Powertrain, generic · Vehicle speed, idle control and auxiliary inputs

P05C7 Economy Mode Switch Circuit/Open

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

The economy mode switch selects a fuel-saving mode (flatter pedal map, earlier upshifts, sometimes reduced A/C). It is usually a resistor ladder with 5 V reference read by the engine module; CARB names a driver-selectable eco mode as an off-cycle technology whose use must be counted. GM reports the same switch with its own codes P159F/P15A0, type B with warning lamp after two trips; P05C7–P05CA appear in no manufacturer document available to us. P05C7 means the switch circuit is open; eco mode cannot be selected and the vehicle runs in normal mode.

Likely causes

Wire or connector to the switch open
Switch faulty (resistor ladder or contact)
Connector loose after console work
Module input

Symptoms

  • Eco mode not selectable
  • Eco indicator not working
  • Vehicle runs in normal mode

Repair estimate

DifficultyEasyDIY possible
Parts and labour€30–200
Time0.3–1.5 h

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

Parts involved

economy mode switchswitch wiringengine control module

Related codes

P05C8P05C9P05CAP05BC

References: saabwisonline.com, law.cornell.edu.