Pinpoint Test F: DTC C1230 - Rear Axle Speed Sensor Input Circuit Failure

F1 CHECK FOR FAULT REPEATABILITY
- Connect the diagnostic tool.
- Enter the following diagnostic mode on the diagnostic tool: Clear Continuous DTCs.
- Drive the vehicle at least 6 km/h (10 mph).
- Enter the following diagnostic mode on the diagnostic tool: Retrieve and document continuous DTCs.
- Is DTC C1230 retrieved?
- Yes : GO to F2.
- No : If no DTC is retrieved, GO to F6.
If a different DTC is retrieved, refer to the ANTI-LOCK BRAKE SYSTEM (ABS) MODULE DIAGNOSTIC TROUBLE CODE (DTC) INDEX .
F2 CHECK THE REAR AXLE SPEED SENSOR COIL RESISTANCE AT THE ANTI-LOCK BRAKE SYSTEM (ABS) MODULE
- Key in OFF position.
- Install the EEC-IV 60-Pin Breakout Box.
- Measure the resistance between the EEC-IV 60-Pin Breakout Box pin 14 and the EEC-IV 60-Pin Breakout Box pin 6.
  
  Fig 1: Measuring Resistance Between Pin 14 And Pin 6
  Courtesy of FORD MOTOR CO.
- Is the resistance between 800 and 3500 ohms?
- Yes : GO to F4.
- No : GO to F3.
F3 DETERMINE THE LOCATION OF THE FAULT
- Disconnect: Rear Axle Speed Sensor C455.
- Measure the resistance between the 2 terminals of the rear axle speed sensor C455.
  
  Fig 2: Measuring Resistance Between 2 Terminals Of Rear Axle Speed Sensor C455
  Courtesy of FORD MOTOR CO.
- Is the resistance between 800 and 3500 ohms?
- Yes : REPAIR circuit 519 (LG/BK) and circuit 523 (RD/PK). TEST the system for normal operation.
- No : INSTALL a new rear axle speed sensor. REFER to REAR WHEEL SPEED SENSOR in this article. TEST the system for normal operation.
F4 CHECK THE REAR AXLE SPEED SENSOR CIRCUIT FOR A SHORT TO GROUND
- Measure the resistance between the EEC-IV 60-Pin Breakout Box pin 14 and ground; and between the EEC-IV 60-Pin Breakout Box pin 6 and ground.
  
  Fig 3: Checking The Rear Axle Speed Sensor Circuit For A Short To Ground
  Courtesy of FORD MOTOR CO.
- Are the resistances greater than 10,000 ohms?
- Yes : INSTALL a new ABS module. REFER to ANTI-LOCK BRAKE SYSTEM (ABS) MODULE in this article. TEST the system for normal operation.
- No : GO to F5.
F5 CHECK FOR AN AXLE SPEED SENSOR SHORT
- Disconnect: Rear Axle Speed Sensor C455.
- Measure the resistance between the rear axle speed sensor C455 terminals and ground.
  
  Fig 4: Measuring Resistance Between Rear Axle Speed Sensor C455 Terminals And Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance greater than 10,000 ohms?
- Yes : REPAIR circuit 519 (LG/BK) and circuit 523 (RD/PK). TEST the system for normal operation.
- No : INSTALL a new rear axle speed sensor. REFER to REAR WHEEL SPEED SENSOR in this article. TEST the system for normal operation.
F6 TEST FOR AN INTERMITTENT AXLE SPEED SENSOR FAULT
- Carry out the Sensor Failure test for the rear axle speed sensor. Refer to COMPONENT TEST - INTERMITTENT FAILURES .
- Did the rear axle speed sensor pass?
- Yes : System is OK.
- No : INSTALL a new rear axle speed sensor. REFER to REAR WHEEL SPEED SENSOR in this article. TEST the system for normal operation.