Powertrain, generic · Transmission

P0945 Hydraulic Pump Relay/Control Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

The control module drives the motor of the hydraulic pump through a relay or a direct output. This code reports a general circuit fault or an open in that control path, so the pump cannot be switched reliably. No manufacturer documents this exact code publicly. The layout is shown by a ZF patent for an automated gearbox, in which a motor-driven pump draws oil from a reservoir and charges a pressure accumulator behind a one-way valve, with shut-off valves feeding the shift cylinders. CARB requires circuit checks on transmission outputs. P0946 is the plausibility fault, P0947 and P0948 low and high; P094E covers the pump supply instead of the control side. Without the pump the gearbox soon runs out of pressure.

Likely causes

Pump relay coil open or relay not seated
Open control wire or loose terminal between module and relay
Failed output stage in the control module

Symptoms

  • Warning light on
  • Pump does not run, pressure is not built
  • Gears cannot be changed or auto stop-start disabled

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–500
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

hydraulic pump relaywiring harnesstcm

Related codes

P0946P0947P0948P094EP0942

References: patents.google.com, law.cornell.edu.