Network, generic (extended)

U3026 Control Module A Disable Circuit Low

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U3026 is logged when the disable line to module A sits below its valid voltage range, typically because it is shorted to ground. What that means depends on the polarity the maker chose. In the Siemens control unit of patent US7596436B2 the enable signal is high for run and low for shutdown, and a monitoring circuit cuts the output stages by pulling the shutdown paths to vehicle ground. With such active-low logic a short to ground looks exactly like a permanent shutdown command, so module A stays off and the driver loses that function, although nothing else is wrong. Where low is the run state, the danger is the opposite, since the shutdown can no longer be signalled. No manufacturer documents U3026 publicly. Look for a chafed wire touching the body between the two modules.

Likely causes

Disable wire chafed through and touching body ground
Moisture in a connector creating a leak path to ground
Supervising module holding the line low permanently

Symptoms

  • Module A stays switched off, function unavailable
  • Warning message for the affected system

Repair estimate

DifficultyHardWorkshop job
Parts and labour€50–1,200
Time1–4 h

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

Parts involved

module disable acontrol wiring

Related codes

U3025U3027U3029P2C97

References: law.cornell.edu, patents.google.com, patents.google.com.