagnostic information between the FCM/gateway and a diagnostic scan tool connected to the industry-standard 16-way Data Link Connector (DLC) located beneath the instrument panel on the driver side of the vehicle.

Each node is connected in parallel to its CAN-B or CAN-C bus using a two-wire twisted pair. These wires are wrapped around each other to provide shielding from unwanted electromagnetic induction interfering with the relatively low voltage signals being carried through them. The twisted pairs have between 33 and 50 twists per meter. While the CAN bus is operating, one of the bus wires will carry a higher voltage and is referred to as the CAN High or CAN bus (+) wire, while the other bus wire will carry a lower voltage and is referred to as the CAN Low or CAN bus (-) wire. Each twisted pair terminates at the FCM/gateway.

The added speed of the CAN data bus is many times faster than previous data bus systems. This added speed facilitates the addition of more electronic control modules or nodes and the incorporation of many new electrical and electronic features in the vehicle. Like prior data bus systems, the CAN data bus minimizes redundant wiring connections and, at the same time, reduces wire harness complexity, sensor current loads and controller hardware by allowing each sensing device to be connected to only one node. Each node reads, then broadcasts its sensor data over the bus for use by all other nodes requiring that data.

OPERATION

The Controller Area Network (CAN) data bus allows all electronic modules or nodes connected to the bus to share information with each other. Each node can both send and receive serial data simultaneously. The CAN bus signal lines have termination through a termination resistor within each node, either dominant or recessive. The serial data is made up of high and low voltage pulses strung together. Each string of voltage pulses forms a message.

Regardless of whether a message originates from a node on the medium speed CAN-B bus or on the high speed CAN-C bus, the message structure and layout is the same, which allows the Front Control Module (FCM)/Central GateWay (sometimes referred to as the FCMCGW) to process and transfer messages between the buses. The priority of each message is based upon the 11-bit message identifier. Each node uses arbitration to sort the message priority if two competing messages are attempting to be broadcast at the same time.

The FCM used in the CAN system has more control than a non-CAN FCM. Available options are configured into the FCM at the assembly plant, but additional options can be added in the field using the diagnostic scan tool. The configuration settings are stored in non-volatile memory. The FCM also has two 64-bit registers, which register each of the "as-built" and "currently responding" nodes on the CAN-B and CAN-C buses. The FCM stores a Diagnostic Trouble Code (DTC) in one of two caches for any detected active or stored faults in the order in which they occur. One cache stores powertrain (P-Code), chassis (C-Code) and body (B-Code) DTCs, while the second cache is dedicated to storing network (U-Code) DTCs.

If there are intermittent or active faults in the CAN network, a diagnostic scan tool connected to the Diagnostic CAN-C bus through the 16-way Data Link Connector (DLC) may only be able to communicate with the FCM. To aid in CAN network diagnosis, the FCM will provide CAN-B and CAN-C network status information to the scan tool using certain diagnostic signals. In addition, the transceiver in each node on the CAN-C bus will identify a "bus off hardware failure," while the transceiver in each node on the CAN-B bus will identify a "general bus hardware failure." The transceivers for some CAN-B nodes will also identify "bus shorted high," "bus shorted low," "bus open" or "bus shorted together" failures for both CAN-B bus signal wires.

In order to minimize the potential effects of Ignition-Off Draw (IOD), the CAN-B network employs a sleep strategy. However, a network sleep strategy should not be confused with the sleep strategy of the individual nodes on that network, as they may differ. For example: The CAN-C bus network is awake only when the ignition switch is in the On or Start positions; however, the FCM or the Transmission Control Module (TCM), which are on the CAN-C bus, may still be awake with the' ignition switch in the Accessory or Unlock positions. The integrated circuitry of an individual node may be capable of processing certain sensor inputs and outputs without the need to utilize network resources.

The CAN-B bus network remains active until all nodes on that network are ready for sleep. This is determined by the network using tokens in a manner similar to polling. When the last node that is active on the network is ready for sleep, and it has already received a token indicating that all other nodes on the bus are ready for sleep, ' broadcasts a "bus sleep acknowledgment" message that causes the network to sleep. Once the CAN-B bus network is asleep, any node on the bus can awaken it by transmitting a message on the network. The FCM will keep either the CAN-B or the CAN-C bus awake for a timed interval after it receives a diagnostic message for that bus over the Diagnostic CAN-C bus.

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

The Data Link Connector (DLC) is an industry-standard 16-way connector that permits the connection of a diagnostic scan tool to the Controller Area Network (CAN) for interfacing with, configuring, and retrieving Diagnostic Trouble Code (DTC) data from the electronic modules that reside on the data bus network of the vehicle.

The Front Control Module (FCM) is a micro controller based module located in the left front corner of the engine compartment. The front control module mates to the power distribution center to form the Integrated Power Module (IPM). The IPM 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 tired switch inputs and data received on the CAN bus circuit.

Scheme 1

As messages are sent over the CAN bus circuit, the Front Control Module (FCM) 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 FCM

1. Front turn signals
2. Stop, turn signal and tail lamps
3. Front and rear hazard warning lamps
4. Headlamps
5. Fog Lamps
6. Daytime running lamps - if equipped
7. Horn
8. Windshield and liftgate wiper and washer systems
9. Transfer case shifting
10. Trailer tow wiring output
11. Rear window defroster power and timing
12. Air conditioning condenser cooling fan

The FCM provides the following features for the above function

1. It provides a illuminated approach feature that turns the headlamps on when the vehicle is unlocked with the Remote Keyless Entry (RKE) transmitter.
2. It flashes lamps in response to turn signal, RKE and Vehicle Theft Security System (VTSS) inputs.
3. It sounds the horn in response to RKE and VTSS inputs.
4. It turns off the horn in the event of excessively long operation that could otherwise damage the horn.
5. It turns off the windshield washer motor after 10 seconds of continuous operation to protect the motor.
6. It minimizes voltage variations to the headlamps to extend bulb life and to equalize the light output from the lamps, which might otherwise differ due to variations in wiring resistance.
7. If the headlamps are left on, it automatically turns them off after eight minutes to protect the battery from discharge. It monitors battery voltage and turns off non-essential functions such as the fog lamps, rear window defogger, and heated seats if necessary to conserve battery power.
8. It operates the high-beam headlamps at reduced intensity by pulse-width modulation of the power supply to provide the daytime running lamps.
9. It provides the variable delay intermittent windshield and liftgate wiper time delay features, and the vehicle speed sensitive windshield wiper delay variation.
10. It acts as a link between the CAN bus network for critical powertrain and anti-lock brake systems and the network for body and interior modules.

Scheme 2

1. Disconnect the positive and negative battery cables from the battery.
2. Partially remove the Integrated Power Module (IPM) from the engine compartment.
3. Remove the front control module retaining screws.
4. Pull the front control module straight from the IPM.

Scheme 3

1. Press the Front Control Module (FCM) onto the Integrated Power Module (IPM).
2. Install the mounting fasteners.
3. Install the IPM.
4. Connect the positive and negative battery cables.

There are two Memory Mirror Modules (these are sometimes referred to as Driver Door Modules (DDM) and Passenger Door Modules (PDM) within the memory system. One located in the driver door and one in the passenger door, just behind the door trim panel. The modules send a bus message to the power mirrors to adjust them to a preset position when a memory recall request has been made.

The memory mirror modules also act as an interface in each door for electrical functions (door lock switches and door ajar switches).

The Memory System makes available for immediate recall personalized preferences of the following

Scheme 4

1. Automatic temperature control settings.
2. Outside mirror positions.
3. Power adjustable brake and accelerator pedal position.
4. Power seat horizontal, vertical, recliner, and easy entry positions.
5. Radio push button station selections.

The major components, of the Memory System are

1. Memory Selector Switch - located in the driver door trim panel.
2. Driver Memory Mirror Module (DMMM) - located in the driver door, behind the trim panel.
3. Passenger Memory Mirror Module (PMMM) - located in the passenger door, behind the trim panel.
4. Sentry Key Remote Entry Module (SKREEM) - located at ignition key cylinder.
5. Remote Keyless Entry (RKE) Transmitter - located with ignition key.
6. Memory Seat Module (MSM) - located underneath the driver seat and also controls the Adjustable Pedals.
7. Radio - located in the instrument panel center stack.
8. Automatic Temperature Control (ATC) - located in the instrument panel center stack.

The memory recall is available at the press of a button on the drivers door trim panel or, by using the Remote Keyless Entry (RKE) transmitter if it is programmed to trigger the recall.

Radio settings include up to 20 push button presets (10 AM and 10 FM), and the last station selection, even if it is not one of the 20 preset selections.

The memory mirror module receives input from the door lock switches and sends that message to the cluster for door lock operation (vehicles equipped with memory system only). It also controls the mirror adjustment by receiving input from the mirror switch on the door trim panel. Sensors in the mirrors act as inputs to the memory mirror module in order to position the mirrors to presets by the driver(s). The power supply to the mirrors is supplied by the mirror memory modules. On vehicles equipped with a memory system, the front door ajar switches are inputs to the memory mirror module. The modules use this information for door lock inhibit etc.

A memory setting is saved by pressing the "set" button, then pressing either the memory "1" or "2" button within 5 seconds of pressing the "set" button.

A memory setting is recalled by pressing either the memory "1" or "2" button, or by pressing the unlock button on a "linked" Remote Keyless Entry (RKE) transmitter.

For driver safety, memorized settings can not be recalled if the transmission is in a position other than Park or the seat belt is latched.

Both driver and passenger modules provide active and stored Diagnostic Trouble Codes (DTC's) to aid in diagnosis.

Both modules are identical in appearance with the exception of an extra ground wire on the driver side memory mirror module.

The Memory Seat Module (MSM) is located underneath the driver seat, towards the front and on the outboard side. It is used in conjunction with the other modules in the memory system (Refer to MODULE-MEMORY MIRROR to recall the seat to one of two preset seat functional adjustments (horizontal, vertical, and recliner)). The switch for the memory seat programming and selection mounts on the driver door trim panel. The MSM also controls the adjustable pedals, both for the memory and manual functionality. The adjustable accelerator and brake pedals are available on SLT and Limited models. On Limited, their positioning can be stored for recall by the memory system, allowing for two drivers to have unique, pre-programmed settings.

Scheme 5

The PCM (2) is attached to the right-front inner fender (1) located in the engine compartment.

Scheme 6

DESCRIPTION - MODES OF OPERATION

As input signals to the Powertrain Control Module (PCM) change, the PCM adjusts its response to the output devices.

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.

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 Powertrain Control Module (PCM). Battery voltage is 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.

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.

DESCRIPTION - SIGNAL GROUND

Signal ground provides a low noise ground to the data link connector.

The PCM is a pre-programmed, 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 regulate? various engine and vehicle operations through different system components. These components are referred to a 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 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: Accelerator pedal position sensor (if equipped) A/C request (if equipped with factory A/C) A/C select (if equipped with factory A/C) Auto shutdown (ASD) sense Battery temperature Battery voltage Brake switch CAN bus (+) circuits CAN bus (-) circuits Camshaft position sensor signal Clutch Interlock Switch (if equipped) Crankshaft position sensor Data link connection for diagnostic scan tool EGR position sensor (if equipped) Engine coolant temperature sensor Fuel level Generator (battery voltage) output Ignition circuit sense (ignition switch in on/off/crank/run position) Intake manifold air temperature sensor Knock sensor(s) (if equipped) Leak detection pump (switch) sense (if equipped) Manifold absolute pressure (MAP) sensor Oil pressure sensor Output shaft speed sensor Overdrive/override switch Oxygen sensors Park/neutral switch (auto, trans. only) Power ground Power steering pressure switch (if equipped) Sensor return Signal ground Speed control multiplexed single wire input Throttle position sensor Transmission governor pressure sensor Transmission output speed sensor Transmission temperature sensor Vehicle speed inputs from ABS or RWAL system

Note. PCM Outputs: A/C clutch relay Auto shutdown (ASD) relay CAN bus (+/-) circuits for: speedometer, voltmeter, fuel gauge, oil pressure gauge/lamp, engine temp, gauge and speed control warn. lamp Data link connection for diagnostic scan tool Double start override (if equipped) EGR valve control solenoid (if equipped) Electronic throttle control EVAP canister purge solenoid Five volt sensor supply (primary) Five volt sensor supply (secondary) Fuel injectors Fuel pump relay Generator field driver (-) Generator field driver (+) Generator lamp (if equipped) Idle air control (IAC) motor Ignition coil(s) CAN bus circuits Leak detection pump (if equipped) Malfunction indicator lamp (Check engine lamp). Driven through CAN bus circuits. Overdrive indicator lamp (if equipped) Radiator cooling fan (if equipped) Speed control vacuum solenoid Speed control vent solenoid Starter relay Tachometer (if equipped). Driven through CAN bus circuits. Transmission convertor clutch circuit Transmission 3-4 shift solenoid Transmission relay Transmission temperature lamp (if equipped) Transmission variable force solenoid

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 (if equipped with an RE automatic transmission).

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 Front Control Module (FCM) now contains the software to control the electric shift transfer cases in this vehicle. A separate Transfer Case Control Module (TCCM) is not used. The FCM 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 CAN bus. Inputs include user selectable 4X4 modes that include AWD, 4LOCK, 4LO, and Neutral.

(Refer to MODULE-FRONT CONTROL ) for additional information.

Scheme 7

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

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

Once the FCM 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 FCM 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 FCM 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 FCM 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 CAN 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 CAN traffic has been sensed for 20 +/-1 seconds. If during Sleep Mode the module detects CAN 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.

The Transmission Control Module (TCM) is a sub-module within the Powertrain Control Module (PCM). The PCM is located on the right inner fender.

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 hard wired 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

Scheme 8

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. 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 cluster/CCN)

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 scan tool)

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