Powertrain, generic · Transmission

P0946 Hydraulic Pump Relay/Control Circuit Range/Performance

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

The pump control circuit is electrically intact, but its behaviour does not match the command, for example a pump that keeps running after being switched off, or one that switches but is not followed by the expected feedback. No manufacturer documents this exact code publicly. In the hydraulic unit of an automated gearbox, as shown in a ZF patent, the pump only has to run until the accumulator is charged; a relay that sticks or switches late upsets that cycle. CARB requires functional checks on transmission outputs. P0945 is the general circuit or open fault, P0947 and P0948 the low and high faults, P094B a pump stuck on regardless of the relay. A pump that never stops drains the battery and wears quickly.

Likely causes

Relay contacts welded or sticking
Pump supply or control wire shorted to battery voltage
Faulty pump state feedback or control module

Symptoms

  • Pump keeps running after switch-off
  • Warning light on
  • Auto stop-start not available
  • Battery discharged after parking

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

P0945P0947P0948P094B

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