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Home >> Chrysler >> 2011 >> 300 C, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 968 (Powertrain Control Module (Pcm) - Electrical Diagnostics - 66RFE Automatic Transmission - 2500 Hd & 3500 Hd) >> Diagnosis And Testing >> P1794-Speed Sensor Ground Error >> Diagnostic Test

Diagnostic Test

WARNING: This page is about a different car, the 2015 RAM 3500 HD and 2015 RAM 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.
  1. CHECK IF THE DTC IS CURRENT 
    1. Engine Running, Shift lever in park.
    2. With the scan tool, read the Transmission Output and Input Speed Sensor states.

      Is the Output Speed Sensor reading twice the Input Speed Sensor reading?

      Yes 

      • Go To  2

      No 

      • Go To  6
  2. CHECK THE PCM AND WIRING 
    1. Turn the ignition OFF to the LOCK position.
    2. Remove the Ignition Switch Feed fuse from the TIPM.
      CAUTION:

      Removal of the Ignition Switch Feed fuse from the TIPM will prevent the vehicle from being started in gear.

      WARNING:

      The Ignition Switch Feed fuse must be removed from the TIPM. Failure to do so can result in possible serious or fatal injury.

    3. Install the (special tool #8333B, Simulator, Transmission).
    4. With the Transmission Simulator, set the Input/Output Speed selector switch to the "3000/1000" position. Turn the Input/Output Speed switch to "ON".
    5. Ignition ON, Engine Not Running.
    6. With the scan tool, monitor the Input and Output Speed Sensor state.

      Does the Input speed read 3000 RPM and the Output speed read 1000 RPM, within 50 RPM?

      Yes 

      • Go To  6

      No 

      • Go To  3
  3. (T13) SPEED SENSOR GROUND CIRCUIT OPEN 
    Fig 1: Checking Speed Sensor Ground Circuit For Open
    GC0090565Courtesy of CHRYSLER GROUP, LLC
    1. Turn the ignition OFF to the LOCK position.
    2. Disconnect the PCM C4 harness connector and connect the (special tool #8815A, Kit, NGC, 38 Position).
    3. Disconnect the (special tool #8333B, Simulator, Transmission).
      CAUTION:

      Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install the PCM Pinout Box and PCM Pinout Box Adapter to perform diagnosis.

    4. Measure the resistance of the (T13) Speed Sensor Ground circuit between both Input and Output Speed Sensor harness connectors and the appropriate terminal of the (special tool #8815A, Kit, NGC, 38 Position).

      Is the resistance above 5.0 ohms on any of the above measurements?

      Yes 

      No 

      • Go To  4
  4. (T13) SPEED SENSOR GROUND CIRCUIT SHORTED TO GROUND 
    Fig 2: Checking Speed Sensor Ground Circuit For Short To Ground
    GC0090567Courtesy of CHRYSLER GROUP, LLC
    1. Measure the resistance between ground and the (T13) Speed Sensor Ground circuit.

      Is the resistance below 5.0 ohms?

      Yes 

      No 

      • Go To  5
  5. (T13) SPEED SENSOR GROUND CIRCUIT SHORTED TO VOLTAGE 
    Fig 3: Checking Speed Sensor Ground Circuit For Short To Voltage
    GC0090563Courtesy of CHRYSLER GROUP, LLC
    1. Ignition ON, Engine Not Running.
    2. With the scan tool under TIPM, actuate the Transmission.
    3. Measure the voltage of the (T13) Speed Sensor Ground circuit.

      Is the voltage above 0.5 volts?

      Yes 

      No 

      • Using the schematics as a guide, check the Powertrain Control Module (PCM) terminals for corrosion, damage or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace and program the PCM in accordance with the Service Information. With the scan tool, perform a Quick Learn.
      • Perform the 66RFE TRANSMISSION VERIFICATION TEST. Refer to 66RFE TRANSMISSION VERIFICATION TEST .
  6. CHECK THE WIRING AND CONNECTORS 
    1. The conditions necessary to set this DTC are not present at this time.
    2. Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
    3. Wiggle the wires while checking for shorted and open circuits.
    4. With the scan tool, check the Event Data to help identify the conditions in which the DTC set.

      Were any problems found?

      Yes 

      No 

      • Test Complete.