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Home >> Jeep >> 2021 >> Grand Cherokee L Laredo, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 14 (5.7L - DTCS B1F08 To P0131) >> DTC Troubleshooting >> P0121-Throttle Position Sensor 1 Performance >> Diagnostic Test

Diagnostic Test

WARNING: This page is about a different variant/trim than selected.
  1. READ AND RECORD DTCS AND ENVIRONMENTAL DATA - ERASE DTCS AND CHECK FOR THE DTC TO RETURN 
    1. With the scan tool, read DTCs in all Electronic Control Units (ECUs) and record on the repair order.
    2. For future reference, with the scan tool, run and save a vehicle Scan Report and all related recorded data.
    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 When Monitored and Set Conditions above and recorded data, operate the vehicle in the conditions that set the DTC.
    7. With the scan tool, read DTCs.

    Did the DTC return?

    Yes 

    • Go To  3

    No 

    • Go To  2
  2. PERFORM THE THROTTLE FOLLOWER TEST 
    1. Turn the ignition on.
    2. With the scan tool, perform the ETC Throttle Follower Test and monitor the TPS 1 or TPS 2 voltage.
    3. Slowly press the accelerator pedal down.
      NOTE:

      The voltage for TPS 1 should start at approximately 0.7 volts and increase to approximately 4.3 volts.

      Is the TPS 1 voltage within the range of the listed specification?

      Yes 

      No 

      • Go To  3
  3. CHECK FOR OTHER DTCS 
    1. Refer to the recorded DTCs.

      Are there any system voltage or 5-Volt Reference DTCs active or pending?

      Yes 

      No 

      • Go To  4
  4. ISOLATE AND CHECK THE TPS (K22) POSITION SIGNAL 1 CIRCUIT FOR AN OPEN/HIGH RESISTANCE 
    1. The ignition must be off when checking the continuity of a circuit.
    2. Isolate the circuit by disconnecting the Electronic Control Unit (ECU) and the component harness connector containing the circuit being tested. Note:  Use the wiring diagram as a guide to follow the path of the circuit.
    3. Before measuring the resistance of any circuit, first measure the resistance between the two leads of the DVOM. Note:  The meter leads can add resistance to the measurement value.
    4. Connect one lead of the DVOM to the circuit being tested at the component harness connector.
    5. Connect the other lead to the circuit being tested at the GPEC Adaptor and measure the resistance of the circuit.
    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.

    1. If it is necessary to probe a terminal at a PCM harness connector, connect the (special tool #10436, Adapter, GPEC Diagnostic) to the appropriate PCM harness connector.
      NOTE:

      The GPEC Diagnostic Adaptor can add up to 1.5 Ohms of resistance to the circuit.

      Is the resistance below 3.0 Ohms?

      Yes 

      • Go To  5

      No 

  5. CHECK THE ABILITY OF THE PCM TO READ THE TPS POSITION SIGNAL 1 
    1. Reconnect the PCM C2 harness connector.
    2. Turn the ignition on.
    3. With the scan tool, monitor the TPS 1 voltage.
    4. Connect a jumper between the TPS (K22) Position Signal 1 circuit and the TPS (K922) Sensor Return circuit.
      NOTE:

      The TPS 1 voltage should change from approximately 5.0 volts with the connector unplugged to 0.0 volts with the jumper in place.

      Is the voltage reading within the listed specification when the jumper is installed?

      Yes 

      • Verify that there is good pin to terminal contact in the Throttle Body and Powertrain Control Module connectors. If no problems are found, replace the Throttle Body Assembly. Refer to THROTTLE BODY, REMOVAL AND INSTALLATION . Disconnect the Battery when replacing the Throttle Body Assembly. After installation is complete, use a scan tool and select the ETC RELEARN function.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  6
        NOTE:

        Remove the jumper before continuing.

  6. CHECK RELATED PCM AND COMPONENT CONNECTIONS 
    1. Perform any Service Bulletins that apply.
    2. Disconnect all PCM harness connectors.
    3. Disconnect all related in-line harness connections (if equipped).
    4. Disconnect the related component harness connectors.
    5. Inspect harness connectors, component connectors, and all male and female terminals for the following conditions:
      • Proper connector installation.
      • Damaged connector locks.
      • Corrosion.
      • Other signs of water intrusion.
      • Weather seal damage (if equipped).
      • Bent terminals.
      • Overheating due to a poor connection (terminal may be discolored due to excessive current draw).
      • Terminals that have been pushed back into the connector cavity.
      • Check for spread terminals and verify proper terminal tension.

      Repair any conditions that are found.

    6. Reconnect all PCM harness connectors. Be certain that all harness connectors are fully seated and the connector locks are fully engaged.
    7. Reconnect all in-line harness connectors (if equipped). Be certain that all connectors are fully seated and the connector locks are fully engaged.
    8. Reconnect all related component harness connectors. Be certain that all connectors are fully seated and the connector locks are fully engaged.
    9. With the scan tool, erase DTCs.
    10. Test drive or operate the vehicle in accordance with the when monitored and set conditions.
    11. With the scan tool, read DTCs.

      Did the DTC return?

      Yes 

      No