Pinpoint Test S: No Controller Area Network (Can) Communication

WARNING: This page is about a different car, the 2005 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.

S1 CHECK THE DATA LINK CONNECTOR (DLC) C251 FOR DAMAGE
- Inspect the DLC C251 for damage.
- Is the DLC C251 OK?
- Yes : GO to S2.
- No : REPAIR the DLC C251. CARRY OUT the diagnostic tool data link test.
S2 CHECK THE CAN MODULE CONNECTORS FOR DAMAGE
- Key in OFF position.
- Disconnect: Anti-Lock Brake System (ABS) Module C135.
- Disconnect: Powertrain Control Module (PCM) C175b.
- Inspect the connectors for damage.
- Are the connectors OK?
- Yes : GO to S3.
- No : REPAIR the module connector in question. CARRY OUT the diagnostic tool data link test.
S3 CHECK THE CAN CIRCUITS 1827 (WH/LG) AND 1828 (PK/LG) FOR A SHORT TO VOLTAGE
- Key in ON position.
- Measure the voltage between the DLC C251 pin 6, circuit 1827 (WH/LG), harness side and ground; and between the DLC C251 pin 14, circuit 1828 (PK/LG), harness side and ground.
  
  Fig 1: Measuring Voltage Between DLC C251 Pin 6, Circuit 1827 (WH/LG), Harness Side And Ground; And Between DLC C251 Pin 14, Circuit 1828 (PK/LG), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Is any voltage present?
- Yes : REPAIR the circuit in question. CARRY OUT the diagnostic tool data link test.
- No : GO to S4.
S4 CHECK THE CAN CIRCUITS 1827 (WH/LG) AND 1828 (PK/LG) FOR A SHORT TO GROUND
- Measure the resistance between the DLC C251 pin 6, circuit 1827 (WH/LG), harness side and ground; and between the DLC C251 pin 14, circuit 1828 (PK/LG), harness side and ground.
  
  Fig 2: Measuring Resistance Between DLC C251 Pin 6, Circuit 1827 (WH/LG), Harness Side And Ground; And Between DLC C251 Pin 14, Circuit 1828 (PK/LG), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Are the resistances less than 5 ohms?
- Yes : GO to S5.
- No : REPAIR the circuit in question. CARRY OUT the diagnostic tool data link test.
S5 CHECK CIRCUITS 1827 (WH/LG) AND 1828 (PK/LG) BETWEEN THE ANTI-LOCK BRAKE SYSTEM (ABS) MODULE C135 AND THE DLC C251 FOR AN OPEN
- Measure the resistance between the ABS module C135 pin 18, circuit 1827 (WH/LG), harness side and the DLC C251 pin 6, circuit 1827 (WH/LG), harness side.
  
  Fig 3: Measuring Resistance Between ABS Module C135 Pin 18, Circuit 1827 (WH/LG), Harness Side And DLC C251 Pin 6, Circuit 1827 (WH/LG), Harness Side
  Courtesy of FORD MOTOR CO.
- Measure the resistance between the ABS module C135 pin 28, circuit 1828 (PK/LG), harness side and the DLC C251 pin 14, circuit 1828 (PK/LG), harness side.
  
  Fig 4: Measuring Resistance Between ABS Module C135 Pin 28, Circuit 1828 (PK/LG), Harness Side And DLC C251 Pin 14, Circuit 1828 (PK/LG), Harness Side
  Courtesy of FORD MOTOR CO.
- Are the resistances less than 5 ohms?
- Yes : GO to S6.
- No : REPAIR the circuit in question. CARRY OUT the diagnostic tool data link test.
S6 CHECK CIRCUITS 1827 (WH/LG) AND 1828 (PK/LG) BETWEEN THE PCM C175B AND THE DLC C251 FOR AN OPEN
- Measure the resistance between the PCM C175b pin 11, circuit 1827 (WH/LG), harness side and the DLC C251 pin 6, circuit 1827 (WH/LG), harness side.
  
  Fig 5: Measuring Resistance Between PCM C175b Pin 11, Circuit 1827 (WH/LG), Harness Side And DLC C251 Pin 6, Circuit 1827 (WH/LG), Harness Side
  Courtesy of FORD MOTOR CO.
- Measure the resistance between the PCM C175b pin 23, circuit 1828 (PK/LG), harness side and the DLC C251 pin 14, circuit 1828 (PK/LG), harness side.
  
  Fig 6: Measuring Resistance Between PCM C175b Pin 23, Circuit 1828 (PK/LG), Harness Side And DLC C251 Pin 14, Circuit 1828 (PK/LG), Harness Side
  Courtesy of FORD MOTOR CO.
- Are the resistances less than 5 ohms?
- Yes : GO to S7.
- No : REPAIR the circuit in question. CARRY OUT the diagnostic tool data link test.
S7 CHECK THE CAN WITH A SUBSTITUTED POWERTRAIN CONTROL MODULE (PCM)
- Key in OFF position.
- Connect: ABS Module C135.
- INSTALL a known good PCM. Refer to ELECTRONIC ENGINE CONTROLS .
- Key in ON position.
- Enter the following diagnostic mode on the diagnostic tool: Data Link Diagnostics Test.
- Is system passed obtained?
- Yes : GO to S9.
- No : INSTALL the original PCM. GO to S8.
S8 CHECK FOR CORRECT ABS MODULE OPERATION
- Disconnect all the ABS module connectors.
- Check for:
  - corrosion
  - pushed-out pins
- Connect all the ABS module 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 ABS module. Refer to ANTI-LOCK CONTROL . CLEAR the DTCs. REPEAT the self-test. CARRY OUT the diagnostic tool data link test.
- 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. CARRY OUT the diagnostic tool data link test.
S9 CHECK FOR CORRECT PCM OPERATION
- Disconnect all the PCM connectors.
- Check for:
  - corrosion
  - pushed-out pins
- Connect all the PCM 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 PCM. Refer to ELECTRONIC ENGINE CONTROLS . CLEAR the DTCs. REPEAT the self-test. CARRY OUT the diagnostic tool data link test.
- 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. CARRY OUT the diagnostic tool data link test.