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Home >> Chrysler >> 2011 >> 300 C, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1639 (66RFE Automatic Transmission - DTCS P0871 To U1449 - 2500 Hd) >> DTC Troubleshooting >> P1794-Speed Sensor Ground Error >> Diagnostic Test

Diagnostic Test

WARNING: This page is about a different car, the 2017 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. Start the Engine with the 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.
    2. Remove the Starter Relay.
      CAUTION:

      Removal of the Starter Relay will prevent the vehicle from being started in gear.

      WARNING:

      The Starter Relay must be removed. Failure to do so can result in possible serious or fatal injury.

    3. Install the Transmission Simulator (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. Turn the 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 
    1. Turn the Ignition OFF.
    2. Disconnect the PCM C1 harness connector.
      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 GPEC Diagnostic Adaptor to perform the diagnosis.

    3. Important:  The GPEC Diagnostic Adaptor can add up to 1.5 Ohms of resistance to the circuit.
    4. Connect the (special tool #10436, Adapter, GPEC Diagnostic) to the appropriate PCM harness connector.
    5. Disconnect the Transmission Simulator (special tool #8333B, Simulator, Transmission).
    6. 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 GPEC Diagnostic Adaptor.

      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 
    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 
    1. Turn the Ignition ON, Engine not running.
    2. 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 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.