Pinpoint Test A: DTC C1445 - Vehicle Speed Signal Circuit Failure

WARNING: This page is about a different car, the 2006 Mercury Grand Marquis and 2006 Ford Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.

CAUTION: The Flex Probe Kit must be used for all test connections. Use of standard multimeter probes may damage wiring terminals.

A1 ISOLATE THE POWERTRAIN CONTROL MODULE (PCM)
- Refer to INTRODUCTION - GASOLINE article to determine if there are any vehicle speed signal faults related to the PCM.
- Are there any PCM related faults?
Yes : REPAIR the source of the faults as instructed in the INTRODUCTION - GASOLINE article.

No : Go to A2.
A2 CHECK THE VEHICLE SPEED SIGNAL CIRCUIT FOR AN OPEN
- Disconnect: Powertrain Control Module (PCM) C175t.
- Disconnect: Variable Assist Power Steering (VAPS) Module C2231b (without air suspension).
- Disconnect: Air Suspension Module C2131b (with air suspension).
- For vehicles without air suspension , measure the resistance between PCM C175t-37, circuit 679 (GY/BK), harness side and VAPS module C2231b-13, circuit 679 (GY/BK), harness side.
  
  Fig 1: Measuring Resistance Between PCM C175T-37, Circuit 679 (GY/BK) And VAPS Module C2231B-13, Circuit 679 (GY/BK)
  Courtesy of FORD MOTOR CO.
- For vehicles with air suspension , measure the resistance between the PCM C175t-37, circuit 679 (GY/BK), harness side and the air suspension module C2131b-7, circuit 679 (GY/BK), harness side.
  
  Fig 2: Measuring Resistance Between PCM C175T-37, Circuit 679 (GY/BK) And Air Suspension Module C2131B-7, Circuit 679 (GY/BK)
  Courtesy of FORD MOTOR CO.
- Are the resistances less than 5 ohms?
Yes : GO to A3.

No : REPAIR circuit 679 (GY/BK) for an open. CLEAR the DTC. REPEAT the self-test.
A3 CHECK THE VEHICLE SPEED SIGNAL CIRCUIT FOR A SHORT TO GROUND
- For vehicles without air suspension , measure the resistance between the VAPS module C2231b-13, circuit 679 (GY/BK), and ground.
  
  Fig 3: Measuring Resistance Between VAPS Module C2231B-13, Circuit 679 (GY/BK) And Ground
  Courtesy of FORD MOTOR CO.
- For vehicles with air suspension , measure the resistance between the air suspension module C2131b-7, circuit 679 (GY/BK), and ground.
  
  Fig 4: Measuring Resistance Between Air Suspension Module C2131B-7, Circuit 679 (GY/BK) And Ground
  Courtesy of FORD MOTOR CO.
- Are the resistances less than 5 ohms?
Yes : REPAIR circuit 679 (GY/BK) for a short to ground. CLEAR the DTC. REPEAT the self-test.

No : GO to A4.
A4 CHECK THE VEHICLE SPEED SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE
- For vehicles without air suspension , measure the voltage between the VAPS module C2231b-13, circuit 679 (GY/BK), and ground.
  
  Fig 5: Measuring Voltage Between VAPS Module C2231B-13, Circuit 679 (GY/BK) And Ground
  Courtesy of FORD MOTOR CO.
- For vehicles with air suspension , measure the voltage between the air suspension module C2131b-7, circuit 679 (GY/BK), and ground.
  
  Fig 6: Measuring Voltage Between Air Suspension Module C2131B-7, Circuit 679 (GY/BK) And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
Yes : REPAIR circuit 679 (GY/BK) for a short to voltage. CLEAR the DTC. REPEAT the self-test.

No : INSTALL a new air suspension or VAPS module. REFER to MULTIFUNCTION ELECTRONIC MODULES for vehicles equipped with air suspension or REFER to POWER STEERING for all other vehicles. CLEAR the DTCs. REPEAT the self-test.