Multifunction Electronic Module: Overview Ford Mustang V facelift

Principles of Operation

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

The SJB controls various systems by monitoring inputs from switches, sensors and messages sent from other modules on the Medium Speed Controller Area Network (MS-CAN). Based on the inputs received, the SJB activates outputs. For example, the SJB monitors the headlamp switch position. Based on this input, the SJB may provide voltage to the exterior lamps.

Field-Effect Transistor (FET) Protection

A 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 short circuit 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 is still 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 short circuit 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 DTC (the DTC related to the shorted circuit) automatically clears and the circuit function returns.

When each level is reached, the 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 short circuit DTC. DTC B106F cannot be cleared and the module must be replaced after the repair.

Normal Operation

The Smart Junction Box (SJB) controls the output of several vehicle systems by means of solid state drivers. A DTC sets when an overload occurs on any of these drivers. The module also tracks the number of repetitive faults on each of these circuits, and then it compares said number of overloads to 3 progressive thresholds established for each circuit. If the third threshold has not been met, the DTC for the affected circuit can be cleared by eliminating the fault, clearing the DTCs and then running a self-test.

At the point that each of the first 2 thresholds is met, DTC B106E sets along with a DTC related to the affected circuit. Once the final (third) threshold has been met, the affected output is permanently disabled, and DTC B106F sets, at which time the SJB must be replaced.

1. DTC B106E (Solid State Driver Disabled Due to Short Circuit) - a continuous DTC that sets when the SJB has disabled an output circuit due to a repetitive fault that overloads said circuit. A corresponding DTC for the circuit in question is also set.
2. DTC B106F (Module Disabled Due to External Fault) - a continuous DTC that sets when the SJB has permanently disabled one or more output functions due to a repetitive circuit overload. DTC B1342 also sets at this time.

When DTC B1342 is set because the module has reached a third threshold and the SJB has permanently disabled an output, no DTCs can be cleared from the SJB . Using the module self-test to confirm a repair is not possible and a measurement using a digital multimeter of the affected output circuit is required to make sure the fault condition no longer exists.

This pinpoint test is intended to diagnose the following

1. Output circuit short
2. SJB

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

This pinpoint test is intended to diagnose the following

1. Charging system concern
2. SJB

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

This pinpoint test is intended to diagnose the following

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

1. DTC U0155 (Lost Communication With Instrument Panel Cluster (IC) Control Module) - a continuous DTC that sets when the SJB does not receive messaged data (loses communication) from the Instrument Panel Cluster (IPC) for longer than 5 minutes.

This pinpoint test is intended to diagnose the following

1. Communication network concern
2. SJB
3. IPC

The Body Control Module B (BCM-B) controls various systems by monitoring inputs from switches, sensors and messages sent from other modules on the Medium Speed Controller Area Network (MS-CAN). Based on the inputs received, the BCM-B activates outputs. For example, the BCM-B monitors the stoplamp switch and messages received from the Smart Junction Box (SJB) regarding ignition state and door ajar status. Based on this input, the BCM-B may provide voltage to the stoplamps or activate the ambient lighting.

A 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 BCM-B utilizes an FET protective circuit strategy for many of its outputs (for example, a stoplamp 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 short circuit 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 is still 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 short circuit 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 U1000:00 and the associated DTC (the DTC related to the shorted circuit) automatically clears and the circuit function returns.

When each level is reached, the DTC associated with the short circuit sets along with DTC U1000:00. 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 U1000:00 and U3000:49 set along with the associated short circuit DTC. DTC U3000:49 cannot be cleared and the module must be replaced after the repair.

1. DTC P2533:14 (Ignition Switch Run/Start Position Circuit: Circuit Short To Ground Or Open) - an on-demand DTC that sets when the BCM-B detects no voltage from the run/start circuit.

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. BCM-B
4. SJB

Scheme 83

Scheme 84

1. E1 CHECK THE RUN/START CIRCUIT FOR VOLTAGE Ignition OFF. Disconnect: BCM-B C4368a. Ignition ON. Measure the voltage between the BCM-B C4368a-7, circuit CBP35 (YE/GY), harness side and ground. Is the voltage greater than 10 volts? Yes: Go to E4 . No: VERIFY the SJB fuse 35 (10A) is OK. If OK, Go to E2 . If not OK, Refer to the «SYSTEM WIRING DIAGRAMS»(ref-395056) article to identify the possible causes of the circuit short.
2. E2 CHECK THE RUN/START CIRCUIT FOR AN OPEN Ignition OFF. Disconnect: SJB C2280d. Measure the resistance between the BCM-B C4368a-7, circuit CBP35 (YE/GY), harness side and the SJB C2280d-23, circuit CBP35 (YE/GY), harness side. Is the resistance less than 5 ohms? Yes: Go to E3 . No: REPAIR circuit CBP35 (YE/GY) for an open. CLEAR the DTCs. REPEAT the self-test.
3. E3 CHECK FOR CORRECT BCM-B OPERATION Disconnect the BCM-B connectors. Check for: corrosion damaged pins pushed-out pins Connect the BCM-B connectors and make sure they seat correctly. Operate the system and verify the concern is still present. Is the concern still present? Yes: INSTALL a new BCM-B . REFER to «BODY CONTROL MODULE B (BCM-B)»(ref-439796-S33537160262011120900000) in this service information. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation. No: The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
4. E4 CHECK FOR CORRECT BCM-B OPERATION Disconnect the BCM-B connectors. Check for: corrosion damaged pins pushed-out pins Connect the BCM-B connectors and make sure they seat correctly. Operate the system and verify the concern is still present. Is the concern still present? Yes: INSTALL a new BCM-B . REFER to «BODY CONTROL MODULE B (BCM-B)»(ref-439796-S33537160262011120900000) in this service information. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation. No: The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.

1. DTC U0140:87 (Lost Communication With Body Control Module: Missing Message) - a continuous memory DTC set by the BCM-B if data messages received from the SJB over the Medium Speed Controller Area Network (MS-CAN) are missing for 5 seconds or longer.

This pinpoint test is intended to diagnose the following

1. Communication network concern
2. BCM-B
3. SJB

1. DTC U0155:87 (Lost Communication With Instrument Panel Cluster (IPC) Control Module: Missing Message) - a continuous memory DTC set by the BCM-B if data messages received from the IPC over the Medium Speed Controller Area Network (MS-CAN) are missing for longer than 5 seconds.

This pinpoint test is intended to diagnose the following

1. Communication network concern
2. BCM-B
3. IPC

The Body Control Module B (BCM-B) 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.

At the each threshold, DTC U1000:00 sets along with the DTC associated with the affected circuit.

1. DTC U1000:00 (Solid State Driver Protection Activated - Driver Disabled: No Sub Type Information) - a continuous DTC that sets when the BCM-B has disabled an output circuit due to a repetitive fault that overloads said circuit. A corresponding DTC for the circuit in question is also set.

When DTC U3000:49 is set because the module has reached a third threshold and the BCM-B has permanently disabled an output, a measurement using a digital multimeter of the affected output circuit is required to make sure the fault condition no longer exists.

This pinpoint test is intended to diagnose the following

1. Output circuit short
2. BCM-B

1. DTC U3003:62 (Battery Voltage: Signal Compare Failure) - a continuous and on-demand DTC that sets when the BCM-B detects battery voltage 1.5 volts above or below specific thresholds.

This pinpoint test is intended to diagnose the following

1. Wiring, terminals or connectors
2. High circuit resistance
3. Charging system concern
4. BCM-B