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P1560

Back-Up Voltage Circuit Malfunction.

  • Subaru
  • Powertrain
  • Manufacturer code
  • Medium severity

How this code is built

P
SystemPowertrain
1
Defined byThe manufacturer
5
AreaVehicle speed, idle control and auxiliary inputs
60
FaultThe specific fault in that area

What it means

On a Subaru, P1560 means the engine control unit has detected a fault in the back-up voltage circuit. This is the constant battery feed that keeps the control unit's memory alive (learned values, fault codes and adaptations) when the ignition is switched off. The control unit saw the permanent supply missing, too low or unstable, so the code is set.

Symptoms

  • Check engine light on
  • Engine cranks but starts poorly or takes longer than normal to start
  • Erratic or reset idle after the battery has been disconnected or has gone flat
  • Stored fault codes or learned values lost after switching off
  • Other warning lights or intermittent electrical faults
  • Radio or clock settings lost on some cars

Possible causes

  • Weak, flat or poorly connected battery, or loose or corroded battery terminalslikely
  • Blown or loose fuse in the permanent battery feed to the engine control unitlikely
  • Damaged, corroded or loose wiring or connector on the back-up supply to the engine control unitpossible
  • Poor engine control unit earth connectionpossible
  • Recent battery disconnection or jump start causing a voltage dip that set the codepossible
  • Internal fault in the engine control unitrare

How to diagnose

  1. Read all stored codes and freeze frame data, note whether the code is current or history, and check for any other voltage or battery-related codes
  2. Ask about recent battery disconnection, replacement, jump starting or a flat battery
  3. Inspect the battery terminals and clamps for corrosion and tightness
  4. Test the battery state of charge and condition, and check the charging system output with a multimeter
  5. Check the fuses in the permanent feed circuit to the engine control unit, using the wiring diagram for the specific model and engine
  6. Inspect the engine control unit connector and the wiring to it for damage, water ingress, corrosion or pushed-back pins
  7. Measure the voltage at the control unit's permanent supply pin with the ignition off, and check the earth connections for voltage drop
  8. Clear the code, test drive and recheck to see if it returns

How to fix

  • Clean and tighten the battery terminals, or replace damaged clamps
  • Recharge or replace the battery if it fails testing, and repair any charging system fault
  • Replace any blown fuse once the cause of the failure has been found
  • Repair or replace damaged wiring or connector terminals on the back-up supply or earth
  • Clean and refit the engine control unit earth connections
  • Replace or reprogram the engine control unit only after all supply and earth faults are ruled out, and following the manufacturer's procedure

Can I keep driving?

Medium severity

The car can usually be driven short-term, but a lost or unstable supply can cause hard starting or a no-start, so get it checked soon. If the car stalls, starts badly or shows other warnings, limit driving.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.

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