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Home >> Jeep >> 2021 >> Grand Cherokee L Laredo, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 24 (8HP75 Automatic Transmission - DTCS P0219-00 To P1D78-00) >> Diagnosis And Testing >> P0816-00: Downshift Switch Circuit >> Diagnostic Test

Diagnostic Test

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  1. READ AND RECORD DTCS AND ENVIRONMENTAL DATA - ERASE DTCS AND CHECK FOR DTC TO RETURN 
    NOTE:

    With the scan tool, read Transmission Control Module (TCM) DTCs and record the Event and Environmental Data on the repair order as it may be needed to determine the root cause of this DTC. It may be very difficult to reset this DTC so this step is very important.

    1. With the scan tool, read DTCs in all Electronic Control Units (ECUs) and record on the repair order.
    2. With the scan tool, run a vehicle Scan Report, or record the Environmental Data related to the DTCs.
    3. With the scan tool, erase all DTCs.
    4. Turn the ignition off for a minimum of 10.0 seconds.
    5. Turn the ignition on.
    6. Using the recorded Environmental Data and the When Monitored Conditions above, operate the vehicle in the conditions that set the DTC.
    7. With the scan tool, read DTCs.

    Did the DTC return?

    Yes 

    • Go To  2

    No 

  2. CHECK THE UPSHIFT (+) SWITCH CIRCUIT VOLTAGE 
    1. Turn the ignition off.
    2. Disconnect the paddle switches.
    3. Connect the negative lead of a DVOM to the (Z92) ground terminal and the positive lead to the (T830) Signal circuit.
    4. Turn the ignition to the Run position.

      What is the result?

      There is 4.8 to 5.2 volts present on the (T830) Signal circuit. 

      • Go To  8

      There is 4.7 volts or less present on the (T830) Signal circuit. 

      • Go To  3

      There is 5.3 volts or greater present on the (T830) Signal circuit. 

      Go to  6

  3. CHECK THE (T830) SIGNAL CIRCUIT VOLTAGE 
    1. Disconnect the paddle switches.
    2. Using a DVOM, connect the negative lead to a known good ground and connect the positive lead to the (T830) Signal circuit at the TCM side harness connector.

      Is there 4.8 to 5.2 volts present on the (T830) Tap Shift Signal circuit?

      Yes 

      • Go To  7

      No 

      • Go To  4
  4. CHECK THE (T830) SIGNAL CIRCUIT FOR AN OPEN OR HIGH RESISTANCE 
    1. Turn the ignition off.
    2. Disconnect the TCM harness connector.
    3. Disconnect the Paddle Switch connector.
    4. Measure the resistance of the (T830) Signal circuit.

      Is the resistance below 3.0 Ohms?

      Yes 

      • Go To  5

      No 

      • Repair the (T830) Signal circuit for an open or high resistance.
      • Perform the TRANSMISSION VERIFICATION TEST. Refer to TRANSMISSION VERIFICATION TEST .
  5. CHECK THE (T830) SIGNAL CIRCUIT FOR A SHORT TO GROUND 
    1. Turn the ignition off.
    2. Disconnect the TCM harness connector.
    3. Disconnect the Paddle Switch connector.
    4. Measure the resistance of the (T830) Signal circuit and ground.

      Is there continuity between the (T830) Signal circuit and ground?

      Yes 

      No 

  6. CHECK THE (T830) SIGNAL CIRCUIT FOR A SHORT TO ANOTHER CIRCUIT 
    1. Turn the ignition off.
    2. Disconnect the TCM harness connector.
    3. Disconnect the Paddle Switch connector.
    4. Measure the resistance of the (T830) Signal circuit and all other circuits at the TCM harness connector.

      Is there continuity between the (T830) Signal circuit and any other circuit?

      Yes 

      • Repair the (T830) Signal circuit for a short to another circuit.
      • Perform the TRANSMISSION VERIFICATION TEST. Refer to TRANSMISSION VERIFICATION TEST .

      No 

  7. CHECK THE (Z92) GROUND CIRCUIT FOR AN OPEN OR HIGH RESISTANCE 
    1. Turn the ignition off.
    2. Disconnect the TCM harness connector.
    3. Disconnect the Paddle Switch connector.
    4. Measure the resistance of the (Z92) Ground circuit.

      Is the resistance below 3.0 Ohms?

      Yes 

      • Go To  8

      No 

      • Repair the (Z92) Ground circuit for an open or high resistance.
      • Perform the TRANSMISSION VERIFICATION TEST. Refer to TRANSMISSION VERIFICATION TEST .
  8. REPLACE THE PADDLE SWITCH AND RETEST FOR DTC 
    1. Replace the Paddle switch.
    2. Connect the component and all harness connectors.
    3. Using the Environmental Data or When Monitored Conditions above, operate the vehicle within the conditions that set the DTC.
    4. With the scan tool, read DTCs.

      Did the DTC return?

      Yes 

      No