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DTC codes / P09xx · Transmission / P094E

P094EHydraulic Pump Supply Voltage Circuit/Open

P094E indicates that the transmission control module (TCM) has detected an open circuit or supply voltage fault in the hydraulic pump circuit, which is responsible for providing pressurized fluid to the transmission's hydraulic system. The computer monitors the voltage on the supply circuit and sets this code when the voltage falls outside the expected range, typically indicating a break in the wiring or a failed pump motor.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaTransmission

Symptoms you may notice

  • Illumination of the check engine light or transmission warning light
  • Often no symptoms besides the warning light, especially if the pump is only intermittently used
  • Harsh or delayed transmission shifts due to insufficient hydraulic pressure
  • Transmission may enter limp mode or fail to engage gears
  • Whining or unusual noises from the transmission area if the pump is struggling

Common causes, most likely first

  1. Open or damaged wire in the hydraulic pump supply circuit (e.g., broken wire, corroded connector)
  2. Blown fuse or faulty relay supplying power to the hydraulic pump
  3. Failed hydraulic pump motor or internal pump assembly
  4. Poor ground connection for the pump circuit
  5. Faulty transmission control module (TCM) or power control module (PCM) not supplying voltage
  6. Corrosion or water intrusion in the connector at the pump

How to diagnose and fix it

  1. Check the fuse and relay for the hydraulic pump circuit and replace if blown or faulty
  2. Inspect the wiring harness and connectors at the pump and TCM for damage, corrosion, or loose pins
  3. Measure voltage at the pump connector with the key on and pump commanded on; compare to battery voltage
  4. Perform a voltage drop test on the supply and ground circuits to identify excessive resistance
  5. If voltage is present at the pump but it does not operate, test the pump motor directly with a known good power source
  6. Replace the hydraulic pump motor or assembly if it fails direct testing
  7. Clear the code and verify repair by test-driving and monitoring live data for the pump circuit

Don't overlook the pump ground circuit

  • A common oversight is focusing on the positive supply wire while ignoring the ground circuit; a bad ground can cause the same open-circuit code and mimic a failed pump.
  • The hydraulic pump may only run under specific conditions (e.g., during shifts or at certain temperatures), so an intermittent open circuit might not show up during a simple key-on test.
  • Corroded connectors at the transmission are frequent culprits, especially in areas with road salt or high humidity, and can cause voltage drops that set this code without a complete open.
  • A failed TCM driver can set this code even when all wiring and the pump are good, so don't replace the pump without verifying the TCM is actually commanding the pump on.
  • This code can be set by a low battery or charging system issue that causes supply voltage to drop below the threshold during pump operation, so always check battery health first.

Can I keep driving with P094E?

If the vehicle drives normally with only the warning light on, you can drive cautiously to a repair shop, but avoid heavy loads or aggressive driving. If the transmission is shifting harshly or has entered limp mode, stop driving and seek professional diagnosis to prevent further damage.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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