Diagnostic Test

WARNING: This page is about a different car, the 2017 Jeep Cherokee. However, it is still accessible from the selected car via links, so may be relevant.

CHECK THE ECT SENSOR OPERATION
NOTE:
For this test to be valid, the thermostat must be operating correctly.

NOTE:
This test works best if performed on a cold engine (cold soak).
1. Turn the ignition on.
2. With the scan tool, read the Engine Coolant Temperature (ECT) Sensor value. If the engine was allowed to sit overnight (cold soak), the temperature value should be a sensible value that is somewhere close to the ambient temperature.
  NOTE:
  If engine coolant temperature is above 82°C (180°F), allow the engine to cool until 65°C (150°F) is reached.
3. Start the Engine.
4. During engine warm-up, monitor the Engine Coolant Temperature (ECT) Sensor value. The temperature value change should be a smooth transition from start up to normal operating temperature 82°C (180°F). The value should reach at least 82°C (180°F).
  Did the ECT value increase smoothly and did it reach at least 82°C (180°F)?
  
  Yes
  - Go To 2
  No
  - Verify that there is good pin to terminal contact in the ECT Sensor and Powertrain Control Module connectors. If OK, replace the Engine Coolant Temperature Sensor. Refer to SENSOR, COOLANT TEMPERATURE, REMOVAL, 2.4L .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .
CHECK FOR AN ACTIVE DTC
1. Diagnose all other DTCs before continuing.
2. Start the engine.
3. Allow the engine to reach normal operating temperature.
4. With the scan tool, read DTCs and record on the repair order.
  NOTE:
  It may be necessary to drive the vehicle to meet the conditions to set this DTC, try to repeat the conditions in which the fault originally set by reviewing the Freeze Frame data.
  
  Is the DTC active or pending?
  
  Yes
  - Go To 3
  No
  - Perform the INTERMITTENT CONDITION diagnostic procedure. Refer to INTERMITTENT CONDITION .
CHECK THE O2 SENSOR 1/1 VOLTAGE READINGS
NOTE:
This DTC will set due to poor engine performance as well as a faulty O2 Sensor. If the vehicle exhibits any fuel system or driveability issues, or has any other driveability DTCs present, repair those concerns before proceeding with this test.
1. Start the engine and allow it to idle.
  NOTE:
  If the Powertrain Control Module detects an active open or short on any of the O2 Sensor 1/1 circuits, it will power down all of the O2 Sensor circuits to protect the O2 Sensor PCM internal Application-Specific Integrated Circuit (ASIC) from being damaged.
2. Carefully back-probe the O2 Sensor 1/1 harness connector and measure the voltage at the (K41) O2 Sensor Signal circuit and the (K902) O2 Sensor Return circuit to ground.
  NOTE:
  The (K902) O2 Sensor 1/1 Return circuit voltage should read approximately 3.8 volts and the (K41) O2 Sensor 1/1 Signal circuit should read between approximately 3.35 volts and 4.25 volts if operating normally with no opens or shorts.
  
  Do the circuit voltages read as described?
  
  Yes
  - Perform the INTERMITTENT CONDITION diagnostic procedure. Refer to INTERMITTENT CONDITION .
  No
  - Go To 4
CHECK THE O2 SENSOR 1/1 CIRCUITS FOR A SHORT TO VOLTAGE
1. Turn the ignition off.
2. Disconnect the O2 Sensor 1/1 harness connector.
3. Turn the ignition on.
4. Measure for voltage at the:
  - (K41) O2 Sensor 1/1 Signal circuit at the O2 Sensor 1/1 harness connector.
  - (K902) O2 Sensor 1/1 Return circuit at the O2 Sensor 1/1 harness connector.
  - (K89) O2 Sensor 1/1 Current Pump circuit at the O2 Sensor 1/1 harness connector.
  Do any of the circuits measure above 0.5 volts?
  
  Yes
  - Repair the circuit that measured above 0.5 volts for a short to voltage.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .
  No
  - Go To 5
CHECK THE O2 SENSOR 1/1 CIRCUITS FOR A SHORT TO GROUND
1. Turn the ignition off.
2. Disconnect the PCM C2 harness connector.
3. Check for continuity between ground and the:
  - (K41) O2 Sensor 1/1 Signal circuit at the O2 Sensor 1/1 harness connector.
  - (K902) O2 Sensor 1/1 Return circuit at the O2 Sensor 1/1 harness connector.
  - (K89) O2 Sensor 1/1 Current Pump circuit at the O2 Sensor 1/1 harness connector.
  - (K79) O2 Sensor 1/1 Heater Control circuit at the O2 Sensor 1/1 harness connector.
  Is there continuity between ground and any of the above circuits?
  
  Yes
  - Repair the circuit(s) that shows continuity for a short to ground.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .
  No
  - Go To 6
CHECK THE O2 SENSOR 1/1 CIRCUITS FOR AN OPEN OR HIGH RESISTANCE
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. Connect the (special tool #10436, Adapter, GPEC Diagnostic).
2. Measure the resistance of the:
  - (K41) O2 Sensor 1/1 Signal circuit between the O2 Sensor 1/1 harness connector and the GPEC Adaptor.
  - (K902) O2 Sensor 1/1 Return circuit between the O2 Sensor 1/1 harness connector and the GPEC Adaptor.
  - (K89) O2 Sensor 1/1 Current Pump circuit between the O2 Sensor 1/1 harness connector and the GPEC Adaptor.
  - (K79) O2 Sensor 1/1 Heater Control circuit between the O2 Sensor 1/1 harness connector and the GPEC Adaptor.
  Is the resistance below 3.0 Ohms for each of the above circuits?
  
  Yes
  - Go To 7
  No
  - Repair the circuit that measured above 3.0 Ohms for an open or high resistance.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .
CHECK THE FUEL PRESSURE READING
WARNING:
The fuel system is under a constant pressure (even with the engine off). Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released. Failure to follow these instructions can result in possible serious or fatal injury.
1. Turn the ignition off.
2. Install Fuel Pressure Decay Tester (special tool #8978A, Decay Tool, Fuel) to the fuel rail.
3. Turn the ignition on.
4. With the scan tool, actuate the Fuel System test and observe the fuel pressure gauge.
  NOTE:
  Fuel pressure specification: 400 kPa +/- 14 kPa (58 psi +/- 2 psi).
5. Turn the ignition off.
  Choose a conclusion that best matches your fuel pressure reading.
  
  Within Specification
  - Go To 8
  Above Specification
  - Replace the fuel filter/pressure regulator. Refer to MODULE, FUEL PUMP, REMOVAL .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .
  Below Specification
  - Go To 13
CHECK THE O2 SENSOR 1/1 HEATER OPERATION
1. Turn the ignition off.
2. Reconnect the PCM C2 harness connector and the O2 Sensor 1/1 harness connector.
  NOTE:
  Wait a minimum of 10 minutes to allow the O2 Sensor to cool down before continuing the test. Allow the O2 Sensor voltage to stabilize at 5.0 volts.
3. Turn the ignition on.
4. With the scan tool, actuate the O2 Heater 1/1 Test.
5. With the scan tool, monitor O2 Sensor 1/1 voltage for at least two minutes.
  Does the voltage stay above 4.5 volts?
  
  Yes
  - Verify that there is good pin to terminal contact in the O2 Sensor 1/1 and Powertrain Control Module connectors. If OK, replace the O2 Sensor. Refer to SENSOR, OXYGEN, REMOVAL, 2.4L .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .
  No
  - Go To 9
CHECK THE MAP SENSOR OPERATION
1. Turn the ignition off.
2. Connect a Vacuum Gauge to a Manifold Vacuum source.
3. Start the engine.
4. Allow the engine to idle.
  NOTE:
  If engine will not idle, maintain a constant RPM above idle.
5. With the scan tool, read the MAP Sensor vacuum value.
  Is the scan tool reading within 1" of Hg on the Vacuum Gauge reading?
  
  Yes
  - Go To 10
  No
  - Verify that there is good pin to terminal contact in the MAP Sensor and Powertrain Control Module connectors. If OK, replace the MAP Sensor. Refer to SENSOR, MANIFOLD AIR PRESSURE (MAP), REMOVAL .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .
CHECK THE ENGINE FOR A MECHANICAL PROBLEM
1. Turn the ignition off.
2. Check for any of the following conditions/mechanical problems:
  - AIR INDUCTION SYSTEM - must be free from leaks.
  - ENGINE VACUUM - must be at least 13 inches in neutral
  - ENGINE VALVE TIMING - must be within specifications
  - ENGINE COMPRESSION - must be within specifications
  - ENGINE EXHAUST SYSTEM - must be free of any restrictions or leaks.
  - ENGINE PCV SYSTEM - must flow freely
  - TORQUE CONVERTER STALL SPEED - must be within specifications
  - POWER BRAKE BOOSTER - no internal vacuum leaks
  - FUEL - must be free of contamination
  - FUEL INJECTOR - plugged or restricted injector; control wire not connected to correct injector
  Are there any engine mechanical problems?
  
  Yes
  - Repair as necessary.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .
  No
  - Go To 11
REPLACE THE O2 SENSOR 1/1 AND RETEST FOR DTCS
1. Replace the O2 Sensor 1/1 in accordance with the Service Information. Refer to SENSOR, OXYGEN, REMOVAL, 2.4L .
2. Reconnect the O2 Sensor 1/1 Sensor and PCM harness connectors.
3. Turn the ignition on.
4. With the scan tool, erase DTCs.
5. Using the Freeze Frame Data or When Monitored Conditions above, operate the vehicle within the conditions that set the DTC.
6. With the scan tool, read DTCs.
  Did the DTC return?
  
  Yes
  - Go To 12
  No
  - Replacing the O2 Sensor 1/1 repaired the fault.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .
CHECK RELATED HARNESS CONNECTIONS
1. Disconnect all PCM harness connectors.
2. Disconnect all related in-line harness connections (if equipped).
3. Disconnect the related component harness connectors.
4. 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.
5. Connect all PCM harness connectors. Be certain that all harness connectors are fully seated and the connector locks are fully engaged.
6. Connect all in-line harness connectors (if equipped). Be certain that all connectors are fully seated and the connector locks are fully engaged.
7. Connect all related component harness connectors. Be certain that all connectors are fully seated and the connector locks are fully engaged.
8. With the scan tool, erase DTCs.
9. Test drive or operate the vehicle in accordance with the when monitored and set conditions.
10. With the scan tool, read DTCs.
  Did the DTC return?
  
  Yes
  - Replace and program the Powertrain Control Module (PCM) in accordance with the Service Information. Refer to MODULE, POWERTRAIN CONTROL (PCM), REMOVAL, 2.4L/3.2L .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .
  No
  - The wiring or poor connection problem has been repaired.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .
CHECK THE FUEL SUPPLY LINE FOR A RESTRICTION
WARNING:
The fuel system is under a constant pressure (even with the engine off). Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released. Failure to follow these instructions can result in possible serious or fatal injury.
1. Turn the ignition off.
2. Raise vehicle on hoist and disconnect the fuel pressure line at the fuel pump module.
3. Install Fuel Pressure Decay Tester (special tool #8978A, Decay Tool, Fuel) between the fuel supply line and the fuel pump module.
4. Turn the ignition on.
5. With the scan tool, actuate the ASD Fuel System test and observe the fuel pressure gauge.
  NOTE:
  Fuel pressure specification: 400 kPa +/- 14 kPa (58 psi +/- 2 psi).
  
  Is the fuel pressure within specification?
  
  Yes
  - Repair or replace fuel supply line as necessary.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .
  No
  - Go To 14
CHECK THE FUEL PUMP INLET STRAINER FOR BLOCKAGE
WARNING:
The fuel system is under a constant pressure (even with the engine off). Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released.
1. Turn the ignition off.
2. Remove the Fuel Pump Module and inspect the Fuel Inlet Strainer.
  Is the Fuel Inlet Strainer plugged?
  
  Yes
  - Replace the Fuel Pump Inlet Strainer. Refer to MODULE, FUEL PUMP, REMOVAL .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .
  No
  - Verify that there is good pin to terminal contact in the Fuel Pump Module, Relay and Powertrain Control Module connectors. If OK, replace the Fuel Pump Module. Refer to MODULE, FUEL PUMP, REMOVAL .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .