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P0637 – Power Steering Control Circuit High (OBD2)

P0637 means "Power Steering Control Circuit High". The voltage in the power steering pressure sensor / control circuit is above the permitted maximum. For most sensors this points to an open signal or ground wire – the signal "floats" up to the reference voltage – or to a short to voltage.

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P0637 quick summary

Fault codeP0637
MeaningPower Steering Control Circuit High
SystemPowertrain (Engine & Transmission)
VehiclesGeneric OBD2
SeverityLow
Can I drive?Yes. Be careful when manoeuvring at low speed, as the engine may stall.
Repair cost€20 – €300

How power steering signals are used by the engine

The engine control unit monitors power steering pressure or controls power steering assistance, so it can raise the idle when steering at standstill; these codes cover the sensor and control circuits.

On cars with hydraulic power steering, a pressure sensor or switch tells the engine control unit when the pump is working hard (for example when turning the wheel at standstill), so it can raise the idle to prevent stalling. Some systems also have an electrically controlled steering assistance valve.

Codes P0550–P0554 report faults in the power steering pressure sensor circuit; P0635–P0637 in the power steering control circuit.

A faulty signal may cause the engine to stall or the idle to dip when manoeuvring. Steering assistance itself usually still works on hydraulic systems.

On VAG vehicles (VW, Audi, Škoda, Seat, Cupra), VCDS and older VAG testers can show this code as the five-digit VAG code 17021 (P0637). Both numbers mean the same fault.

Symptoms of P0637

  • Engine stalls or idle dips when turning the wheel at standstill
  • Check Engine light on
  • Steering feels heavier (control circuit faults)
  • Power steering fluid leak near the sensor
  • Often no other symptoms

Most common causes of P0637 (most likely first)

Mechanic's Pro Tip

Power steering pressure switches often leak fluid into their own connector – clean the connector when replacing the sensor.

  1. 1.Open circuit in the signal or ground wire

    Most likely

    A loose ground connection is a very common cause.

  2. 2.Signal wire shorted to the 5 V reference or battery voltage

  3. 3.Faulty power steering pressure sensor / control

  4. 4.Fluid leak at the sensor

  5. 5.Wiring or connector fault

  6. 6.Low power steering fluid

  7. 7.Control valve or module fault

Step-by-step diagnostic guide

  1. 1

    Read codes and check fluid

    Read all codes and check the power steering fluid level.

  2. 2

    Check signal and ground

    With the ignition on and the power steering pressure sensor / control plugged in, back-probe the signal and ground wires. A signal stuck at reference or battery voltage points to an open ground/signal wire or a short to voltage.

    Multimeter: Ground wire to battery negative: below about 0.1 V. Signal stuck at about 5 V (or 12 V) = open or short to voltage.

  3. 3

    Watch the sensor signal

    Watch the sensor value in live data while turning the wheel at standstill – it must change.

  4. 4

    Check the sensor wiring

    Check the connector and wiring for damage and fluid contamination.

  5. 5

    Measure the sensor

    Check the supply and signal according to the specification.

  6. 6

    Replace and verify

    Replace the sensor, top up fluid and check that the idle stays stable when steering.

Frequently asked questions

Can I keep driving with P0637?

Yes. Be careful when manoeuvring at low speed, as the engine may stall.

How much does it cost to fix P0637?

Typical repair costs are 20 € – 300 €, depending on the cause and the vehicle. The most common fixes are: open circuit in the signal or ground wire; signal wire shorted to the 5 V reference or battery voltage; faulty power steering pressure sensor / control. Always confirm the cause with the tests above before buying parts.

Does the code affect the steering?

On hydraulic systems usually not; it mainly affects idle control. Control circuit faults can reduce assistance.

Why does the engine stall when I turn the wheel?

The pump loads the engine. If the control unit does not know, it does not raise the idle in time.

What is the difference between P0637 and similar codes?

P0637 belongs to a group of codes for the same component that differ in the type or location of the fault: P0551 – Power Steering Pressure Sensor Circuit Range/Performance; P0552 – Power Steering Pressure Sensor Circuit Low Input; P0553 – Power Steering Pressure Sensor Circuit High Input; P0554 – Power Steering Pressure sensor Circuit Intermittent; P0635 – Power Steering Control Circuit; P0636 – Power Steering Control Circuit Low. The tests on this page apply to the whole group; the type of fault tells you where to start.

Related fault codes

This guide is for information only. Working on vehicles can be dangerous — if you are unsure, have the car checked by a qualified mechanic. Values can differ between model years; always check the manufacturer's repair information.