Circuit Description
The air conditioning (A/C) system uses an A/C refrigerant pressure sensor mounted in the high pressure side of the A/C refrigerant system to monitor A/C refrigerant pressure. The engine control module (ECM) uses this information to turn ON the engine coolant fans when the A/C refrigerant pressure is high and to keep the compressor disengaged when A/C refrigerant pressure is excessively high or low.
The air conditioning pressure (ACP) sensor operates like other 3-wire sensors. The ECM applies a 5-volt reference and a sensor ground to the sensor. Changes in the A/C refrigerant pressure will cause the ACP sensor input to the ECM to vary. The ECM monitors the ACP sensor signal circuit and can determine when the signal is outside of the possible range of the sensor. When the signal is out of range for a prolonged period of time, the ECM will not allow the A/C compressor clutch to engage. This is done to protect the compressor.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0533 Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit High Voltage
Conditions for Setting the DTC
| • | A/C pressure is greater than 4.95 percent of the sensor reading scale. |
| • | Engine is running. |
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Failure Records buffers. |
| • | A history DTC is stored. |
| • | The A/C compressor operation will be disabled while the high voltage indication exists. |
Conditions for Clearing the MIL/DTC
| • | A history DTC will clear after 40 consecutive warm-up cycles without a fault. |
| • | DTCs can be cleared by using the scan tool. |
| • | Disconnecting the ECM battery feed for more than 10 seconds. |
Diagnostic Aids
Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connection at the ECM.
Inspect the wiring harness for damage. If the harness appears to be OK, observe the A/C pressure display on the scan tool while moving the connectors and wiring harnesses related to the A/C pressure sensor. A change in the A/C pressure display will indicate the location of the fault.
If DTC P0533 cannot be duplicated, reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to set occurs. This may assist in diagnosing the condition.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: HVAC Schematics | ||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||
2 |
Does the scan tool display air conditioning pressure (ACP) sensor voltage below the specified value? | 0.06 V | Go to Step 3 | Go to Step 4 | ||||||
3 |
Does the ACP voltage read more than the specified value? | 4.9 V | Go to Step 5 | Go to Step 6 | ||||||
4 |
Does the scan tool display ACP voltage below the specified value? | 0.06 V | Go to Step 5 | Go to Diagnostic Aids | ||||||
5 | Inspect the ACP sensor harness connector terminals for the following conditions:
Is a problem found? | -- | Go to Step 8 | Go to Step 9 | ||||||
6 |
Does the test light illuminate? | -- | Go to Step 7 | Go to Step 11 | ||||||
7 | Check the ACP sensor 5-volt reference circuit for an open or short to voltage and repair as needed. Is the repair complete? | -- | Go to Step 13 | Go to Step 10 | ||||||
8 | Repair the connection terminals as necessary. Is the repair complete? | -- | Go to Step 13 | -- | ||||||
9 | Replace the ACP sensor. Is the repair complete? | -- | Go to Step 13 | -- | ||||||
10 | Replace the engine control module (ECM). Is the repair complete? | -- | Go to Step 13 | -- | ||||||
11 | Check the ACP sensor signal circuit for an open or short to voltage. Is a problem found? | -- | Go to Step 12 | Go to Step 10 | ||||||
12 | Repair the A/C pressure sensor signal circuit. Is the repair complete? | -- | Go to Step 13 | -- | ||||||
13 |
Does the scan tool indicate that this diagnostic has run and passed? | -- | Go to Step 14 | Go to Step 2 | ||||||
14 | Check if any additional DTCs are set. Are any DTCs displayed that have not been diagnosed? | -- | System OK | |||||||
