Multifunction Electronic Modules: Overview Ford Expedition III

Principles of Operation

Note. The Smart Junction Box (SJB) is also known as the Generic Electronic Module (GEM).

Note. The time-out for the battery saver relay and the accessory delay relay (both are controlled by the SJB ) is 1 minute if the vehicle has less than 80 km (50 miles). Once the vehicle passes the approximate mileage threshold of 80 km (50 miles), the time out for both relays is 10 minutes, as described by the Owner's Literature. For the battery saver relay, refer to INTERIOR LIGHTING . For the accessory delay relay, refer to GLASS, FRAMES AND MECHANISMS .

The SJB communicates via the Medium Speed Controller Area Network (MS-CAN).

The SJB controls the following lock/unlock features

1. Remote Keyless Entry (RKE) transmitter lock/unlock
2. Panic alarm (button is part of the RKE transmitter)
3. Keyless entry keypad (if equipped)
4. Monitoring of the power door lock system
5. Power door lock system

The SJB controls the autolamp subsystem. The autolamp subsystem provides light-sensitive automatic on/off control of the headlamps and parking lamps. Refer to EXTERIOR LIGHTING .

The SJB controls the battery saver, delayed accessory function, the horn, and exterior and interior lighting.

The SJB controls the Tire Pressure Monitoring System (TPMS). The TPMS monitors the tire pressures of all road tires. If any tire becomes low on pressure, a visual warning appears in the IC . Refer to WHEELS & TIRES .

Field-Effect Transistor (FET) Protection

Field-Effect Transistor (FET) is a type of transistor that when used with module software can be used to monitor and control current flow on module outputs. The FET protection strategy is used to prevent module damage in the event of excessive current flow.

The SJB utilizes an FET protective circuit strategy for many of its outputs (for example, a headlamp output circuit). Output loads (current level) are monitored for excessive current (typically short circuits) and are shut down (turns off the voltage or ground provided by the module) when a fault event is detected. A continuous DTC is stored at the fault event and a cumulative counter is started.

When the demand for the output is no longer present, the module resets the FET circuit protection to allow the circuit to function. The next time the driver requests a circuit to activate that has been shut down by a previous short ( FET protection) and the circuit remains shorted, the FET protection shuts off the circuit again and the cumulative counter advances.

When the excessive circuit load occurs often enough, the module shuts down the output until a repair procedure is carried out. Each FET protected circuit has 3 predefined levels of short circuit tolerance based on the harmful effect of each circuit fault on the FET and the ability of the FET to withstand it. A module lifetime level of fault events is established based upon the durability of the FET . If the total tolerance level is determined to be 600 fault events, the 3 predefined levels would be 200, 400 and 600 fault events.

When each tolerance level is reached, the continuous DTC that was stored on the first failure cannot be cleared by a command to clear the continuous DTCs. The module does not allow this code to be cleared or the circuit restored to normal operation until a successful self-test proves that the fault has been repaired. After the self-test has successfully completed (no on-demand DTCs present), DTC B106E and the associated continuous DTC (the DTC related to the shorted circuit) automatically clears and the circuit function returns.

When the first or second level is reached, the continuous DTC (associated with the short circuit) sets along with DTC B106E. These DTCs can be cleared using the module on-demand self-test, then the Clear DTC operation on the scan tool (if the on-demand test shows the fault corrected). The module never resets the fault event counter to zero and continues to advance the fault event counter as short circuit fault events occur.

If the number of short circuit fault events reach the third level, then DTCs B106F and B1342 set along with the associated continuous DTC. This DTC cannot be cleared and the module must be replaced.

The SJB FET protected output circuits for the headlamp system are for the LH low beam output and the RH low beam output circuits.

Normal Operation

The Smart Junction Box (SJB) controls the output of several vehicle systems by means of solid state drivers. When an overload occurs on any of these drivers, a DTC sets. The module also tracks the number of repetitive faults on each of these circuits. The module compares this number of overloads to 3 progressive thresholds established for each circuit. If the 3 thresholds have not been exceeded, then the DTC of the affected circuit can be cleared by eliminating the fault, then clearing the DTCs and running the self-test. At the point that each of the first 2 thresholds are exceeded, DTC B106E sets along with the DTC relating to the affected circuit. Once the final threshold has been exceeded, the affected output is permanently disabled, and DTC B106F sets along with DTC B1342, at which time the SJB must be replaced.

1. DTC B106E (Solid State Driver Disabled Due to Short Circuit) - sets when the SJB has disabled a circuit due to a repetitive fault causing a circuit overload. A corresponding DTC for the circuit in question also sets.
2. DTC B106F (Module Disabled Due to External Fault) - sets when one or more output functions are permanently disabled due to a repetitive circuit overload fault. DTC B106F sets with DTC B106E. When DTC B106F is present, a new SJB must be installed after the fault condition has been corrected.

This pinpoint test is intended to diagnose the following

1. Output circuit short to ground or voltage
2. SJB

The Smart Junction Box (SJB) monitors the voltage from the battery to determine if it goes above or below specific thresholds and sets DTC B1317 in continuous memory if the SJB detects high battery voltage above 15 volts on circuit SDC04.

1. DTC B1317 (Battery Voltage High) - a continuous memory DTC that sets when the SJB detects battery voltage above 15 volts on circuit SDC04.

This pinpoint test is intended to diagnose the following

1. Charging system concern
2. SJB

The Smart Junction Box (SJB) monitors the voltage from the battery to determine if it goes above or below specific thresholds and sets DTC B1318 in continuous memory if the SJB detects low battery voltage below 10 volts on circuit SDC04.

1. DTC B1318 (Battery Voltage Low) - a continuous memory DTC that sets when the SJB detects battery voltage below 10 volts on circuit SDC04.

This pinpoint test is intended to diagnose the following

1. Wiring, terminals or connectors
2. High circuit resistance
3. SJB

The Smart Junction Box (SJB) and the Instrument Cluster (IC) communicate using the Medium Speed Controller Area Network (MS-CAN). Messages are exchanged between the modules on the MS-CAN for the purposes of determining what functions are being carried out.

1. DTC U0155 (Lost Communication With Instrument Panel Cluster ( IC ) Control Module) - set by the SJB whenever it loses communication with the IC if the ignition is not in the START position, the SJB supply voltage is greater than 10.5 volts and the ignition must be in the ON position for a minimum of 5 seconds.

This pinpoint test is intended to diagnose the following

1. Module communication
2. SJB
3. IC

Note. The Smart Junction Box (SJB) is also known as the Generic Electronic Module (GEM).

The Driver Seat Module (DSM) is on the Medium Speed Controller Area Network (MS-CAN) communication network.

The DSM controls the memory power exterior mirrors. This feature allows the driver to program personalized mirror positions. Once the driver has stored a mirror position, the driver can recall the setting by pressing the corresponding memory switch or by using a programmed Remote Keyless Entry (RKE) transmitter. Refer to REAR VIEW MIRRORS .

The memory driver seat feature allows the driver to program a personalized seat position that can be recalled using the memory switches or the RKE transmitter. Refer to SEATING .

The memory adjustable pedals and memory power tilt column are also controlled by the DSM . These systems permit the adjustment of the brake, the accelerator pedals and the tilt column by pressing the desired memory set switch or by using a programmed RKE transmitter. Refer to BRAKE SYSTEM - GENERAL INFORMATION .

The power fold mirrors are also controlled by the DSM . This system permits the mirrors to be folded in or out using the power mirror switch.

The Driver Seat Module (DSM) controls the output of several vehicle systems by means of solid state drivers. When an overload occurs on any of these drivers, a DTC sets. The module also tracks the number of repetitive faults on each of these circuits. The module compares this number of overloads to 3 progressive thresholds established for each circuit. If the 3 thresholds have not been exceeded, then the DTC of the affected circuit can be cleared by eliminating the fault, then clearing the DTCs and running the self-test. At the point that each of the first 2 thresholds are exceeded, DTC B106E sets along with the DTC relating to the affected circuit. Once the final threshold has been exceeded, the affected output is permanently disabled, and DTC B106F sets along with DTC B1342, at which time the DSM must be replaced.

1. DTC B106E (Solid State Driver Disabled Due To Short Circuit) - sets when the DSM has disabled a circuit due to a repetitive fault causing a circuit overload. A corresponding DTC for the circuit in question also sets.
2. DTC B106F (Module Disabled Due to External Fault) - sets when one or more output functions are permanently disabled due to a repetitive circuit overload fault. DTC B106F sets with DTC B1342. When DTC B106F is present, a new DSM must be installed after the fault condition has been corrected.

This pinpoint test is intended to diagnose the following

1. Output circuit short to ground or voltage
2. DSM

The Driver Seat Module (DSM) monitors the voltage from the battery to determine if the voltage is above or below specific thresholds. The DSM sets DTC B1317 in continuous memory if the DSM detects high battery voltage above 15 volts on circuit SBB74.

1. DTC B1317 (Battery Voltage High) - a continuous memory DTC that sets when the DSM detects battery voltage above 15 volts on circuit SBB74.

This pinpoint test is intended to diagnose the following

1. Charging system concern
2. DSM

The Driver Seat Module (DSM) monitors the voltage from the battery to determine if the voltage is above or below specific thresholds. The DSM sets DTC B1318 in continuous memory if the DSM detects low battery voltage below 10 volts on circuit SBB74.

1. DTC B1318 (Battery Voltage Low) - a continuous memory DTC that sets when the DSM detects battery voltage below 10 volts on circuit SBB74.

This pinpoint test is intended to diagnose the following

1. Wiring, terminals or connectors
2. High circuit resistance
3. DSM

The Driver Seat Module (DSM) and the Smart Junction Box (SJB) communicate using the Medium Speed Controller Area Network (MS-CAN). Messages are exchanged between the modules on the MS-CAN for the purposes of determining what functions are being carried out.

1. DTC U0140 (Lost Communication With Body Control Module ( GEM )) - set by the DSM whenever it has lost communication to the SJB for 15 seconds or longer as long as the module voltage is between 10 and 15 volts.

This pinpoint test is intended to diagnose the following

1. Module communication
2. DSM
3. SJB

The Driver Seat Module (DSM) and the Instrument Cluster (IC) communicate using the Medium Speed Controller Area Network (MS-CAN). Messages are exchanged between the modules on the MS-CAN for the purposes of determining what functions are being carried out.

1. DTC U0155 (Lost Communication With Instrument Panel Cluster ( IC ) Control Module) - set by the DSM whenever it has the ignition status message present and the DSM has lost communication to the IC for 15 seconds or longer and the DSM voltage is between 10 and 15 volts.

This pinpoint test is intended to diagnose the following

1. Module communication
2. DSM
3. IC