The ECM(Engine Control Module) receives pressure signal in the A/C refrigerant high pressure side from the A/C refrigerant pressure sensor. This input indicates how much load the A/C compressor is putting on the engine and is one of the factors used by the ECM in order to determine the idle air control position for the idle speed. The circuits consist of a 5V reference and a ground, both provided by the ECM, and a signal from the sensor. The signal is a voltage which is proportional to the A/C pressure from 0 to 5V. Low pressure produces a low voltage signal and high pressure a high-voltage signal.
Checking output signals from A/C pressure sensor under detecting condition, if an signal above 4.65V lasts for more than 10 sec., ECM sets P0533.
Item | Detecting Condition | Possible cause |
DTC Strategy |
•
Detects sensor signal short to high voltage | 1. Poor connection 2. Short in signal circuit 3. Open in ground circuit 4. Faulty A/C Pressure sensor 5. Faulty ECM |
Enable Conditions |
•
Engine works | |
Threshold value |
•
Sensor output voltage > 4.65V | |
Diagnosis Time |
•
Continuous (More than 10 seconds failure for every 20 seconds test ) | |
MIL On Condition |
•
DTC only (NO MIL ON) |
Pressure(psi) | 101.4 | 391.6 | 17.25.3 | 3035.5 | 3208.1 |
Voltage(V) | 0.5 | 0.87 | 2.57 | 4.24 | 4.46 |
Fig.1) Normal waveforms of A/C pressure sensor during the time from turning on A/C switch to turning off A/C switch.
Fig.2) Normal data of A/C pressure sensor without A/C switch ON.
Fig.3) Abnormal data of A/C pressure sensor when A/C pressure sensor circuit open.
