DTC P0843: Transmission Fluid Pressure Sensor/Switch "A" Circuit High: Notes

WARNING: This page is about a different variant/trim than selected.

1. -

DTC detecting condition:

Immediately at fault recognition

Trouble symptom:

Shift characteristics malfunction

Wiring diagram:

CVT control system Ref. to WIRING SYSTEM (CROSSTREK MODEL (EXCEPT FOR HEV))>CVT CONTROL SYSTEM .

Courtesy of SUBARU OF AMERICA, INC.

CAUTION:

Use CHECK BOARD when measuring the TCM terminal voltage and resistance.
After servicing or replacing faulty parts, perform the last step of the basic diagnostic procedure. Ref. to TRANSMISSION (DIAGNOSTICS) (CROSSTREK MODEL)>BASIC DIAGNOSTIC PROCEDURE .

Courtesy of SUBARU OF AMERICA, INC.

CHECK INPUT SIGNAL FOR TCM .
1. Start the engine.
2. Warm up until the ATF temperature reaches to 40 - 70°C (104 - 158°F).
3. Set the select lever to "D" range.
4. Drive at 2 km/h or more.
5. Shift the select lever to "P" range.
6. Stabilize the engine speed at idle.
7. Using the Subaru Select Monitor, read data of [Actual line press.] in the [Data Monitor] of [Transmission]. Ref. to TRANSMISSION (DIAGNOSTICS) (CROSSTREK MODEL)>DATA MONITOR .
Is [Actual line press.] 0.5 - 1.5 [MPa]?

Yes : Check for poor contact of connector.

No : Go to 2.
CHECK HARNESS .
1. Turn the ignition switch to OFF.
2. Disconnect the TCM connector.
3. Disconnect the line pressure sensor connector.
4. Turn the ignition switch to ON.
5. Measure the voltage between TCM connector and chassis ground.
  Connector & terminal
  
  (T10) No. 4 (+) - Chassis ground (-):
  
  (T10) No. 17 (+) - Chassis ground (-):
Is the voltage approx. 0 V?

Yes : Go to 3.

No : Repair the short circuit of harness.
CHECK HARNESS .
1. Turn the ignition switch to OFF.
2. Measure the resistance between TCM connector terminals.
  Connector & terminal
  
  (T10) No. 4 - (T10) No. 17:
Is the resistance less than 1 Ω?

Yes : Repair the short circuit of harness.

No : Go to 4.
CHECK LINE PRESSURE SENSOR POWER SUPPLY .
1. Connect the TCM connector.
2. Turn the ignition switch to ON.
3. Measure the voltage between line pressure sensor connector terminals.
  Connector & terminal
  
  (AT2) No. 1 (+) - (AT2) No. 3 (-):
Is the voltage 4.5 V or more?

Yes : Replace the line pressure sensor. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR580 CROSSTREK)>LINE PRESSURE SENSOR .

No : Check for poor contact of connector, and if no fault is found, replace the TCM. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR580 CROSSTREK)>TRANSMISSION CONTROL MODULE (TCM) .