Pinpoint Test U: The C-Cm Does Not Respond To The Scan Tool

WARNING: This page is about a different car, the 2013 Lincoln MKX and 2013 Ford Edge. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.

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

U1 CHECK THE C-CM VOLTAGE SUPPLY CIRCUITS FOR AN OPEN
- Ignition OFF.
- Disconnect: C-CM C1582.
- Ignition ON.
- Measure the voltage between the C-CM C1582-1, circuit SBB79 (WH/RD), harness side and ground, and the C-CM C1582-10, circuit CBB91 (BN), harness side and ground.
  
  Fig 1: Measuring Voltage Between C-CM C1582-1, Circuit SBB79 (WH/RD), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
  - YES : GO to U2.
  - No : VERIFY the Battery Junction Box (BJB) fuses 79 (5A) and 91 (10A) are OK. If OK, REPAIR the circuit in question. If not OK, REFER to the appropriate SYSTEM WIRING DIAGRAMS (Edge) article or SYSTEM WIRING DIAGRAMS (MKX) article to identify the possible causes of the circuit short. TEST the system for normal operation.
U2 CHECK THE C-CM GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: Negative Battery Cable.
- Measure the resistance between the C-CM C1582-4, circuit GD120 (BK/GN), harness side and ground.
  
  Fig 2: Measuring Resistance Between C-CM C1582-4, Circuit GD120 (BK/GN), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
  - YES : GO to U3.
  - No : REPAIR the circuit. CONNECT the negative battery cable. CLEAR the DTCs. TEST the system for normal operation.
U3 CHECK THE HS-CAN CIRCUITS BETWEEN THE C-CM AND THE DLC FOR AN OPEN
- Measure the resistance between the C-CM C1582-8, circuit VDB04 (WH/BU), harness side and the DLC C251-6, circuit VDB04 (WH/BU), harness side.
  
  Fig 3: Measuring Resistance Between C-CM C1582-8, Circuit VDB04 (WH/BU) And DLC C251-6, Circuit VDB04 (WH/BU), Harness Side
  Courtesy of FORD MOTOR CO.
- Measure the resistance between the C-CM C1582-7, circuit VDB05 (WH), harness side and the DLC C251-14, circuit VDB05 (WH), harness side.
  
  Fig 4: Measuring Resistance Between C-CM C1582-7, Circuit VDB05 (WH) And DLC C251-14, Circuit VDB05 (WH), Harness Side
  Courtesy of FORD MOTOR CO.
- Are the resistances less than 5 ohms?
  - YES : CONNECT the negative battery cable. GO to U4.
  - No : REPAIR the circuit in question. CONNECT the negative battery cable. CLEAR the DTCs. REPEAT the network test with the scan tool.
U4 CHECK FOR CORRECT C-CM OPERATION
- Disconnect the C-CM connector.
- Check for:
  - Corrosion
  - Damaged pins
  - Pushed-out pins
- Connect the C-CM connector and make sure it seats correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
  - YES : INSTALL a new C-CM. REFER to CRUISE CONTROL . 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.