Nissan Maxima Service and Repair Manual: P0840 transmission fluid pressure SEN/SW A

The secondary pressure sensor detects secondary pressure of CVT and sends a signal to the TCM.

DTC Logic

DTC DETECTION LOGIC

DTC CONFIRMATION PROCEDURE

NOTE: Immediately after performing any "DTC CONFIRMATION PROCEDURE", always turn ignition switch OFF.

Then wait at least 10 seconds before performing the next test.

1.CHECK DTC DETECTION

With CONSULT

1.  Turn ignition switch ON.
2.  Select "Data Monitor" in "TRANSMISSION".
3.  Check that output voltage of CVT fluid temperature sensor is within the range below.

ATF TEMP SEN : 1.0 - 2.0 V

If it is out of range, drive the vehicle to decrease the voltage (warm up the fluid) or stop engine to increase the voltage (cool down the fluid)

4. Start engine and wait for at least 5 consecutive seconds.

With GST

Follow the procedure "With CONSULT".

Diagnosis Procedure

Regarding Wiring Diagram information, refer to TM-126, "Wiring Diagram".

1.CHECK INPUT SIGNAL

1.  Start engine.
2.  Check voltage between TCM connector terminal and ground.

2.CHECK POWER AND SENSOR GROUND

Check voltage between TCM terminals.

3.CHECK HARNESS BETWEEN TCM AND CVT UNIT (SECONDARY PRESSURE SENSOR) (PART 1)

1.  Turn ignition switch OFF.
2.  Disconnect TCM connector and CVT unit connector.
3.  Check continuity between TCM vehicle side harness connector terminal and CVT unit vehicle side harness connector terminal.

4.CHECK HARNESS BETWEEN TCM AND CVT UNIT (SECONDARY PRESSURE SENSOR) (PART 2)

Check continuity between TCM vehicle side harness connector terminal and ground.

5.CHECK HARNESS BETWEEN TCM AND CVT UNIT (SENSOR POWER AND SENSOR GROUND) (PART 1)

1.  Turn ignition switch OFF.
2.  Disconnect TCM connector and CVT unit connector.
3.  Check continuity between TCM vehicle side harness connector terminals and CVT unit vehicle side harness connector terminals.

6.CHECK HARNESS BETWEEN TCM AND CVT UNIT (SENSOR POWER AND SENSOR GROUND) (PART 2)

Check continuity between TCM vehicle side harness connector terminals and ground.

7.CHECK TCM

1.  Replace with the same type of TCM. Refer to TM-168, "Exploded View".
2.  Connect each connector.
3.  Perform "DTC CONFIRMATION PROCEDURE". Refer to TM-85, "DTC Logic".

8.DETECT MALFUNCTIONING ITEMS

Check TCM connector pin terminals for damage or loose connection with harness connector.