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DTC codes / P09xx · Transmission / P094B

P094BHydraulic Pump Stuck On

P094B indicates that the transmission control module (TCM) has commanded the electric hydraulic pump to turn off, but the pump continues to run or is detected as stuck in the on state. The computer monitors pump relay feedback or current draw and sets this code when the pump circuit remains active longer than expected, often due to a stuck relay or shorted control circuit.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaTransmission

Symptoms you may notice

  • Illumination of the check engine light or transmission warning light, often with no other symptoms
  • Transmission may enter limp mode with harsh or delayed shifting
  • Battery drain if the pump runs continuously after the vehicle is shut off
  • Overheating of the transmission fluid or pump motor due to continuous operation
  • Audible whirring or humming noise from the transmission area with the key on or engine off

Common causes, most likely first

  1. Stuck-closed hydraulic pump relay, keeping power applied to the pump
  2. Short to power in the control circuit between the TCM and the pump relay
  3. Faulty transmission control module (TCM) internal driver failure holding the pump on
  4. Failed hydraulic pump motor with internal short or seized bearing drawing current continuously
  5. Corroded or damaged wiring harness causing a short to voltage in the pump circuit
  6. Low transmission fluid level or restricted filter causing the pump to run excessively

How to diagnose and fix it

  1. Verify the code with a scan tool and check for any related transmission codes before clearing
  2. Inspect the hydraulic pump relay and swap it with an identical known-good relay to see if the code returns
  3. Measure voltage at the pump connector with the key off to confirm whether power is being applied when it should not be
  4. Check the control circuit between the TCM and relay for shorts to power using a wiring diagram and multimeter
  5. Test the pump motor for excessive current draw or internal short using a clamp-on ammeter
  6. If the relay and wiring are good, diagnose the TCM driver circuit or replace the TCM as needed
  7. Clear codes and perform a road test to confirm the pump shuts off correctly and the code does not reset

Before you replace the transmission pump

  • A stuck relay is the most common cause of this code, yet many technicians replace the pump or TCM first without testing the relay.
  • The code can set intermittently if the relay sticks only when hot, so a cold-engine test may not reveal the fault.
  • A shorted pump motor can mimic a stuck relay by drawing current continuously, so always test the motor circuit separately.
  • Some vehicles use a solid-state relay integrated into the TCM, making the TCM itself the likely culprit when no external relay is found.
  • A weak battery or low charging voltage can cause the TCM to misreport pump status, so check battery health before condemning modules.

Can I keep driving with P094B?

You can usually drive the vehicle short distances to a repair shop, but avoid long trips or leaving the vehicle parked with the key on, as the pump may run continuously and drain the battery or overheat the transmission fluid. If the transmission enters limp mode, limit driving to essential trips only.

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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