Network, generic (extended)

U3015 Control Module Ground C

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U3015 reports that the third ground path of a module, labelled C, is missing or no longer plausible. Three or four separate grounds are found mainly on units that drive heavy loads, such as brake, steering or power distribution modules, where control electronics and power stages return current through their own wires. No manufacturer documents U3015 publicly. The published logic for grounds A and B gives the pattern: GM's 19OBDG03B brake module compares the voltages on two grounds and flags one as lost once the ratio leaves ±0.9, and Ford's 26-2150 ties each ground letter to a specific body point. Which pin is C is defined only by that module's wiring diagram. A failing ground C can bring warning lamps, a disabled function or erratic readings from the same module.

Likely causes

Corroded or loose ground eyelet at the body or frame point
Chafed or broken ground wire between module and ground point
Spread or corroded ground pin in the module connector
Internal fault in the module's ground measurement

Symptoms

  • Warning lamp or message for the system run by the affected module
  • Function cut back or switched off, often depending on load or moisture
  • Stored together with other supply or ground codes of the same module

Repair estimate

DifficultyMediumDIY possible
Parts and labour€10–250
Time0.5–2 h

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

Parts involved

module ground cground strap

Related codes

U3016U3008U3009U3013

References: law.cornell.edu, gsi.ext.gm.com, static.nhtsa.gov.