Electronic Control Modules - Service Information: Overview Dodge Magnum I

OPERATION

The primary functions of the Antilock Brake Module (ABM) are to

1. Monitor the Antilock Brake System (ABS) and Electronic Stability Program (ESP) for proper operation.
2. Detect wheel locking or wheel slipping tendencies by monitoring the speed of all four wheels of the vehicle.
3. Control fluid modulation to the wheel brakes while the system is in ABS or traction control mode.
4. Modulates fluid pressure to the wheel brakes to control vehicle yaw rate in ESP mode.
5. Store diagnostic information.
6. Provide communication to the scan tool while in diagnostic mode.
7. Illuminate the amber TCS/ESP indicator in the instrument cluster.

The ABM constantly monitors the ABS and ESP (if equipped) for proper operation. If the ABM detects a fault, it will turn on the amber TCS/ESP indicator and disable the ABS or ESP if so equipped. The normal base braking system will remain operational at that time.

The ABM continuously monitors the speed of each wheel through the signals generated by the wheel speed sensors to determine if any wheel is beginning to lock. When a wheel locking tendency is detected, the ABM commands the ABM solenoid coils to actuate. The coils then open and close the valves in the HCU that modulate brake fluid pressure in some or all of the hydraulic circuits. The ABM continues to control pressure in individual hydraulic circuits until a locking tendency is no longer present.

Scheme 1

Scheme 2

Scheme 3

Scheme 4

Scheme 5

1. Disconnect negative (-) battery cable (2) from battery post and isolate.
2. Disconnect 47-Way wiring connector (4) at ABM (6).
3. Unclip brake tubes (1, 2 and 10) from two routing clips (6) along upper radiator support.
4. Unclip brake tube (3) from routing clip (4) below Fuse And Relay Center.
5. Lift up on entire assembly (5) from mounting grommets (8) and move inboard allowing access to ABM attaching screws. Do not force brake tubes. Move assembly just enough to access mounting screws.
6. Remove three screws (2) attaching ABM (1).
7. Slide ABM (1) off HCU (3).

DESCRIPTION

All models use the Controller Area Network (CAN) protocol for their intra-vehicle communications networks (data buses).

Compared to its predecessor, J1850, CAN architecture offers the following improvements

1. Eight times faster to ensure that messages reach their destinations in a timely manner (J1850 operates at 10.4 Kbs compared to 83.3 Kbs for the CAN system).
2. Built-in error checking capabilities for increased reliability.

This model uses four buses: CAN B, CAN C, diagnostic CAN C and the LIN (Local Interconnect Network) data bus. CAN B and the LIN bus operate at a lower speed than CAN C and diagnostic CAN C to provide communication among body and interior modules. CAN C is exclusively for critical powertrain, anti-lock brake and electronic stability program functions. The LIN bus is used on a limited basis for the steering wheel switches that control the EVIC. LIN is used for a local area where wires need to be kept to a minimum. The LIN used on this model is a single wire that takes information and places it on the CAN B bus. The diagnostic CAN C bus transmits diagnostic information to an industry-standard connector for access by service personnel using a plug-in scan tool. This system allows diagnostic data to be obtained from the other two bus systems without affecting the functions of either.

The added communication speed specifically allows the All-Speed Traction Control and ESP (Electronic Stability Program) modules to notify the powertrain control module when engine torque change or a transmission shift are required to avoid wheel slip and maintain stability. Data from control modules on the CAN-C network elsewhere in the vehicle, such as vehicle speed, is transmitted to the body and interior CAN-B network via an interface in the IPM (Intelligent Power Module).

Scheme 6

The door modules control the express up and down feature as well as normal window functions. It is used only on vehicles equipped with the express up feature. If equipped with memory system, the door module controls the memory mirror. The modules are attached to each front door trim panel.

If the vehicle is equipped with the Express Up power window feature there will be a door module on each front door trim panel. The power window switches and motors are directly wired to the modules. If the vehicle is equipped with the Memory System, the exterior power mirrors and switches are also directly wired to the modules along with the rear door window switches. The modules are wired to the accessory delay relay which allows the operation of the windows and mirrors for a given period of time after the ignition is turned off and providing the doors are not opened. The modules communicate with each other and other modules on the vehicle via the CAN-B bus circuit. There are several Diagnostic Trouble Codes (DTC's) the modules will store if there are problems with the power window system or the memory power mirror system.

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

The FCM provides the following features for the above function

1. Acts as a link between the CAN bus network for critical powertrain, anti-lock brake systems, electronic stability program systems and the network for body and interior modules.
2. Controls the wipers based on messages on the CAN B bus from the rain sensor module (if equipped).
3. Controls the adjustable pedal motor on non-memory equipped vehicles.
4. Controls back-up lamps.
5. Flashes lamps in response to turn signal, Remote Keyless Entry (RKE) and Vehicle Theft Security System (VTSS) inputs.
6. Illuminated approach feature that turns the headlamps on when the vehicle is unlocked with the Remote Keyless Entry (RKE) transmitter.
7. 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.
8. 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.
9. Operates the high-beam headlamps at reduced intensity by pulse-width modulation of the power supply to provide the daytime running lamps.
10. Protects the battery from discharge if the headlamps are left on, by automatically turning them off after eight minutes.
11. Provides ambient temperature sensor information.
12. Provides A/C pressure transducer information.
13. Provides brake fluid level information.
14. Provides washer fluid level information.
15. Provides the variable delay intermittent windshield and liftgate wiper time delay features, and the vehicle speed sensitive windshield wiper delay variation.
16. Sounds the horn in response to RKE and VTSS inputs.
17. Turns off the horn in the event of excessively long operation that could otherwise damage the horn.
18. Turns off the windshield washer motor after 10 seconds of continuous operation to protect the motor.
19. Controls headlamp washers (if equipped).
20. Provides wheel speed information on non-ABS equipped vehicles.
21. Stores vehicle configuration data.

The Memory Seat Module (MSM) receives battery current through a 25 amp circuit breaker in the Power Distribution Center (PDC) so that the memory system remains operational, regardless of the ignition switch position. When the driver memory switch button is pushed, a resistance signal is sent to the MSM via the Controller Area Network (CAN) bus circuit. The MSM is responsible for the 12v battery feed and ground path to the power seat adjuster motor and other memory system components.

The MSM receives memory set/position switch input through the CAN bus circuit. The MSM also receives hard wired input from the hall effect sensors, mounted on each of the driver power seat adjuster motors and the driver side view mirror motor. The programmed software in the module allows it to know where the seat, adjustable pedals, and steering column tilt/telescope are located in its designed travel by a pulse count generated from the hall effect sensors. This way, when the memory switch is depressed the module will power these components until the correct preset location is achieved. The module will prevent the seat memory recall function from being initiated, if the transmission gear selector lever is not in the Park position, or if the vehicle is moving. These inputs are monitored over the Controller Area Network (CAN) bus circuit by the MSM.

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.

The MSM performs the following functions

1. Positions the driver power seat (vertical, horizontal, and recliner positions).
2. Positions the power adjustable pedals.
3. Positions the power tilt/telescopic steering column positions.
4. Sends the memory save or recall (#1 or #2) command over the CAN data bus circuit to the other memory system components, radio station pre-sets and power mirror positions.
5. Provides for "linking" the key FOBs to memory.
6. Provides for the easy entry/exit feature.
7. Provides the tilt mirrors in reverse feature.

When a memory button is pressed (#1 or #2) on the memory switch, the Driver Door Module (DDM) sends a recall message to the MSM. The MSM will then position the memory system components to the preprogrammed location/setting. When the Remote Keyless Entry (RKE) Transmitter button is pressed, depending on which transmitter (#1 or #2), the SKREEM (RKE Receiver) sends the recall request and FOB number (#1 or #2) data message. This RKE transmitter function depends on if the MSM is programmed to trigger the recall (linked FOBs).

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 any position other than park or the seat belt is latched.

A key FOB is "linked" to a memory setting by pressing the "set" button and then pressing either the memory "1" or "2" button within 5 seconds of pressing the set button, then by pressing the "lock" button on the selected key FOB.

The memory system "Easy Entry and /Exit" feature provides the driver with more room to enter or exit the vehicle. When the seat is in a memorized position, it will move rearward 55 millimeters or to the end of its travel, whichever occurs first, when the key is removed from the ignition switch lock cylinder. This is a customer programmable feature of the overhead console. The seat will return to the memory position when the driver turns the vehicle's ignition switch out of the LOCK position.

The memory system "Tilt in Reverse" feature tilts the outside mirrors down a fixed, incremental angle when the vehicle is shifted into REVERSE with the ignition switch in the RUN position. This feature provides the customer with a better view of the ground and vehicle in the area of the rear tires when backing up. The mirrors move back to their previous position when the vehicle is shifted out of REVERSE.

The memory system "learns" the seat and adjustable pedal motor maximum end positions when the motor reaches the limit of travel in any direction and stalls. Subsequently, movement will stop just short of that position to avoid extra stress on the motors and mechanisms. If the system learned a maximum position as a result of an obstruction, as for instance if a large object was placed on the floor behind the seat, the system can relearn the "true" maximum position through manually operating the power seat after the obstruction is removed.

Note. It is normal for the power accessories contained in the memory system to stop at the maximum "learned" position and then continue to the "true" maximum position when the control switch is released and then applied in the same direction a second time.

Certain functions and features of the memory system rely upon resources shared with other electronic modules in the vehicle over the Controller Area Network (CAN) bus. The CAN bus allows the sharing of sensor information. This helps to reduce wire harness complexity, internal controller hardware, and component sensor current loads. At the same time, this system provides increased reliability, enhanced diagnostics, and allows the addition of many new feature capabilities. For diagnosis of these electronic modules or of the CAN bus, the use of a scan tool and the proper diagnostic information are needed.

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.

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).

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

1. Also refer to Modes of Operation.

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 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. A/C request
2. Auto shutdown (ASD) sense
3. Battery temperature
4. Battery voltage
5. Brake switch
6. J1850 bus circuits
7. Camshaft position sensor signal
8. Crankshaft position sensor
9. Data link connections for DRB scan tool
10. Engine coolant temperature sensor
11. Five volts (primary)
12. Five volts (secondary)
13. Fuel level
14. Generator (battery voltage) output
15. Ignition circuit sense (ignition switch in on/off/crank/run position)
16. Intake manifold air temperature sensor
17. Leak detection pump (switch) sense (if equipped)
18. Manifold absolute pressure (MAP) sensor
19. Oil pressure
20. Overdrive/override switch
21. Oxygen sensors
22. Park/neutral switch (auto. trans. only)
23. Power ground
24. Sensor return
25. Signal ground
26. Speed control multiplexed single wire input
27. Throttle position sensor
28. Transmission governor pressure sensor
29. Transmission temperature sensor
30. Vehicle speed (from ABS module)

Note. PCM Outputs

1. A/C clutch relay
2. Auto shutdown (ASD) relay
3. J1850 (+/-) circuits for: speedometer, voltmeter, fuel gauge, oil pressure gauge/lamp, engine temp. gauge and speed control warn. lamp
4. Data link connection for DRBIII(R) scan tool
5. EGR valve control solenoid (if equipped)
6. EVAP canister purge solenoid
7. Fuel injectors
8. Fuel pump relay
9. Generator field driver (-)
10. Generator field driver (+)
11. Generator lamp (if equipped)
12. Idle air control (IAC) motor
13. Ignition coil
14. Leak detection pump
15. Malfunction indicator lamp (Check engine lamp). Driven through J1850 circuits.
16. Overdrive indicator lamp (if equipped). Driven through J1850 circuits.
17. Oxygen sensor heater relays (if equipped).
18. Radiator cooling fan relay (pulse width modulated)
19. Speed control source
20. Speed control vacuum solenoid
21. Speed control vent solenoid
22. Tachometer (if equipped). Driven through J1850 circuits.
23. Transmission convertor clutch circuit
24. Transmission 3-4 shift solenoid
25. Transmission relay
26. Transmission temperature lamp (if equipped)
27. 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.