Subaru Crosstrek Service Manual: Dtc p0843 transmission fluid pressure sensor/switch "a" circuit high

DTC detecting condition:

Immediately at fault recognition

Trouble symptom:

Shift characteristics malfunction

CAUTION:

Use the check board when measuring the TCM terminal voltage and resistance.

1.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) Depress the brake pedal, and shift the select lever to “D” range.

4) Shift the select lever to “P” range.

5) Stabilize the engine speed at idle.

6) Read the data of «Actual Secondary Pressure» using Subaru Select Monitor.

Is the «Actual Secondary Pressure» 0.5 — 1.5 MPa?

Check for poor contact of connector.

Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0843 TRANSMISSION FLUID PRESSURE SENSOR/SWITCH "A" CIRCUIT HIGH">Go to Step 2.

2.CHECK HARNESS.

1) Turn the ignition switch to OFF.

2) Disconnect the TCM connector.

3) Disconnect the transmission connector.

4) Turn the ignition switch to ON.

5) Measure the voltage between TCM connector and chassis ground.

Connector & terminal

(B54) No. 5 (+) — Chassis ground (−):

(B54) No. 33 (+) — Chassis ground (−):

Is the voltage approx. 0 V?

Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0843 TRANSMISSION FLUID PRESSURE SENSOR/SWITCH "A" CIRCUIT HIGH">Go to Step 3.

Repair the short circuit of harness.

3.CHECK HARNESS.

1) Turn the ignition switch to OFF.

2) Measure the resistance between TCM connector terminals.

Connector & terminal

(B54) No. 5 — (B54) No. 33:

Is the resistance less than 1 ??

Repair the short circuit of harness.

Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0843 TRANSMISSION FLUID PRESSURE SENSOR/SWITCH "A" CIRCUIT HIGH">Go to Step 4.

4.CHECK TRANSMISSION HARNESS.

1) Disconnect the secondary pressure sensor connector.

2) Turn the ignition switch to ON.

3) Measure the voltage between transmission connector and chassis ground.

Connector & terminal

(T3) No. 11 (+) — Chassis ground (−):

(T3) No. 12 (+) — Chassis ground (−):

Is the voltage approx. 0 V?

Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0843 TRANSMISSION FLUID PRESSURE SENSOR/SWITCH "A" CIRCUIT HIGH">Go to Step 5.

Repair the short circuit of harness.

5.CHECK TRANSMISSION HARNESS.

1) Turn the ignition switch to OFF.

2) Measure the resistance between transmission connector terminals.

Connector & terminal

(T3) No. 11 — (T3) No. 12:

Is the resistance less than 1 ??

Repair the short circuit of harness.

Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0843 TRANSMISSION FLUID PRESSURE SENSOR/SWITCH "A" CIRCUIT HIGH">Go to Step 6.

6.CHECK POWER SUPPLY FOR SECONDARY PRESSURE SENSOR.

1) Connect the TCM connector.

2) Connect the transmission connector.

3) Turn the ignition switch to ON.

4) Measure the voltage between secondary pressure sensor connector terminals.

Connector & terminal

(AT6) No. 1 (+) — (AT6) No. 3 (−):

Is the voltage 4.5 V or more?

Replace the secondary pressure sensor. Secondary Pressure Sensor"> If the replacement of the sensor do not eliminate the malfunction, replace the TCM. Transmission Control Module (TCM)">

Check for poor contact of connector, and if no fault is found, replace the TCM. Transmission Control Module (TCM)">

• Detect short circuit to power supply or open circuit of the transmission line pressure sensor 5 V system.

• Judge as NG if the voltage detected by the transmission line pressure sensor is higher than the predetermined value.

Dtc p0842 transmission fluid pressure sensor/switch "a" circuit low

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