Network, generic (extended)

U3027 Control Module A Disable Circuit High

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U3027 is the high-side counterpart: the disable line to module A reads above its valid range, as with a short to battery voltage or a neighbouring wire. In an active-low design such as the one in Siemens patent US7596436B2, where pulling the shutdown path to ground blocks the output stages, a line stuck high means module A keeps its enable and can no longer be switched off over the hard-wired path. That removes the independent safety layer FCA's patent US10676100B2 is built around, where losing a shutoff line could let a hybrid keep producing torque. Systems therefore treat this case strictly and usually disable the function by other means. No manufacturer documents U3027 publicly; check for a short to a powered wire in the harness and for water in connectors.

Likely causes

Disable wire shorted to a battery or supply wire
Moisture or corrosion bridging pins in a connector
Output driver of the supervising module stuck high

Symptoms

  • Function locked out by the safety concept, system warning shown
  • Vehicle may not become ready to drive

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

U3025U3026U302AP2C98

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