Network, generic

U067D Lost Communication With Fan 4

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modePossible

U067D is meant for a fourth cooling fan with its own network interface that has stopped answering. Four electrically commanded fans are rare. No manufacturer documents U067D publicly: GM's 2025 diesel table 25OBDG04B ends at fan 3, and the engines in GM's 23OBDG07 and 24OBDG07, which do have a fourth LIN fan, report it with the GM-specific code U112B once its response frame ECM_LIN3_CFM4_RSP has been missed three times, maturing over two trips. LIN suits such small motor nodes, and cooling fan motors are a classic application. If fan 4 is wired conventionally, its faults appear as P2C3E to P2C40 for the control circuit and P2C42 for performance. Losing one of four fans mostly shows when cooling demand is high.

Likely causes

Bus wire to fan 4 damaged

Fan 4 power feed or ground interrupted

Fan 4 electronics or motor failed

Symptoms

Temperature climbs in traffic or under heavy load
Warning light depending on manufacturer
Fan 4 does not run

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€60–800

Time0.5–3 h

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

Parts involved

cooling fan 4vehicle bus wiring

References: gsi.ext.gm.com, gsi.ext.gm.com, en.wikipedia.org.