Hydraulic Pump Relay Circuit Low
Diagnostic trouble code P0947 indicates that the transmission control module has detected a lower than expected voltage in the hydraulic pump relay control circuit. This typically means the circuit is shorted to ground or has high resistance, preventing the relay from properly activating the transmission hydraulic pump.
This code is considered high severity because a lack of hydraulic pressure can prevent the transmission from shifting gears, potentially leaving the vehicle stranded or causing internal transmission damage.
Common symptoms
- Illuminated Check Engine Light
- Transmission slipping or harsh shifting
- Vehicle stuck in a single gear (limp mode)
- Inability to engage drive or reverse
- Auto start/stop system disabled (if equipped)
Likely causes
- Faulty transmission hydraulic pump relay
- Blown fuse or fusible link in the pump circuit
- Damaged wiring or loose connections causing a short to ground
- Defective transmission hydraulic pump motor
- Faulty Transmission Control Module (TCM)
What to check before replacing parts
Check the transmission hydraulic pump fuse and relay.
Look for: A blown fuse or a relay that fails to click or lacks continuity when energized indicates a primary power delivery failure.
Inspect the wiring harness and connectors for the hydraulic pump relay circuit.
Look for: Look for chafed wires, corrosion, or melted connectors that could cause a short to ground or high resistance.
Test the hydraulic pump relay control circuit for voltage and ground.
Look for: Using a multimeter, verify that the TCM is sending the correct command voltage to the relay; a reading near zero when commanded on indicates a wiring or module issue.
Measure the resistance of the hydraulic pump motor.
Look for: An out-of-spec resistance reading or a direct short to ground in the pump motor indicates internal failure drawing excessive current.
Check the TCM output for the relay control circuit.
Look for: If wiring and the relay are good but the TCM fails to output the correct voltage to trigger the relay, the module itself may be faulty.
This page explains the generic P0947 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
Gear guide: Best OBD2 ScannersRead this code yourself next time — from $20 Bluetooth dongles to bidirectional scan tools.Rather have a pro handle it? Find a vetted local mechanic.