OBD Guide
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P05C9

Economy Mode Switch Circuit Low

P05C9 is an OBD-II diagnostic trouble code meaning: Economy Mode Switch Circuit Low. Common causes: short circuit of the signal wire of the switch to ground, loss of reference voltage due to broken power wire. Estimated repair cost: $11–78.

Severity
✅ Low
Can you drive?
Do not drive — repair immediately
Approx. repair cost
$11–78 (est.)

Symptoms

  • Check Engine light is on
  • Economy mode is not activated
  • Eco Mode button does not function
  • No Eco indicator on the dashboard
  • Possible slight increase in fuel consumption

Causes

  • Short circuit of the signal wire of the switch to ground
  • Loss of reference voltage due to broken power wire
  • Internal closure of the switch (contacts are shorted to the body)
  • Oxidation of connector contacts, creating a parasitic path to ground
  • Damage to the wiring in the harness (chafing at the corrugation or fasteners)

How to Fix

  1. Read all fault codes with a diagnostic scanner
  2. Find the Eco Mode switch and inspect its connector for damage
  3. Disconnect the switch connector and measure the reference power voltage - if it is absent, look for a break in the power wire
  4. If there is a reference voltage: measure the resistance between the signal wire and ground with the sensor disconnected - a short circuit will indicate damage to the wiring
  5. Inspect the wiring harness in the area to the switch, especially in places of kinks
  6. Replace the switch or repair the damaged wire

Related codes

P05C7P05C8P05CA

Error P05C9 by Vehicle Brand

AcuraAudiBAICBMWBYDBuickCadillacChanganCheryChevroletChryslerCitroenDodgeDongfengExeedFAWFordForthingFotonGACGMGMCGeelyGreat WallHavalHondaHongqiHyundaiInfinitiJACJaecooJaguarJeepJetourKaiyiKiaLadaLexusLi AutoLifanLincolnLivanMazdaMercedes-BenzMercuryMitsubishiNIONissanOldsmobileOmodaOpelPeugeotPlymouthPontiacRenaultSWMSaturnSkodaSkywellSubaruSuzukiTankToyotaVolkswagenVolvoVoyahXPengZeekrZotye

FAQ

What does the P05C9 code mean?

P05C9 is an OBD-II diagnostic trouble code that indicates: Economy Mode Switch Circuit Low

What causes a P05C9 error code?

The most common causes of P05C9 include: Short circuit of the signal wire of the switch to ground; Loss of reference voltage due to broken power wire; Internal closure of the switch (contacts are shorted to the body); Oxidation of connector contacts, creating a parasitic path to ground.

How do I fix a P05C9 diagnostic trouble code?

To fix P05C9: Read all fault codes with a diagnostic scanner. Find the Eco Mode switch and inspect its connector for damage. Disconnect the switch connector and measure the reference power voltage - if it is absent, look for a break in the power wire. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with P05C9?

Do not drive — repair immediately

How much does it cost to fix P05C9?

The estimated repair cost for P05C9 is $11–78. Actual cost depends on your vehicle, location, and labor rates.

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