P1540
Schematic:
CIRCUIT DESCRIPTION
The A/C pressure sensor is a variable voltage transducer. The Powertrain Control module (PC) determines the pressure of the refrigerant system based on the voltage from the sensor. When the pressure is low, the sensor voltage is low. When the pressure is high, the sensor voltage is high. The PCM sends the A/C pressure to the DIM over the Class 2 data line. The DIM will not request A/C clutch engagement if the A/C pressure is high.
CONDITIONS FOR RUNNING THE DTC
The DIM must be powered.
CONDITIONS FOR SETTING THE DTC
The A/C refrigerant pressure is greater than 2968 kPa (430 psi) for more than 500 milliseconds.
ACTION TAKEN WHEN THE DTC SETS
The A/C clutch turns off.
CONDITIONS FOR CLEARING THE MIL/DTC
^ When the A/C refrigerant pressure drops to less than 1386 kPa (201 psi) the DIM will clear the current DTC and go to a history DTC. The history DTC will clear after 40 ignition cycles.
^ Use a scan tool in order to clear the MIL/DTC.
DIAGNOSTIC AIDS
^ If DTC P1540 is stored as a history code it indicates that the DIM did receive a high A/C refrigerant pressure message from the PCM. The code could have been caused by an intermittent short to voltage on the sensor signal circuit which would cause the PCM to set DTC P0530. The code could be the result of an actual A/C refrigerant over-pressure condition.
^ It is possible for the refrigerant system pressure to exceed 2968 kPa (430 psi) during extended engine idle speed with A/C on in very high ambient temperatures (greater than 110°F). This could be caused by:
^ an overcharged A/C system.
^ a failed A/C pressure sensor.
^ non-operating Cooling System fans.
^ blockage in a refrigerant line.
^ The following may cause an intermittent between the PCM and the A/C pressure sensor:
- A bent terminal
- A backed out terminal
- A damaged terminal
- Poor terminal tension
- A chafed wire
- A broken wire inside the insulation
^ When diagnosing for an intermittent short or an open, manipulate the A/C pressure sensor wire harness while watching the test equipment for changes.
TEST DESCRIPTION
