Powertrain, generic · Computer and auxiliary outputs

P0636 Power Steering Control Circuit Low

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

P0635–P0637 concern the control or signal circuit between engine module and power steering – depending on the maker the drive of an electro-hydraulic pump or the steering load signal the engine module uses to raise idle. CARB requires power steering components to be monitored only if another diagnostic uses them, so these codes are rare and maker-specific. Mercedes-Benz stores P0635 in the electric steering module itself (no assist after start, software update); no engine module table available to us uses P0635–P0637. P0636 means the voltage in this circuit is too low – the wire is shorted to ground, supply voltage is low, or the driver sees a low state although it commanded 'on'. No manufacturer threshold is published.

Likely causes

Signal or control wire shorted to ground (chafing)
Undervoltage from battery, alternator or ground
Steering module or pump module faulty internally
Engine module driver faulty

Symptoms

  • Power steering warning, heavy steering
  • Check engine light (depending on the maker)
  • Idle drops when steering

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–1,500
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

power steering control circuitpower steering moduleengine control module

Related codes

P0635P0637P0550P0552P0562

References: law.cornell.edu, en.wikipedia.org, static.nhtsa.gov.