Diagnostic Test

ECT SENSOR OPERATION
NOTE:
Diagnose and repair any other ECT Sensor or O2 Sensor DTCs that are present before continuing with this test procedure.

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.
3. Compare the ECT Sensor value with the IAT Sensor and AAT Sensor values.
  NOTE:
  If engine coolant temperature is above 82°C (180°F), allow the engine to cool until 65°C (150°F) is reached.
4. Start the engine and allow it to idle.
5. During engine warm-up, monitor the 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).
  Is the ECT Sensor value within a reasonable range with the other sensors at ignition on and 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 Engine Coolant Temperature Sensor and Powertrain Control Module connectors. If OK, replace the Engine Coolant Temperature Sensor.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK FOR AN ACTIVE DTC
1. With the scan tool, read DTCs and record on the repair order.
2. Test drive or operate the vehicle in accordance with the when monitored and set conditions.
  Is the DTC active or pending?
  
  Yes
  - Go To 3
  No
  - Perform the INTERMITTENT CONDITION diagnostic procedure. Refer to INTERMITTENT CONDITION .
CHECK THE FUEL DELIVERY SYSTEM
1. Perform the CHECKING THE FUEL DELIVERY SYSTEM test procedure. Refer to CHECKING THE FUEL DELIVERY SYSTEM (HARD START) .
  Were any problems found?
  
  Yes
  - Perform the appropriate repair.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 4
O2 SENSOR HEATER OPERATION
1. Turn the ignition off.
  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.
2. Turn the ignition on.
3. With the scan tool, actuate the O2 Sensor 1/1 Heater Test.
4. 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 and Powertrain Control Module connectors. If no problems are found, replace the O2 Sensor. Refer to SENSOR, OXYGEN, REMOVAL AND INSTALLATION .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 5
CHECK THE O2 SENSOR OPERATION
1. Start the engine.
2. With the scan tool, monitor the O2 Sensor 1/1 reading.
  NOTE:
  If one of the O2 Sensor Signal or Return circuit is shorted to ground the scan tool will display all O2 Sensor voltage readings low. The O2 Sensor that is shorted to ground will display a voltage reading near or at 0 volts.
  
  NOTE:
  If one of the O2 Sensor Signal or Return circuits are shorted to voltage, the scan tool will display all O2 Sensor voltage readings high.
  
  Is the voltage switching between 2.5 and 3.4 volts?
  
  Yes
  - Go To 8
  No
  - Go To 6
CHECK THE UPSTREAM O2 SENSOR RETURN CIRCUIT
1. Turn the ignition on, engine not running.
2. Disconnect the O2 Sensor 1/1 harness connector.
3. Measure the voltage on the (K902) O2 Sensor 1/1 Return circuit in the O2 Sensor harness connector.
  Is the voltage at 2.5 volts?
  
  Yes
  - Go To 7
  No
  - Check the (K902) O2 Sensor 1/1 Return circuit for a short to ground, open or short to voltage and repair if necessary. Inspect the O2 Sensor 1/1 connector and the PCM harness connector. If no problems are found, replace and program the Powertrain Control Module in accordance with the Service Information.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE O2 SENSOR 1/1 SIGNAL CIRCUIT
1. With the scan tool, monitor the O2 Sensor 1/1 voltage.
2. O2 Sensor voltage should read between 4.1 and 5.0 volts on the scan tool with the connector disconnected.
3. Connect a jumper between the (K41) O2 Sensor 1/1 Signal circuit and the (K902) O2 Sensor 1/1 Return circuit at the O2 Sensor 1/1 harness connector.
  NOTE:
  The voltage should drop from between 4.1 and 5.0 volts to 2.5 volts with the jumper in place.
  
  Did the O2 Sensor voltage change from between 4.1 and 5.0 volts to 2.5 volts with the jumper installed?
  
  Yes
  - Verify that there is good pin to terminal contact in the O2 Sensor and Powertrain Control Module connectors. If no problems are found, replace the O2 Sensor. Refer to SENSOR, OXYGEN, REMOVAL AND INSTALLATION .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Check the (K41) O2 Sensor 1/1 Signal circuit for a short to ground, open or short to voltage and repair if necessary. Inspect the O2 Sensor 1/1 connector and the PCM harness connector. If no problems are found: Go To 8
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
ENGINE 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 .
  No
  - Go To 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
  - Replace the Powertrain Control Module in accordance with the Service information. Refer to MODULE, POWERTRAIN CONTROL (PCM), REMOVAL AND INSTALLATION .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  - Test complete.