U302F

Code

Generic U — Network/User

Ignition Output Accessory

Brand: Generic

Type: U — Network/User

Views: UK: 25 EN: 24 RU: 27

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Blown fuse protecting the accessory/ignition output circuit
Faulty ignition switch or accessory position contact
Defective ignition/accessory relay or relay driver
Open, short to ground, or short to battery in the harness to the accessory output
Poor or corroded connector or ground at the module or accessory distribution point
Module internal fault (BCM/IPC/PCM) or software anomaly

Symptoms

Accessories (radio, power outlets, HVAC blower, etc.) not powered in ACC or ON position
Intermittent or no response from accessory circuits when key is turned to ACC/ON
Related warning lamps or network communication warnings
Difficulty starting or ignition position not recognized by modules
Diagnostic trouble codes related to other modules or bus loss

What to check

Read and record the DTC and any related codes/freeze frame with a capable scan tool
Verify correct battery voltage and state of charge
Inspect fuses and fuse holders for the accessory/ignition circuits
Check operation of ignition switch through its key positions
Verify relay presence and operation for ignition/accessory feed
Visually inspect connectors and wiring for damage, corrosion or loose pins

Signal parameters

Accessory/Ignition output: battery voltage (~11–14.5 V) when key in ACC/ON; ≈0 V when key OFF
Switching: output should change state immediately when ignition key changes position
Current capability: limited by fuse/relay rating – expected to supply accessory load without voltage collapse
Module status: status message/bit indicating ignition/accessory state sent over vehicle bus when equipped
Expected behavior: no unexpected high resistance, no sustained short to ground or battery

Diagnostic algorithm

Connect a scan tool, verify U302F is current/historic; record freeze frame and any related codes. Attempt to reproduce the fault by cycling key to ACC/ON.
Verify battery voltage is within nominal range. Low voltage can cause false reports—charge or replace battery as needed.
Visually inspect fuses and fuse holders for the accessory/ignition circuit. Replace any blown fuses and retest.
Locate and test ignition/accessory relay (if fitted). Swap with a known-good relay of same type or bench-test relay continuity and coil resistance.
With key in ACC/ON, measure voltage at the accessory/ignition output terminal(s) and at accessory feed points. Voltage should be near battery voltage. If not present, trace back toward relay/switch/module.
Check wiring continuity from the module or relay output to the accessory distribution point. Look for opens, shorts to ground or battery, and high-resistance connections.
Inspect and measure module ground points and power supply pins. Repair poor grounds or corroded terminals.
Test ignition switch function and continuity across switch positions if measurements indicate switch-related failure.
If wiring, switch, fuse and relay are good, verify module communication on the vehicle bus. Check for other U-codes or communication errors that could indicate a module fault.
If module hardware or software is suspected, check for available technical service bulletins or programming updates. Reprogram or replace the module only after confirming circuitry and communications are good and following manufacturer procedures.
After repairs, clear the code and road-test to confirm the output is stable and the DTC does not return.