Diagnostic Test

WARNING: This page is about a different car, the 2024 Jeep Grand Cherokee L. However, it is still accessible from the selected car via links, so may be relevant.

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 2
  No
  - Perform the INTERMITTENT CONDITION diagnostic procedure. Refer to INTERMITTENT CONDITION .
CHECK FOR OTHER DTCS
1. Refer to the recorded DTCs.
  Are there any 5-Volt reference DTCs active or pending?
  
  Yes
  - Perform the applicable diagnostic procedure(s). Refer to DIAGNOSTIC CODE INDEX, 5.7L .
  No
  - Go To 3
CHECK THE (F856) 5-VOLT SUPPLY CIRCUIT FOR PROPER VOLTAGE AT THE MAP SENSOR HARNESS CONNECTOR
1. Turn the ignition off.
2. Disconnect the harness connector at the component of the circuit being tested. Note: The ECU harness connector should still be connected during this test step.
3. Turn the ignition on.
4. Set the DVOM to measure DC voltage.
5. Connect the negative lead of the DVOM to a known good ground.
6. With the positive lead of the DVOM, measure the voltage of the circuit being tested at the component harness connector.
7. If it is necessary to probe a terminal at a PCM harness connector, connect the (special tool #10436, Adapter, GPEC Diagnostic)
  NOTE:
  The GPEC Diagnostic Adaptor can add up to 1.5 Ohms of resistance to the circuit.
  
  NOTE:
  Normal operating voltage should be between 4.8 and 5.2 volts.
  
  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.
  
  Does the circuit have the proper voltage present?
  
  Yes
  - Verify that there is good pin to terminal contact in the MAP Sensor and Powertrain Control Module connectors. If no problems are found, replace the MAP Sensor in accordance with the Service Information. Refer to MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Repair the (F856) 5-Volt Supply circuit for an open or high resistance.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .