P0934 Code: Hydraulic Pressure Sensor Circuit Low

What the P0934 code means

Automated manual transmissions (Opel Easytronic, Fiat Dualogic, Toyota MMT, BMW SMG, Ford Durashift, Volkswagen ASG) and many dual clutch transmissions use electric or hydraulic actuators to disengage the clutch, to choose the gear plane (select) and to engage the gear (shift). The transmission computer watches every actuator with position sensors. On hydraulic systems, a sensor measures accumulator pressure so the computer can control the pump.

The sensor gets a 5 volt reference and a ground from the computer and sends back a signal between about 0.5 and 4.5 volts. A low signal, which is what the P0934 code reports, usually comes from a signal wire shorted to ground or from a missing reference voltage.

If the signal fails, the pump can run with no control or fail to switch on, and the transmission loses the pressure it needs to shift. After any repair of these components you must run the transmission relearn procedures with a scan tool (clutch touch point, select and shift positions). Without them the transmission will not work properly.

To confirm the fault, unplug the component with the key on and watch the reading or the code. If the value jumps to the opposite extreme, the wiring is good and the component is the one pulling the signal to ground. If nothing changes, look for the short in the wire, starting where the harness rubs against the engine, the chassis or the exhaust.

P0934 code symptoms

• Check engine light on.
• Pressure loss, or a pump running with no control.
• The pump runs constantly or cannot be heard at all.
• The transmission does not shift.

Likely causes of the P0934 code

1. Signal wire shorted to ground because the harness rubs against the engine, the chassis or a bracket.
2. Shorted reference supply. If several sensors fail at once, suspect the shared reference.
3. Damaged sensor with an internal short.
4. Connector with water or corrosion, which creates a path to ground.

How to diagnose the P0934 code step by step

1. Read the sensor value on the scan tool and compare it with what you expect.
2. Inspect the connector for corrosion, water or loose pins.
3. Check supply and ground with the key on: the reference should be correct and the ground voltage drop under 0.1 volts.
4. Measure the signal with the connector attached and see whether it changes with the condition.
5. Do a wiring wiggle test with the scan tool in graphing mode.
6. Check the continuity of each wire to the computer (under 1 ohm).
7. Check the hydraulic fluid level.

How to fix the P0934 code

• Repair the connector or the wiring.
• Replace the sensor if the tests confirm it is bad.
• Correct the real condition if one exists.
• Clear the codes and verify with a road test.

Technical reference data

• 5 volt reference, ground and a signal proportional to pressure.
• Approximate values only: check the manufacturer data for your vehicle.

Brand-specific notes

This code is very common on automated manual transmissions. On many hydraulic systems the actuator fluid is a specific type and the reservoir should be checked regularly.

P0934 on Opel

Very common on the Opel Easytronic.

P0934 on Fiat

Very common on the Fiat Dualogic.

P0934 on Toyota

Very common on the Toyota MMT.

P0934 on Smart

Seen on Smart vehicles with an automated manual transmission.

P0934 on BMW

Very common on the BMW SMG.

Frequently asked questions about P0934