P0945: Hydraulic Pump Relay/Control Circuit/Open

What it means

The hydraulic pump relay/control circuit reports a circuit/open condition. Pump cannot be commanded reliably.

At a glance

• Usually lights the check-engine light
• The engine or gearbox may go into limp mode

How it works

The hydraulic pump relay control circuit lets the TCM command the relay that powers the hydraulic pump. P0945 sets when the circuit is open, such as from a broken control wire, failed relay coil, or a terminal that has backed out, so the pump may not respond reliably.

Common causes

Most likely first.

1. Open in relay control wire
2. Open relay coil
3. Pin pushed back out of connector body

Symptoms

• Check engine or transmission warning light on
• Harsh, delayed, or missing shifts
• Possible limp mode (locked in one gear)
• Slipping or shuddering during gear changes

How to diagnose it

1. Record freeze-frame data and scan for related pump or relay codes to see whether the fault coincides with a pump command.
2. Inspect the relay and its connectors for a loose fit, a pushed-back terminal, corrosion, or heat damage.
3. Trace the relay control wire for breaks, chafing, or disconnected sections between the relay and the controlling module.
4. Check relay coil continuity and the control circuit for an open, following the manufacturer's wiring information and specification.
5. If the wiring and relay pass, verify that the module is commanding the circuit and inspect its connector before considering a module fault.

Common fixes

• Seat the relay and repair any pushed-back connector terminal.
• Repair an open or damaged relay control wire.
• Replace a relay with an open coil.
• Repair a faulty module connection or control output if circuit testing confirms the problem.

Can I keep driving?

Avoid driving if shifts are delayed, slipping, or the vehicle enters limp mode, since the pump may not be commanded when needed. If the transmission loses drive or shifts unpredictably, stop and arrange recovery.