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Home / DTC / U301A — Control Module Wake-up Circuit A/Open

U301A — Control Module Wake-up Circuit A/Open

Detailed page for trouble code U301A.

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Code

U301A

Generic U — Network/User

Control Module Wake-up Circuit A/Open

Brand: Generic
Type: U — Network/User
Views: UK: 14 EN: 12 RU: 11
AI status
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Page language: EN

Causes

  • Open or damaged wake-up wiring (broken conductor, chafing, or connector separation)
  • Corroded, bent, or pushed-out connector pins
  • Blown or open fuse supplying the wake or related power/ignition feed
  • Faulty ground at the module or intermediate ground strap
  • Body/BCM/gateway not sending wake signal (upstream module fault or software issue)
  • Intermittent connection from aftermarket device (alarm, immobilizer, telematics)

Symptoms

  • No communication with the control module on scan tool or delayed response
  • Features controlled by the module not available until ignition cycle or never
  • Reduced vehicle functionality (e.g., convenience, telematics, vehicle subsystem inactive)
  • Possible repeated wake faults or wake-related warning lights
  • Module stays asleep leading to no response to commands

What to check

  • Verify and record battery voltage and state of charge before testing
  • Use a scan tool: confirm U301A is set, check freeze frame and related codes
  • Visual inspection of wiring harness and module connector for damage, corrosion, bent pins
  • Check relevant fuses and relays for continuity and correct operation
  • Backprobe the wake-up input pin at the module connector while commanding wake from a scan tool
  • Wiggle harness and connector while monitoring voltage/communication to reproduce intermittent faults

Signal parameters

  • Idle (module asleep): wake input may be steady low or at defined logic level — expected behavior is vehicle-specific
  • Active (commanded wake): wake line typically shows a voltage transition or pulses (logic-level ~5V or battery-level pulses ~9–14V depending on design)
  • Continuity: wiring harness should show low resistance; open/infinite resistance indicates break
  • CAN/LIN wake frames: network traffic should appear on bus when wake is commanded — use scope or CAN logger to verify
  • If no transition or pulses when wake commanded, the wake circuit is effectively open

Diagnostic algorithm

  1. Read and record U301A and any related DTCs with a capable scan tool. Note freeze frame and occurrence conditions.
  2. Verify battery and main power rails are within specification. Low battery can prevent wake sequences and cause misleading results.
  3. Inspect visually: connector at affected module, wiring harness for damage, pin corrosion, and secure mating.
  4. Check fuses/relays that feed the module and wake circuits; replace any blown fuses and retest.
  5. With ignition off, measure resistance/continuity between the module wake pin and the upstream source (BCM/gateway) or fuse; an open indicates wiring/connector fault.
  6. Backprobe wake input at the module. Command a wake from the scan tool or perform a door/ignition action that should wake the module and observe voltage or pulses with a DMM/oscilloscope.
  7. If no signal at the module but present at the upstream device, inspect/repair harness between them (splice, connector, intermediate junction).
  8. If wake signal is present at the module connector but code persists, suspect internal module input failure — try re-seating connector, clearing codes, and retesting.
  9. Check for and remove aftermarket devices that may interrupt wake circuit and retest.
  10. If available and safe, substitute a known-good module or have module bench-tested by a qualified service provider before module replacement.
  11. After repair, clear codes, perform full sleep/wake cycles and verify normal communication and absence of U301A.

Likely causes

  • Broken wire in harness between gateway/BCM and affected control module
  • Poor connector contact or corrosion at module connector
  • Open fuse or relay in wake/power feed circuit
  • Upstream module (BCM/gateway) not issuing wake due to its fault or configuration
  • Module internal input transistor/circuit failure

Fault status

⚠️ Status
Control Module Wake-up Circuit A/Open — the module reports no valid wake signal on its wake input. Module may remain asleep and not communicate until the circuit is repaired.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0100 U0121 U0155 U3000 U0301
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