OBD-II Generic Error Code P0945: How to Fix It

Q: Can I drive my car with a P0945 code?

It is not recommended to drive long distances or under heavy load with a P0945 code active. This fault indicates the hydraulic pump relay circuit is open, which can result in reduced or lost hydraulic pressure in the transmission. This may cause harsh shifting, slipping, or even transmission damage if ignored. Drive only short distances to get the vehicle to a repair location, and avoid towing or hauling.

Q: What causes the P0945 code to appear?

The most common causes of P0945 include a faulty or burned-out hydraulic pump relay, corrosion or damage in the relay socket terminals, an open or broken wire in the relay control circuit, a blown fuse in the transmission or hydraulic pump circuit, or in rare cases, a faulty transmission control module (TCM). Moisture intrusion into connectors is also a frequent culprit.

Q: How much does it cost to fix a P0945 code?

If the fix is simply replacing the hydraulic pump relay, costs are very low — typically $10 to $30 for the part alone. If wiring repairs are needed, labor costs can range from $75 to $150 per hour at a shop, and the total repair could run $150 to $400 depending on the extent of the damage. TCM replacement or reprogramming is the most expensive scenario, potentially costing $500 to $1,500 or more depending on the vehicle.

Q: Will replacing the relay always fix P0945?

Not always. While a failed relay is one of the most common causes, P0945 can also be triggered by wiring faults, connector corrosion, or a blown fuse. If replacing the relay does not clear the code, you need to continue diagnosing the circuit using a multimeter and wiring diagram to check for open circuits, broken wires, or grounding issues.

Q: Is P0945 the same as P0944?

They are closely related but not the same. P0944 refers to hydraulic pressure unit loss of pressure, while P0945 specifically identifies an open circuit condition in the hydraulic pump relay circuit. Both indicate hydraulic system problems, but P0945 points more directly to an electrical fault in the relay circuit rather than a pressure-related mechanical issue. It is common for both codes to appear together.

Abstract

The OBD-II error code P0945 indicates a problem with the hydraulic pump relay circuit, specifically an open circuit condition. This means the transmission control module (TCM) is detecting that the electrical circuit responsible for operating the hydraulic pump relay is broken or not functioning as expected. Left unaddressed, this fault can cause transmission performance issues, loss of hydraulic pressure, and potential damage to your transmission system.