Pinpoint Test J: The BECM Does Not Respond To The Scan Tool

WARNING: This page is about a different car, the 2010 Mercury Milan, 2010 Lincoln MKZ, and 2010 Ford Fusion. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Failure to disconnect the battery when instructed will result in false resistance readings. Refer to BATTERY, MOUNTING AND CABLES .

J1 CHECK THE POWER TO THE BECM

WARNING: To prevent the risk of high-voltage shock, always follow precisely all warnings and service instructions, including instructions to depower the system. The high-voltage hybrid system utilizes approximately 300 volts DC, provided through high-voltage cables to its components and modules. The high-voltage cables and wiring are identified by orange harness tape or orange wire covering. All high-voltage components are marked with high-voltage warning labels with a high-voltage symbol. Failure to follow these instructions may result in serious personal injury or death.

WARNING: Always wear high-voltage insulated safety gloves with leather outer gloves and a face shield when servicing the battery pack sensor module (BPSM) and never remove the high-voltage BPSM connector unless directed by a service procedure. High voltage is present at the BPSM at all times, even with service disconnect plug removal . Depowering the system will not remove voltage from the BPSM connector with the orange harness. Follow all service instructions. Failure to follow these instructions may result in serious personal injury or death.

Ignition OFF.
Disconnect: BECM C4237a.
Ignition ON.

Measure the voltage between the BECM , harness side and ground as follows:

VOLTAGE REFERENCE TABLE

Connector-Pin	Circuit
C4237a-41	CBB48 (GY/YE)
C4237a-42	CBB48 (GY/YE)
C4237a-43	CBB48 (GY/YE)
C4237a-47	SBB17 (RD)
C4237a-48	SBB17 (RD)

Fig 1: Measuring Voltage Between BECM Harness Side And Ground

Courtesy of FORD MOTOR CO.

Are the voltages greater than 10 volts?

Yes : GO to J2.
No : VERIFY the Battery Junction Box (BJB) fuse 17 (10A) or 48 (20A) are OK. If OK, REPAIR the circuit in question. If not OK, REFER to the appropriate SYSTEM WIRING DIAGRAMS article to identify the possible causes of the circuit short. CLEAR the DTCs. REPEAT the network test with the scan tool.

J2 CHECK THE BECM GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: Negative Battery Cable.
- Measure the resistance between the BECM C4237a-49, circuit GD126 (BK/WH), harness side and ground; and between the BECM C4237a-50, circuit GD126 (BK/WH), harness side and ground
  
  Fig 2: Checking BECM Ground Circuit For An Open
  Courtesy of FORD MOTOR CO.
- Are the resistances less than 5 ohms?
- Yes : GO to J3.
- No : REPAIR the circuit in question. CONNECT the negative battery cable. CLEAR the DTCs. REPEAT the network test with the scan tool.
J3 CHECK THE HS-CAN CIRCUITS BETWEEN THE BECM AND THE DLC FOR AN OPEN
- Measure the resistance between the BECM C4237a-22, circuit VDB04 (WH/BU), harness side and the DLC C251-6, circuit VDB04 (WH/BU), harness side.
  
  Fig 3: Checking HS-CAN Circuits Between BECM And DLC For An Open (1 Of 2)
  Courtesy of FORD MOTOR CO.
- Measure the resistance between the BECM C4237a-11, circuit VDB05 (WH), harness side and the DLC C251-14, circuit VDB05 (WH), harness side.
  
  Fig 4: Checking HS-CAN Circuits Between BECM And DLC For An Open (2 Of 2)
  Courtesy of FORD MOTOR CO.
- Are the resistances less than 5 ohms?
- Yes : CONNECT the negative battery cable. GO to J4.
- No : REPAIR the circuit in question. CONNECT the negative battery cable. CLEAR the DTCs. REPEAT the network test with the scan tool.
J4 CHECK FOR CORRECT BECM OPERATION

NOTE: Do not disconnect the high voltage cables or connectors in the following step.

Disconnect the BECM LOW VOLTAGE connectors.
Check for:
- corrosion
- damaged pins
- pushed-out pins
Connect the BECM LOW VOLTAGE connectors and make they seat correctly.
Operate the system and verify the concern is still present.
Is the concern still present?

Yes : INSTALL a new BECM . REFER to HIGH VOLTAGE TRACTION BATTERY . CLEAR the DTCs. REPEAT the network test with the scan tool.
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 network test with the scan tool.