Diagnostic Test

CHECK FOR AN ACTIVE DTC
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.

NOTE:
If P0688-AUTO SHUTDOWN RELAY SENSE CIRCUIT LOW has set along with any of the O2 SENSOR HEATER CIRCUIT HIGH DTCs, all of the O2 Sensor Heater Control circuits need to be checked for a short to voltage.
1. Start the engine and allow it to idle for at least 60 seconds.
2. With the scan tool, read the active DTCs.
  Is the DTC active?
  
  Yes
  - Go To 2
  No
  - Perform the INTERMITTENT DTC diagnostic procedure. Refer to INTERMITTENT CONDITION .
O2 SENSOR 2/1 HEATER ELEMENT
1. Turn the ignition off.
  NOTE:
  Allow the O2 Sensor to cool down to room temperature.
2. Disconnect the 2/1 O2 Sensor harness connector.
3. Measure the resistance across the O2 Sensor 2/1 Heater element, between the O2 Sensor 2/1 Heater Control terminal and the Heater ground terminal at the component connector.
  NOTE:
  O2 Sensor 2/1 Heater Element resistance values should be measured at 21.1°C (70°F). The resistance value will vary with different temperature values.
  
  Is the O2 Sensor 2/1 Heater Element resistance between 2.0 and 30.0 Ohms?
  
  Yes
  - Go To 3
  No
  - Verify that there is good pin to terminal contact in the 2/1 O2 Sensor and Powertrain Control Module connectors. If OK, replace the O2 Sensor. Refer to SENSOR, OXYGEN, REMOVAL .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE (K199) O2 SENSOR 2/1 HEATER CONTROL CIRCUIT
1. Turn the ignition on.
2. Using a 12-volt test light connected to ground, probe the (K199) O2 Sensor 2/1 Heater Control circuit in the O2 Sensor harness connector.
  NOTE:
  Make sure the test light is probing the circuit before actuating the Heater Test or a DTC may set and not allow the actuation.
3. With the scan tool, actuate the O2 Heater Test with the Sensor harness connector still disconnected.
  NOTE:
  The test light should be illuminated and bright proportional to the maximum duty cycle allowed by the scan tool. For example, if the scan tool allows 100% actuation, the brightness should be as bright as a direct connection to the battery. If the scan tool allows a maximum 25% actuation, the brightness should be 25% as bright as a direct connection to the battery.
  
  Does the test light illuminate accordingly during the actuation?
  
  Yes
  - Go To 4
  No
  - Go To 5
CHECK THE O2 SENSOR 2/1 HEATER GROUND CIRCUIT FOR AN OPEN
1. Turn the ignition off.
2. Measure the resistance between an engine ground and the O2 Sensor 2/1 Heater ground circuit in the O2 Sensor harness connector.
  Is the resistance below 3.0 Ohms?
  
  Yes
  - Verify that there is good pin to terminal contact in the O2 Sensor 2/1 and Powertrain Control Module connectors. If OK, replace the O2 Sensor. Refer to SENSOR, OXYGEN, REMOVAL .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Repair the open in the O2 Sensor 2/1 Heater ground circuit.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE (K199) O2 SENSOR 2/1 HEATER CONTROL CIRCUIT FOR A SHORT TO VOLTAGE
1. Turn the ignition off.
2. Disconnect the PCM C2 harness connector.
3. Turn the ignition on.
4. Measure the voltage between ground and the (K199) O2 Sensor 2/1 Heater Control circuit at the O2 Sensor 2/1 harness connector.
  Is there any voltage present?
  
  Yes
  - Repair the short to voltage in the (K199) O2 Sensor 2/1 Heater Control circuit.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 6
CHECK THE (K199) O2 SENSOR 2/1 HEATER CONTROL CIRCUIT FOR AN OPEN
1. Turn the ignition off.
  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.
2. Connect the (special tool #10436, Adapter, GPEC Diagnostic).
3. Measure the resistance of the (K199) O2 Sensor 2/1 Heater Control circuit from the O2 Sensor harness connector to the GPEC Adaptor.
  Is the resistance below 3.0 Ohms?
  
  Yes
  - Go To 7
  No
  - Repair the open in the (K199) O2 Sensor 2/1 Heater Control circuit.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Oxygen Sensor 2/1 and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the Oxygen Sensor 2/1 and Powertrain Control Module connectors.
4. Perform any Service Bulletins that may apply.
  Were there any problems found?
  
  Yes
  - Repair as necessary.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Replace and program the Powertrain Control Module (PCM) in accordance with the Service Information. Refer to MODULE, POWERTRAIN CONTROL, REMOVAL .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .