Circuit Description
The powertrain control module (PCM) monitors the high side refrigerant pressure via the A/C refrigerant pressure sensor. The PCM applies a 5.0-volt reference and a low reference to the sensor. Changes in the A/C refrigerant pressure cause the A/C refrigerant pressure input to the PCM to vary. When the pressure is high, the signal voltage is high. When the pressure is low, the signal voltage is low. When the pressure is high the PCM commands the cooling fans on. When the pressure is too high or low the PCM will not allow the A/C compressor clutch to engage. When the DTC is set, the PCM does not allow the A/C compressor clutch to engage. This is done to protect the compressor. The PCM also sends the A/C pressure data to the Dash Integration Module (DIM) over the class 2 communication line. The DIM will not request A/C compressor clutch engagement and set DTC P1540 if the A/C pressure is too high.
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
| • | A/C pressure of less than 0.1 Volts |
| • | A/C pressure of greater than 4.92 Volts |
| • | The condition must be present for more than 20 seconds |
Action Taken When the DTC Sets
| • | The PCM stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records. |
Conditions for Clearing the DTC
| • | A History DTC will clear after forty consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. |
| • | The current DTC will clear when the diagnostic runs and does not fail. |
| • | The DTC can be cleared by using a scan tool. |
Diagnostic Aids
Important: Be sure to inspect PCM engine grounds for being secure and clean.
If DTC P0530 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.
If the problem is intermittent, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Tests for the proper operation of the circuit in the low voltage range.
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Tests for the proper operation of the circuit in the high voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to ground.
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Tests for a short to voltage in the 5 volt reference circuit.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: HVAC Schematics | ||||
1 | Did you perform the HVAC Diagnostic System Check? | -- | Go to Step 2 | |
2 |
Important: The ambient air temperature must be above 3 degrees Celsius (38 degrees Fahrenheit).
Does the A/C compressor operate | -- | Go to Step 3 | |
3 |
Does the scan tool indicate that the A/C High Side Pressure parameter is within the specified range? | 0.1-4.9 V | Go to Diagnostic Aids | Go to Step 4 |
Does the scan tool indicate that the A/C High Side Pressure parameter is less than the specified value? | 0.1 V | Go to Step 5 | Go to Step 11 | |
Does the scan tool indicate that the A/C High Side Pressure parameter is greater than the specified value? | 4.9 V | Go to Step 6 | Go to Step 9 | |
Does the voltage measure less than the specified value? | 5.0 V | Go to Step 7 | Go to Step 8 | |
7 |
Does the resistance measure less than the specified value? | 5 ohms | Go to Step 13 | Go to Step 12 |
8 | Test the 5 volt reference circuit of the A/C refrigerant pressure sensor for short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 14 |
9 | Test the 5 volt reference circuit of the A/C refrigerant pressure sensor for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 10 |
10 | Test the A/C refrigerant pressure sensor signal circuit of the A/C refrigerant pressure sensor for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 14 |
11 | Test the A/C refrigerant pressure sensor signal circuit of the A/C refrigerant pressure sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 14 |
12 |
Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 14 |
13 | Inspect for poor connections at the harness connector of the A/C refrigerant pressure sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 15 |
14 | Inspect for poor connections at the harness connector of the powertrain control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 16 |
15 | Replace the A/C refrigerant pressure sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in Heating, Ventilation and Air Conditioning. Did you complete the replacement? | -- | Go to Step 17 | -- |
16 |
Important: : Perform the programming procedure for the PCM. Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls - 3.5L. Did you complete the replacement? | -- | Go to Step 17 | -- |
17 |
Does the DTC reset? | -- | Go to Step 3 | System OK |
