P0945 Hydraulic Pump Relay Circuit/Open

P0945 points to a hydraulic pump relay circuit or open-circuit fault. The controller cannot complete the relay path used to power the hydraulic pump.

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 the pump before proving the relay control circuit and power supply are intact.

Symptoms of P0945

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 P0945

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

Check hydraulic pump relay feed, control, ground, output voltage, fuse supply, connector fit, and relay coil resistance.
Inspect pump wiring, relay socket terminals, module driver output, water intrusion, harness rub points, and voltage drop under load.
Compare pump command with relay output, pump current, pressure build, and pressure sensor response.

Related OBD-II codes

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