U3029 Control Module A Disable Feedback Circuit Low

U3029 narrows the feedback fault to a signal that stays below its valid range, typically a readback wire shorted to ground. The consequence follows from the readback idea in GM's patent US9122662B2, where the inhibit path is driven through known test states and its actual output compared with the expected one: if the feedback is pinned low, every state that should read high fails, and the monitor cannot tell a working shutdown from a broken one. Depending on the design, a permanently low readback may also be taken as module A already being disabled. No manufacturer documents U3029 publicly. The usual suspects are a chafed readback wire touching the body, water in a connector or a defective input stage; the disable line itself should be checked separately.

Likely causes

Symptoms

• Function of module A locked out, system warning displayed
• Code returns at every start until the short is found

Repair estimate

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

Parts involved

Related codes

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