Diagnostic Test

O2 SENSOR BELOW 2.52 VOLTS
1. Start the engine.
2. Allow the engine to reach normal operating temperature.
3. With a scan tool, read the 2/2 O2 Sensor voltage.
  Is the voltage below 2.52 volts?
  
  Yes
  - Go to step 2
  No
  - Refer to the INTERMITTENT CONDITION Diagnostic Procedure. See DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure .
(K243) O2 2/2 SIGNAL CIRCUIT
1. Turn the ignition off.
2. Disconnect the 2/2 O2 Sensor harness connector.
3. Ignition on, engine not running.
4. With a scan tool, monitor the 2/2 O2 Sensor voltage.
  Is the O2 Sensor voltage above 4.8 volts?
  
  Yes
  - Go to step 3
  No
  - Go to step 5
O2 SENSOR

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1. Measure the voltage on the (K908) O2 Return Downstream circuit in the O2 Sensor harness connector.
  Is the voltage at 2.5 volts?
  
  Yes
  - Replace the O2 Sensor.
  - Perform the PCM Verification Test. See DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure
  No
  - Go to step 4
(K908) O2 RETURN DOWNSTREAM CIRCUIT SHORTED TO GROUND

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1. Turn the ignition off.
2. Disconnect the C12 PCM harness connector.
3. Measure the resistance between ground and the (K908) O2 Return Downstream circuit in the O2 Sensor harness connector.
  Is the resistance below 100 ohms?
  
  Yes
  - Repair the short to ground in the (K908) O2 Return Downstream circuit.
  - Perform the PCM Verification Test. See DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure
  No
  - Go to step 7
(K243) O2 2/2 SIGNAL CIRCUIT SHORTED TO GROUND

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1. Turn the ignition off.
2. Disconnect the C1 PCM harness connector.
3. Measure the resistance between ground and the (K243) O2 2/2 Signal circuit in the O2 Sensor harness connector.
  Is the resistance below 100 ohms?
  
  Yes
  - Repair the short to ground in the (K243) O2 2/2 Signal circuit.
  - Perform the PCM Verification Test. See DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure
  No
  - Go to step 6
(K243) O2 2/2 SIGNAL CIRCUIT SHORTED TO THE (K908) O2 RETURN DOWNSTREAM CIRCUIT

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1. Measure the resistance between the (K243) O2 2/2 Signal circuit and the (K908) O2 Return Downstream circuit in the O2 Sensor harness connector.
  Is the resistance below 100 ohms?
  
  Yes
  - Repair the short between the (K908) O2 Return Downstream circuit and the (K243) O2 2/2 Signal circuit.
  - Perform the PCM Verification Test. See DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure
  No
  - Go to step 7
PCM
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.
1. Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.
  Were there any problems found?
  
  Yes
  - Repair as necessary.
  - Perform the PCM Verification Test. See DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure
  No
  - Replace and program the Powertrain Control Module per Service Information. See DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure
  - Perform the PCM Verification Test. See DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure