P0938 Hydraulic Oil Temperature Sensor Range/Performance

P0938 indicates hydraulic oil temperature sensor range/performance. The temperature signal exists but is implausible for operating conditions.

Code details

Generic OBD-II · P0

System: Transmission
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not replace hydraulic control parts until the temperature sensor response is checked over a real warm-up cycle.

Symptoms of P0938

Harsh, delayed, or slipping shifts, or being stuck in one gear.
Check-engine light, sometimes with limp-home mode.
Flaring RPM or a shudder under load.

Common causes of P0938

Low or degraded transmission fluid.
A failing speed sensor, shift solenoid, or pressure-control circuit.
Wiring, connector, or internal hydraulic/mechanical faults.

Useful checks before replacing parts

Compare hydraulic oil temperature rise with ambient, engine, transmission fluid, pump operation, and drive-cycle duration.
Inspect sensor mounting, connector condition, reference and ground stability, harness routing, and fluid condition affecting heat transfer.
Check whether the fault appears after cold soak, heat soak, long traffic operation, or rapid hydraulic pump cycling.

Related OBD-II codes

These nearby transmission entries can help compare wording and pin down the fault area.