Diagnostic Fault Information
Circuit/System Description
The HVAC control module monitors the low side refrigerant pressure through the A/C refrigerant pressure sensor. The HVAC control module
supplies a 5-volt reference and a low reference to the sensor. Changes in the A/C refrigerant pressure cause the sensor signal to the HVAC control
module to vary. When the pressure is high, the signal voltage is high. When the pressure is low, the signal voltage is low. When pressure is high,
the HVAC control module sends a message to the ECM to turn on the cooling fans on. When pressure is too high or too low, the HVAC control
module will not allow the A/C compressor to operate.
Conditions for Running the DTC
* Engine is running.
* Any of the conditions for setting the DTC are met for 15 seconds.
Conditions for Setting the DTC
* The HVAC control module detects that the A/C pressure is less than 2.03 psi (14 kPa) sets DTC P2518 12.
* The HVAC control module detects that the A/C pressure is more than 101.5 psi (700 kPa) sets DTC P2518 11.
Action Taken When the DTC Sets
The A/C compressor is disabled.
Conditions for Clearing the DTC
* The history DTC will clear after 40 consecutive ignition cycles have occurred without a malfunction.
* The DTC will become history if the HVAC control module no longer detects a failure.
Diagnostic Aids
A malfunction within the refrigerant system causing high pressure can cause this DTC to set.
Reference Information
Schematic Reference
HVAC Schematics (See: Heating and Air Conditioning/Diagrams/Electrical Diagrams/HVAC - Automatic)
Connector End View Reference
Component Connector End Views (See: Diagrams/Connector Views)
Description and Operation
* Air Delivery Description and Operation (See: Heating and Air Conditioning/Description and Operation/HVAC - Automatic/Air Delivery
Description and Operation)
* Air Temperature Description and Operation (See: Heating and Air Conditioning/Description and Operation/HVAC - Automatic/Air
Temperature Description and Operation)
Electrical Information Reference
* Circuit Testing (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Circuit
Testing/Circuit Testing)
* Connector Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic
Procedures/Connector Repairs/Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (See: Testing and Inspection/Component Tests and General Diagnostics/General
Electrical Diagnostic Procedures/Circuit Testing/Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Wiring
Repairs/Wiring Repairs)
Scan Tool Reference
Control Module References (See: Testing and Inspection/Programming and Relearning) for scan tool information
Circuit/System Verification
