Inspection Procedure 34
A/C Pressure Sensor SystemA/C Pressure Sensor Circuit Part 1:
A/C Pressure Sensor Circuit Part 2:
CIRCUIT OPERATION
- A 5-volt voltage is supplied to the A/C pressure sensor power terminal (terminal No. 3) from the PCM (terminal No. 46). The ground terminal (terminal No. 1) is grounded with the PCM (terminal No. 57).
- A voltage that is proportional to the A/C refrigerant pressure is sent from the A/C pressure sensor output terminal (terminal No. 2) to the PCM (terminal No. 62).
TECHNICAL DESCRIPTION
- The A/C pressure sensor detects the A/C refrigerant pressure and inputs it into the PCM.
- The PCM uses this signal for fuel injection mode control.
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- A/C pressure sensor failed.
- Open or shorted A/C pressure sensor circuit, or loose connector.
- PCM failed.
DIAGNOSIS
Required Special Tool:
- MB991502: Scan Tool (MUT-II)
STEP 1. Using scan tool MB991502, check data list item 3A: A/C Pressure Sensor.
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
1. Connect scan tool MB991502 to the data link connector.
2. Start the engine and run at idle.
3. Turn the A/C switch to the "ON" position.
4. Check the following items in the data list. Refer to, Data List Reference Table.
a. Item 3A: A/C Pressure Sensor.
5. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points.
NO: Go to Step 2.
STEP 2. Measure the sensor output voltage at A/C pressure sensor connector A-02 by backprobing.
1. Do not disconnect the connector A-02.
2. Start the engine and run at idle.
3. Turn the A/C switch to the "ON" position.
4. Measure the voltage between terminal No. 2 and ground by backprobing.
- When A/C refrigerant pressure is 1 kPa, voltage should measure between 1.8 and 2.0 volts.
- When A/C refrigerant pressure is 2 kPa, voltage should measure between 3.23 and 3.57 volts.
5. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage within the specified range?
YES: Go to Step 13.
NO: Go to Step 3.
STEP 3. Measure the sensor supply voltage at A/C pressure sensor connector A-02 by backprobing.
1. Do not disconnect the connector A-02.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No. 3 and ground by backprobing.
- Voltage should measure between 4.9 and 5.1 volts.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage between 4.9 and 5.1 volts?
YES: Go to Step 8.
NO: Go to Step 4.
STEP 4. Measure the sensor supply voltage at PCM connector C-111 by backprobing.
1. Do not disconnect the connector C-111.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No. 46 and ground by backprobing.
- Voltage should measure between 4.9 and 5.1 volts.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage between 4.9 and 5.1 volts?
YES: Go to Step 7.
NO: Go to Step 5.
STEP 5. Check connector C-111 at PCM and connector A-02 at A/C pressure sensor for damage.
Q: Is the connector in good condition?
YES: Go to Step 6.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.
STEP 6. Check for short circuit to ground between A/C pressure sensor connector A-02 (terminal No. 3) and PCM connector C-111 (terminal No. 46).
NOTE: Check harness after checking intermediate connector A-14. If intermediate connectors are damaged, repair or replace them. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.
Q: Is the harness wire in good condition?
YES: Replace the PCM. Then confirm that the malfunction symptom is eliminated.
NO: Repair it. Then confirm that the malfunction symptom is eliminated.
STEP 7. Check connector C-111 at PCM and connector A-02 at A/C pressure sensor for damage.
Q: Is the connector in good condition?
YES: Check the connector A-14 at intermediate connector for damage, and repair or replace as required. Refer to Harness Connector Inspection. If intermediate connector is in good condition, repair harness wire between A/C pressure sensor connector A-02 (terminal No. 3) and PCM connector C-111 (terminal No. 46) because of open circuit and harness damage. Then confirm that the malfunction symptom is eliminated.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.
STEP 8. Measure the ground voltage at A/C pressure sensor connector A-02 by backprobing.
1. Do not disconnect the connector A-02.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No. 1 and ground by backprobing.
- Voltage should measure 0.5 volt or less.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage 0.5 volt or less?
YES: Go to Step 11.
NO: Go to Step 9.
STEP 9. Check connector C-111 at PCM and connector A-02 at A/C pressure sensor for damage.
Q: Is the connector in good condition?
YES: Go to Step 10.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.
STEP 10. Check for open circuit and harness damage between A/C pressure sensor connector A-02 (terminal No. 1) and PCM connector C-111 (terminal No. 57).
NOTE: Check harness after checking intermediate connectors C-105 and C-116. If intermediate connectors are damaged, repair or replace them. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.
Q: Is the harness wire in good condition?
YES: Replace the PCM. Then confirm that the malfunction symptom is eliminated.
NO: Repair it. Then confirm that the malfunction symptom is eliminated.
STEP 11. Check connector C-111 at PCM and connector A-02 at A/C pressure sensor for damage.
Q: Is the connector in good condition?
YES: Go to Step 12.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.
STEP 12. Check for short circuit to ground and harness damage between A/C pressure sensor connector A-02 (terminal No. 2) and PCM connector C-111 (terminal No. 62).
NOTE: Check harness after checking intermediate connectors C-104 and C-116. If intermediate connectors are damaged, repair or replace them. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.
Q: Is the harness wire in good condition?
YES: Replace the A/C pressure sensor. Then confirm that the malfunction symptom is eliminated.
NO: Repair it. Then confirm that the malfunction symptom is eliminated.
STEP 13. Measure the sensor output voltage at PCM connector C-111 by backprobing.
1. Do not disconnect the connector C-111.
2. Start the engine and run at idle.
3. Turn the A/C switch to the "ON" position.
4. Measure the voltage between terminal No. 62 and ground by backprobing.
- When A/C refrigerant pressure is 1 kPa, voltage should measure between 1.8 and 2.0 volts.
- When A/C refrigerant pressure is 2 kPa, voltage should measure between 3.23 and 3.57 volts.
5. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage within the specified range?
YES: Go to Step 15.
NO: Go to Step 14.
STEP 14. Check connector C-111 at PCM and connector A-02 at A/C pressure sensor for damage.
Q: Is the connector in good condition?
YES: Check the connectors C-104 and C-116 at intermediate connectors for damage, and repair or replace as required. Refer to Harness Connector Inspection. If intermediate connectors are in good condition, repair harness wire between A/C pressure sensor connector A-02 (terminal No. 2) and PCM connector C-111 (terminal No. 62) because of open circuit and harness damage. Then confirm that the malfunction symptom is eliminated.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.
STEP 15. Check connector C-111 at PCM and connector A-02 at A/C pressure sensor for damage.
Q: Is the connector in good condition?
YES: Go to Step 16.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.
STEP 16. Using scan tool MB991502, check data list item 3A: A/C Pressure Sensor.
1. Connect scan tool MB991502 to the data link connector
2. Start the engine and run at idle.
3. Turn the A/C switch to the "ON" position.
4. Check the following items in the data list. Refer to, Data List Reference Table.
a. Item 3A: A/C Pressure Sensor.
5. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points.
NO: Replace the PCM. Then confirm that the malfunction symptom is eliminated.