P0945
Hydraulic Pump Relay/Control Circuit/Open
Transmission controls
Generic OBD-II
High
What it means
P0945 means the control circuit for the transmission's hydraulic pump relay is open or malfunctioning. On transmissions that rely on an electric pump for line pressure, this can leave the gearbox without the pressure it needs to engage or shift. The engine still starts, but the transmission may not drive properly — treat it as a get-it-looked-at-now fault.
High
Can I keep driving? Limited — if the hydraulic pump can't run, the transmission may lose pressure and fail to engage or shift; avoid driving until it's diagnosed.
Common symptoms
What you'll notice
- Check-engine light on
- Non-operational hydraulic pump
- Loss of line pressure / failure to engage gears
- Harsh shifting or transmission won't shift
- Transmission may enter limp mode or not drive
Common causes
Most likely first
- Faulty hydraulic pump relayLikely
- Open or short in the relay control-circuit wiringCommon
- Loose or corroded connectors / damaged harnessCommon
- Faulty hydraulic pumpLess often
- Faulty transmission control module (TCM) — least likelyLess often
How to diagnose & fix
Work through it in order
- Confirm the code and locate the hydraulic pump relay.
- Inspect the relay, connectors, and control wiring for opens or corrosion.
- Test the relay and its control signal from the TCM.
- Verify the hydraulic pump runs and builds pressure.
- Repair wiring or replace the relay/pump as confirmed. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0945?+
Treat this as a stop-and-diagnose fault. Without the hydraulic pump the transmission can lose the pressure it needs to engage or shift, which risks leaving you stranded or damaging the gearbox.
Can I just clear P0945?+
It returns until the relay, its control wiring, or the pump is repaired.
Related codes
Often seen with P0945
Read & clear P0945 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX