U0295

Code

Generic U — Network/User

Lost Communication With AC/AC Converter Control Module

Brand: Generic

Type: U — Network/User

Views: UK: 30 EN: 43 RU: 26

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Page language: EN

Causes

Blown fuse or disabled power feed to the AC/AC Converter Control Module
Poor or corroded connector or pin at the module
Open, short or high-resistance CAN/data bus wiring between the module and vehicle network
Faulty module (failed CAN transceiver or internal electronics)
Missing or incorrect bus termination (resistor) or bus off condition
Battery or chassis ground problem affecting module reference

Symptoms

Related A/C converter or inverter functions inoperative or degraded
HVAC, charging or electric-drive subsystem faults (where applicable)
Malfunction Indicator Lamp (MIL) or warning lights illuminated
Loss of related system data on scan tool (module not present in network list)
Intermittent operation or complete loss of function from the controlled system

What to check

Obtain the complete freeze frame and network list with a capable scan tool; attempt to communicate with the AC/AC Converter Control Module
Check battery voltage and general power condition (12V nominal, >12V with engine off, >13V with engine running)
Inspect fuses and relays supplying the module; replace suspect fuses and retest communication
Visually inspect the module connector and wiring for corrosion, bent pins, damaged insulation, or recent repair/aftermarket splices
Check for other network U-codes or modules reporting bus problems (bus off, short, or intermittent)
Measure CAN bus idle voltages at a known-good module or at the AC module connector (see signal parameters)

Signal parameters

CAN High idle voltage ≈ 2.5 V (typically 2.5–3.5 V depending on vehicle)
CAN Low idle voltage ≈ 2.5 V (typically 1.5–2.5 V; differential idle ≈ 0 V)
Active CAN differential swing ≈ ±1 V (CANH ~3.5 V, CANL ~1.5 V during dominant bits)
Termination resistance between CANH and CANL ≈ 60 ohms (two 120 Ω in parallel)
Module supply voltage (pin) ≈ battery voltage (12–14.5 V), with key ON/run and during cranking
Module ground resistance to chassis < 1 ohm (preferably < 0.1–0.2 ohm)

Diagnostic algorithm

Retrieve freeze frame, full DTC list and network topology from the scan tool. Note any other network codes. Clear codes and attempt to re-communicate to verify persistence.
Verify battery voltage and condition. Recharge or connect a stable supply if battery is low. Re-scan after verifying power.
Check and verify all fuses and relays that supply the AC/AC Converter Control Module. Replace any blown fuse and retest communication.
Visually inspect the module connector and wiring harness for damage, corrosion, bent pins, loose terminals or aftermarket splices. Repair as required.
With ignition ON, measure module supply and ground pins for correct voltage and low resistance to chassis. Repair power/ground faults before further testing.
Using a lab scope or CAN bus tester, observe CANH and CANL at the module connector and at a known-good network node. Confirm idle voltages and presence of CAN activity. If bus is idle or shows bus-off levels, pursue wiring/termination faults.
Measure termination resistance between CANH and CANL with the key OFF. Expect ~60 ohms. If open or greatly different, locate broken termination or missing module providing termination.
Perform a wiggle test on wiring between the module and the gateway/ECU while monitoring communications to identify intermittent opens or shorts. Repair broken/chafed wiring.
If disconnecting the module restores network communications for other modules, suspect the module as the fault. If module is confirmed faulty and wiring/power/grounds are good, follow manufacturer procedure for module replacement and programming.
After repair or replacement, clear DTCs and perform a full system scan and road test (if applicable) to confirm the fault does not return. Document findings and repairs.