Powertrain, generic · Transmission

P0947 Hydraulic Pump Relay/Control Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

The voltage on the control line of the hydraulic pump relay or driver is lower than the module expects for the commanded state. Usually the line is shorted to ground or the relay coil is shorted, so the output may be overloaded and the pump runs when it should not, or the driver shuts down. No manufacturer documents this exact code publicly. The hydraulic unit it belongs to, a motor-driven pump that charges an accumulator for the shift and clutch cylinders of an automated gearbox, is described in a ZF patent. CARB requires circuit checks on transmission outputs. P0948 is the high counterpart, P0945 the open fault, P0946 plausibility. Pressure supply for shifting may fail.

Likely causes

Relay control wire chafed and shorted to ground
Shorted relay coil
Damaged output stage in the control module

Symptoms

  • Warning light on
  • Pump runs continuously or not at all
  • Gearbox in limp mode or 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

P0945P0946P0948P094E

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