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
Management/Computers and Control Systems/Oxygen Sensor/Service and Repair)
* Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 (1500 Series) (See: Powertrain Management/Computers and Control
Systems/Oxygen Sensor/Service and Repair)Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 (2500 Series) (See: Powertrain
Management/Computers and Control Systems/Oxygen Sensor/Service and Repair)
* Control Module References (See: Testing and Inspection/Programming and Relearning) for ECM replacement, setup, and programming
P2518
DTC P2518
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category.
DTC Descriptors
DTC P2518 11
- A/C Refrigerant Low Side Fluid Pressure Sensor Circuit Above Maximum Threshold
DTC P2518 12
- A/C Refrigerant Low Side Fluid Pressure Sensor Circuit Below Minimum Threshold
