Code No. P0532: A/C Pressure Sensor Circuit Low Input

OPERATION

A power voltage of 5 V is applied to the A/C pressure sensor connector power terminal from the engine-ECU connector terminal ACP5&BVS5 and earthed to the engine-ECU connector terminal ACPE&BVSE from the A/C pressure sensor connector earth terminal.
The sensor signal is inputted to the engine-ECU connector terminal AC/P from the A/C pressure sensor connector output terminal.

FUNCTION

The A/C pressure sensor detects a change in A/C refrigerant pressure and inputs the signal to the engine-ECU.

TROUBLE JUDGEMENT

Check Conditions

After 2 seconds since the ignition switch is turned ON or since the completion of engine start.
Battery positive voltage is more than 10 V and is less than 16.5 V.

Judgement Criterion

Sensor output voltage is 0.2 V or less for 4 seconds.

FAIL-SAFE AND BACKUP FUNCTION

None

PROBABLE CAUSES

Failed A/C pressure sensor
Open/short circuit or harness damage in A/C pressure sensor circuit or loose connector contact
Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III data list

Refer to Data List Reference Table .

Item 172: A/C pressure sensor (voltage)
Item 175: A/C pressure sensor (pressure)

Q. Are the check results normal?

	Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).

	Go to Step 2.

STEP 2. Perform voltage measurement at A/C pressure sensor connector.

Disconnect connector, and measure at harness side.
Ignition switch: ON
Voltage between terminal ACP5&BVS5 line and earth.

OK: 4.9 - 5.1 V

Q. Is the check result normal?

	Go to Step 6.

	Go to Step 3.

STEP 3. Perform voltage measurement at engine-ECU connector

Measure engine-ECU terminal voltage.
Disconnect A/C pressure sensor connector.
Ignition switch: ON
Voltage between terminal ACP5&BVS5 and earth.

OK: 4.9 - 5.1 V

Q. Is the check result normal?

	Check of open circuit in ACP5&BVS5 line between A/C pressure sensor connector and engine-ECU connector.

	Go to Step 4.

STEP 4. Check of short to earth in ACP5&BVS5 line between A/C pressure sensor connector and engine-ECU connector.

Q. Are the check results normal?

	Go to Step 5.

	Repair the connector(s) or wiring harness.

STEP 5. M.U.T.-III data list

Refer to Data List Reference Table .

Item 172: A/C pressure sensor (voltage)
Item 175: A/C pressure sensor (pressure)

Q. Are the check results normal?

	Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).

	Replace the engine-ECU.

STEP 6. Perform voltage measurement at A/C pressure sensor connector.

Use special tool test harness (MB991348) to connect connector, and measure at pick-up harness.
Ignition switch: ON
Voltage between terminal ACP5&BVS5 line and earth.

OK: 4.9 - 5.1 V

Q. Is the check result normal?

	Go to Step 7.

	Repair or replace the connector(s), or check and repair the harness of damage in ACP5&BVS5 line between A/C pressure sensor connector and engine-ECU connector.

STEP 7. Perform voltage measurement at A/C pressure sensor connector.

Use special tool test harness (MB991348) to connect connector, and measure at pick-up harness.
Engine: Running at idle.
Perform the simple inspection for the A/C pressure sensor (Refer to GROUP 55A - On-vehicle Service - Simple Inspection of A/C Pressure Sensor ).
Voltage between terminal AC/P line and earth.

OK: Relationship between the manometer indication and the output voltage should comply with the graph.

Q. Is the check result normal?

	Go to Step 9.

	Go to Step 8.

STEP 8. Check of short to earth AC/P line between A/C pressure sensor connector and engine-ECU connector.

Q. Is the check result normal?

	Replace the A/C pressure sensor.

	Repair the connector(s) or wiring harness.

STEP 9. Perform voltage measurement at engine-ECU connector

Measure engine-ECU terminal voltage.
Engine: Running at idle.
Perform the simple inspection for the A/C pressure sensor (Refer to GROUP 55A - On-vehicle Service - Simple Inspection of A/C Pressure Sensor ).
Voltage between terminal code AC/P and earth.

OK: Relationship between the manometer indication and the output voltage should comply with the graph.

Q. Is the check result normal?

	Go to Step 5.

	Repair or replace the connector(s), or check and repair the harness of open circuit, and damage in AC/P line between A/C pressure sensor connector and engine-ECU connector.