P0948Generic code

P0948 Code: Hydraulic Pump Relay Circuit High

The P0948 code means the hydraulic pump relay control circuit shows high voltage, which points to an open circuit or a short to voltage. It can lead to a loss of hydraulic pressure. Start with the connector, because a loose or broken one is the usual cause.

Severity
High
Can I keep driving?
Yes, but with caution
Estimated cost
$100 to $1,200
Difficulty
Medium
System
Transmission
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0948 code means

Automated manual transmissions (Opel Easytronic, Fiat Dualogic, Toyota MMT, BMW SMG, Ford Durashift, Volkswagen ASG) and many dual-clutch gearboxes use electric or hydraulic actuators to release the clutch, pick the gear plane (selection) and engage the gear (engagement). The transmission computer watches every actuator through position sensors. In hydraulic systems, an electric pump keeps up the accumulator pressure that operates the clutch and the shifts, and the computer turns it on through a relay.

The computer monitors the control circuit from its own driver transistor. The P0948 code means the voltage in the control circuit is high, which is either an open circuit or a short to voltage. Before you change the component, check the fuse, the relay, the connector and the wiring, because those are the usual culprits.

If the pump does not run, the system loses pressure and the gearbox stops shifting. If the relay sticks closed, the pump runs nonstop and overheats. After any repair on these parts, the gearbox learning procedures (clutch touch point, selection positions and engagement positions) have to be run with a scan tool. Without them the transmission will not work properly.

To confirm it, measure the continuity of each wire between the component connector and the computer connector with the key off. It should be under 1 ohm. An infinite reading means the wire is open. If the wiring is good, measure the component itself: infinite resistance confirms it is open inside.

P0948 code symptoms

  • Check engine light or another warning light on.
  • Loss of hydraulic pressure.
  • The gearbox will not engage gears or stays in neutral.
  • Transmission or engine light on.
  • Beep or warning message on the dash.

Likely causes of the P0948 code

  1. Loose or broken connector. The most common cause, especially after another repair.
  2. Open coil or motor. Infinite resistance.
  3. Control wire cut between the component and the computer.
  4. Short to 12 volts. The control wire touches another wire that carries voltage.

How to diagnose the P0948 code step by step

  1. Command the component with the scan tool and see whether it responds.
  2. Check the fuse and the relay. Measure voltage on both sides of the fuse and swap the relay with an identical one.
  3. Measure the supply at the connector. You should see battery voltage with the key on, or when the component is commanded.
  4. Measure the component resistance and compare it with the manual, then check the insulation to ground.
  5. Check the control wire for continuity to the computer and for shorts to voltage.
  6. Command the actuator with the scan tool and see whether it moves.
  7. Run the gearbox learning procedures after any repair.
  8. Check the hydraulic fluid level and look for leaks.

How to fix the P0948 code

  • Repair the connector, the wiring or the supply.
  • Replace the hydraulic pump relay if it does not respond when it has the right supply and command.
  • Clear the P0948 code and verify the repair.

Technical reference data

  • Electric actuator (DC motor) or hydraulic solenoid valve controlled by PWM.
  • Reference values only: check the manufacturer data for your vehicle.

Brand-specific notes

These are the makes where this family of codes turns up most. In many hydraulic systems the actuator fluid is a specific one, and the reservoir should be checked regularly.

P0948 on Opel

Very common on the Opel Easytronic.

P0948 on Fiat

Very common on the Fiat Dualogic.

P0948 on Toyota

Very common on the Toyota MMT.

P0948 on Smart

Very common on Smart cars with this style of transmission.

P0948 on BMW

Very common on the BMW SMG.

Frequently asked questions about P0948

Can I drive with a P0948 code?
With caution, and only as far as a shop. The gearbox can lose its gears at any moment.
What does the hydraulic pump relay do?
Automated manual transmissions (Opel Easytronic, Fiat Dualogic, Toyota MMT, BMW SMG, Ford Durashift, Volkswagen ASG) and many dual-clutch gearboxes use electric or hydraulic actuators to release the clutch, pick the gear plane (selection) and engage the gear (engagement). The transmission computer watches each actuator with position sensors. In hydraulic systems, an electric pump keeps up the accumulator pressure that operates the clutch and the shifts, and the computer switches it on through a relay.
Does the part always have to be replaced?
No. Check the fuses, relays, connectors and wiring first, since they cause most of these faults.
How much does it cost to fix P0948?
As a rough guide, between $100 and $1,200. A reseated connector or a repaired wire is cheap, and a new component costs more.
What does the P0948 code mean?
It means the voltage on the pump relay control circuit is too high. That points to an open circuit or a short to voltage.
Will a P0948 code clear itself?
Not if the connector is loose or a wire is cut, because the fault is still there. A one-time glitch may clear after several drive cycles.

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