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HO2S Heater Current Monitor Control Circuit Sensors 1

Jump to the fix

Severity

Medium

Can I keep driving?

Usually drivable, but get it diagnosed without delay.

First step

Read the freeze frame first and note whether the fault appeared cold, hot or during vibration

  • PPowertrain
  • 1Manufacturer-specific
  • 0Powertrain (Other)
  • 31Sequence number

What does it mean?

P1031 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Cylinder 1 Oil Supply Solenoid Valve Driver Voltage Implausible .

Symptoms

  • Check engine light on, frequently together with codes for the neighbouring cylinder solenoids
  • Rough or uneven idle because cylinder 1 does not switch its oil supply as commanded
  • Flat spot and a clear loss of pulling power when engine load changes
  • Ticking or louder valve-train noise from the cylinder head area
  • Engine may fall back into limp mode with a reduced rev limit
  • Higher fuel consumption, sometimes accompanied by a cylinder 1 misfire code

Likely causes

  • Oil-soaked, corroded or loosely seated connector at the cylinder 1 oil supply solenoid
  • Chafed or heat-damaged wiring between the solenoid and the ECM, giving an open circuit or a short to ground
  • Open or internally shorted winding in the solenoid coil
  • High resistance in the supply feed or in the ground shared by the valve-train solenoids
  • Engine oil tracking across the connector terminals after a valve cover or camshaft seal leak
  • Failed output driver inside the ECM, considered only after the wiring and the solenoid test good

How to fix it

  1. Read the freeze frame first and note whether the fault appeared cold, hot or during vibration
  2. Scan for the companion oil supply solenoid codes; if every cylinder reports a fault, suspect the shared feed or ground rather than one solenoid
  3. Inspect the solenoid connector for oil ingress, spread terminals and green corrosion; clean and re-seat before replacing anything
  4. Measure the solenoid winding resistance and compare it with the other cylinders — a large deviation points to a failed coil
  5. Confirm battery voltage on the supply side with the ignition on and verify the ground path with a voltage-drop test
  6. Wiggle the harness along the cylinder head while watching an ohmmeter or live data to expose an intermittent break
  7. Replace the solenoid if it fails the resistance check, repair the damaged harness section, and only then consider the ECM driver

Codes From the Same System

All Fault Codes

Related Similar Codes

This information follows the generic OBD-II definition and does not replace a vehicle-specific diagnosis. The severity rating is rule-based; an authorised diagnostic reading is required for a definitive answer.