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Home / DTC / U01AC — Lost Communication With Hybrid/EV Battery Interface Control Module M

U01AC — Lost Communication With Hybrid/EV Battery Interface Control Module M

Detailed page for trouble code U01AC.

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Code

U01AC

Generic U — Network/User

Lost Communication With Hybrid/EV Battery Interface Control Module M

Brand: Generic
Type: U — Network/User
Views: UK: 13 EN: 19 RU: 19
AI status
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Page language: EN

Causes

  • Open or shorted wiring on the communication bus (CAN/LIN/FlexRay) between modules
  • Loss of module power or ground (blown fuse, disconnected pigtail, poor ground)
  • Failed CAN/LIN transceiver or module internal failure
  • Corroded or loose connector at battery interface module or gateway module
  • Missing or incorrect bus termination or bus short to battery/ground
  • Intermittent connection caused by vibration or damaged insulation

Symptoms

  • MIL / warning lamp illuminated and a U01AC stored
  • Hybrid/EV system disabled or limited (no EV mode, reduced power, no regen)
  • Battery state/fuel gauge or hybrid system messages missing or incorrect on cluster
  • Starting or charging restrictions for hybrid/EV functions
  • Other network modules reporting related communication U-codes

What to check

  • Read all stored and pending U- and P-codes and note freeze-frame data
  • Check for related codes on gateway, powertrain and battery management modules
  • Visual inspection of wiring and connectors at battery interface module and gateway
  • Verify module supply voltage and ground with ignition ON (check fuses and relays)
  • Backprobe CANH and CANL at the module and gateway to verify idle voltages and activity
  • Measure termination resistance across CANH–CANL (nominal ≈ 60 Ω for two 120 Ω terminators in parallel)

Signal parameters

  • Module battery/supply voltage: ≈ 12 V (key ON) or as specified by OEM
  • Ground continuity: near 0 Ω to vehicle chassis (< 1–2 Ω preferred)
  • CAN bus recessive voltages: CANH ≈ 2.5 V, CANL ≈ 2.5 V (verify with scope/multimeter per OEM spec)
  • CAN dominant voltages: CANH ≈ 3.5–4.0 V, CANL ≈ 1.0–1.5 V (on active frames)
  • Differential voltage on active frames: ≈ 1.5–3.0 V (dependent on bus speed and transceivers)
  • Termination resistance CANH–CANL: ≈ 60 Ω (verify per vehicle specification)

Diagnostic algorithm

  1. Retrieve live data and all U/P codes with a capable scan tool; record freeze-frame and module presence.
  2. Note whether the battery interface module responds to the scanner. If it does not respond, confirm other modules on the same bus do respond.
  3. Visually inspect connectors and wiring at the battery interface module, gateway and any intermediate splice points; repair any corrosion or damage.
  4. Verify module supply and ground: check fuses, relays and measure voltage at the module supply pin with ignition ON. Repair fuse/relay faults or wiring issues.
  5. Backprobe or access the CANH/CANL pins at the module and gateway. With ignition ON, observe idle voltages and look for data activity using a scope or CAN bus analyzer.
  6. Measure termination resistance across CANH–CANL with the network unpowered. Replace missing or damaged terminations to obtain nominal resistance.
  7. If one end of the bus fails or shows a short, isolate sections by disconnecting connectors/modules one at a time to find the faulted segment (avoid disconnecting high-voltage components unless qualified).
  8. If wiring and power/ground are good but no communication, suspect internal transceiver or module failure. Verify with manufacturer test procedures; consider reflashing software if available.
  9. Review technical service bulletins and wiring diagrams for unique architecture (gateway, CAN FD, multiple subnets) before module replacement.
  10. Replace the battery interface control module only after confirming wiring, power/ground, and bus integrity; program/configure the replacement per OEM requirements.

Likely causes

  • Blown/loose ignition or module supply fuse feeding the battery interface module
  • Corroded/damaged connector at the battery interface control module
  • Open/shorted CANH or CANL wiring (pin damage, chafing, water intrusion)
  • Faulty CAN transceiver inside the battery interface module or gateway module
  • Vehicle gateway or powertrain control module not bridging the network correctly

Fault status

⚠️ Status
Lost Communication With Hybrid/EV Battery Interface Control Module M — module not responding on vehicle network (communication timeout or bus silence).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0100 U0121 U0140 U0293 U0415
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