1. Ignition ON, observe the DTC information with a scan tool. Verify that no B52 HO2S heater DTCs are set.
锟斤拷If any B52 HO2S heater DTCs are set, perform those diagnostics first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle (See:
Diagnostic Trouble Code Descriptions/Diagnostic Trouble Code (DTC) List - Vehicle).
2. Engine idling, move the appropriate B52 HO2S 2 harness connector and the engine control module (ECM) harness connector while
monitoring the B52 HO2S 2 voltage parameter with a scan tool. Verify that the B52 HO2S parameter does not change abruptly while moving
the related harnesses.
锟斤拷If the B52 HO2S parameter does change abruptly while moving the related harnesses repair the circuit as necessary.
3. Engine idling at operating temperature, observe the appropriate B52 HO2S 2 parameter with a scan tool. Verify the following:
* The B52 HO2S 1 value should vary from below 200 mV to above 800 mV and respond to fueling changes.
* The B52 HO2S 2 should fluctuate at less than 380 mV or greater than 520 mV. The values should not remain within 380 mV and 520
mV.
4. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the
conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
Note: All modules must be powered down or misdiagnosis may result.
1. Ignition OFF, disconnect the harness connector at the appropriate B52 HO2S.
2. Ignition OFF, all vehicle systems OFF, this may take up to 2 minutes, test for less than 5 ohm between the low reference circuit terminal A
and ground.
锟斤拷If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
3. Ignition ON, verify the appropriate scan tool B52 HO2S parameter is approximately 450 mV.
锟斤拷If less than the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the K20 ECM.
锟斤拷If greater than the specified value, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.
4. Ignition ON, install a 3 A fused jumper wire between the signal circuit terminal B and ground. Verify the scan tool B52 HO2S parameter is
less than 60 mV.
锟斤拷If greater than the specified range, test the signal circuit for an open/high resistance. If the circuits test normal, replace the K20 ECM.
5. Verify none of the following conditions exist:
* Rich fuel injectors-Refer to Fuel Injector Diagnosis (CH47976) (See: Powertrain Management/Fuel Delivery and Air Induction/Fuel
Injector/Testing and Inspection)Fuel Injector Diagnosis (J39021 or Scan Tool) (See: Powertrain Management/Fuel Delivery and Air
Induction/Fuel Injector/Testing and Inspection)
* Water intrusion in the B52 HO2S harness connector
* High fuel system pressure-Refer to Fuel System Diagnosis (w/o FPCM) (See: Powertrain Management/Computers and Control
Systems/Testing and Inspection/Component Tests and General Diagnostics)Fuel System Diagnosis (FPCM) (See: Powertrain
Management/Computers and Control Systems/Testing and Inspection/Component Tests and General Diagnostics)
* Fuel that is contaminated-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) (See: Powertrain
Management/Computers and Control Systems/Testing and Inspection/Component Tests and General
Diagnostics/Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool))Alcohol/Contaminants-in-Fuel Diagnosis (Special Tool) (
See: Powertrain Management/Fuel Delivery and Air Induction/Fuel/Testing and Inspection/Alcohol/Contaminants-in-Fuel Diagnosis
(Special Tool))
* Fuel saturation of the evaporative emission (EVAP) canister
锟斤拷If you find any of the above conditions, repair as necessary.
6. If all circuits test normal, replace the appropriate B52 HO2S.
Repair Instructions
Caution: Refer to Heated Oxygen Sensor Resistance Learn Reset Caution (See: Powertrain Management/Computers and Control
Systems/Oxygen Sensor/Service Precautions/Heated Oxygen Sensor Resistance Learn Reset Caution).
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 (1500 Series) (See: Powertrain Management/Computers and Control
Systems/Oxygen Sensor/Service and Repair)Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 (2500 Series) (See: Powertrain
