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Home >> Jeep >> 2021 >> Grand Cherokee L Laredo, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 17 (5.7L - DTCS P0456 To P0629) >> DTC Troubleshooting >> P050B-Cold Start Ignition Timing Performance >> Diagnostic Test

Diagnostic Test

WARNING: This page is about a different variant/trim than selected.
  1. CHECK FOR AN ACTIVE DTC 
    NOTE:

    Low battery voltage can cause excessive current draw in very hot and very cold ambient temperatures. Look closely at the temperatures at which this DTC set and make sure the battery can pass a load test before continuing.

    1. Turn the ignition on.
    2. With the scan tool, read DTCs and review the DTC environmental information.

      Is the good trip counter greater than 0?

      Yes 

      No 

      • Go To  2
  2. CHECK FOR OTHER DTCS 
    1. Refer to the recorded DTCs.

      Are there any other PCM DTCs active or pending?

      Yes 

      No 

      • Go To  3
  3. CHECK THE THROTTLE PLATE FOR CONTAMINATION 
    1. Turn the ignition off.
    2. Remove the air cleaner assembly.
    3. Check for any signs of a foreign material (ice, dirt, or excessive carbon build up) on the throttle plate or in the bore causing the throttle plate to stick.

      Were any problems found?

      Yes 

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

      No 

      • Go To  4
  4. CHECK THE AIR INTAKE SYSTEM FOR A DIRTY AIR FILTER 
    1. Remove and inspect the air filter.

      Were any problems found?

      Yes 

      No 

      • Go To  5
  5. CHECK THE FUEL SYSTEM FOR CONTAMINATED FUEL 
    1. Inspect the fuel for contamination. (dirt, water, or other foreign material)

      Were any problems found?

      Yes 

      • Drain the fuel from the fuel tank into an approved gas holding tank and add clean fuel. Refer to DRAINING FUEL TANK .

      No 

      • Go To  6
  6. CHECK THE ETC (K447) MOTOR (+) CIRCUIT FOR EXCESSIVE RESISTANCE 
    1. Turn the ignition off.
    2. Disconnect the PCM C2 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. 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.

    4. Using a voltmeter, perform a voltage drop test by back probing the ETC (K447) Motor (+) circuit at the Throttle Body harness connector and the GPEC Adaptor. Make sure the voltmeter leads are connected so that positive polarity is displayed on the voltmeter.
      WARNING:

      When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in possible serious or fatal injury.

    5. Start the engine.

      Is the voltage below 0.2 volts?

      Yes 

      • Go To  7

      No 

  7. CHECK THE ETC (K448) MOTOR (-) CIRCUIT FOR EXCESSIVE RESISTANCE 
    1. Turn the ignition off.
    2. Move the Voltmeter leads to back probe the ETC (K448) Negative circuit at the Throttle Body harness connector and the GPEC Adaptor. Make sure the Voltmeter leads are connected so a positive polarity is displayed on the Voltmeter.
      WARNING:

      When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.

    3. Start the engine.

      Is the voltage below 0.2 volt?

      Yes 

      • Go To  8

      No 

  8. CHECK THE THROTTLE BODY FOR PROPER OPERATION 
    1. Turn the ignition off.
    2. Disconnect the C2 PCM harness connector.
    3. Measure the resistance of the ETC Motor by probing the GPEC Adaptor at the ETC (K447) Motor (+) circuit and the ETC (K448) Motor (-) circuit.

      Is the resistance between 2.5 and 25 Ohms at closed throttle?

      Yes 

      • Go To  9

      No 

      • Verify that there is good pin to terminal contact in the Throttle Body and Powertrain Control Module connectors. Replace the Throttle Body Assembly if no problems were found in the connectors. Disconnect the Battery when replacing the Throttle Body Assembly. After installation is complete, use a scan tool and select the ETC RELEARN function. Refer to THROTTLE BODY, REMOVAL AND INSTALLATION .
      • Perform the PCM VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  9. 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