U3022

Code

Generic U — Network/User

Ignition Input Accessory/Off

Brand: Generic

Type: U — Network/User

Views: UK: 21 EN: 27 RU: 19

AI status

Completed

ready

Completed 100%

Page language: EN

Accessory functions operate incorrectly (radio, windows, etc.)
Vehicle modules report incorrect ignition position on scan tool (OFF vs ACC/IGN)
Failure to enter expected key-off or accessory behavior
Parasitic battery drain when vehicle should be OFF
Intermittent starting or accessory power loss
Communications-related DTCs present (other U-codes)

Connect a full-function scan tool and read all stored/pending U-codes and related subsystem codes
Compare ignition position/status reported by multiple modules (BCM, IPC, ECM) using live data
Record freeze-frame and data when DTC sets; note battery voltage and timestamps
Check battery voltage and main ground connections (clean, tight)
Verify fuses and accessory relay operation for ignition/ACC circuits
Inspect ignition switch harness and connectors for damage, corrosion, or poor terminals

Ignition switch position signal (voltage levels for OFF, ACC, RUN, START)
Accessory relay control voltage (12V when active)
Battery voltage and transient voltage during key cycle (should be stable)
CAN or LIN message carrying ignition status (message present, correct frequency, CRC)
Node(s) reporting ignition state (BCM, IPC, ECM) — compare values and timestamps
Bus error counters (CAN Rx/Tx errors, bus-off counts)

Step 1: Retrieve all DTCs and freeze frame data with a scan tool; note other U-codes and related modules.
Step 2: Verify battery state of charge and main ground integrity; correct any low voltage or poor grounds.
Step 3: Use live data to monitor ignition position reported by each module while cycling key through OFF → ACC → ON → START; identify modules that disagree.
Step 4: Inspect fuses, accessory relay, and ignition switch connector for continuity and proper operation; replace or repair as needed.
Step 5: Check wiring harness from ignition switch to BCM/ignition module for opens/shorts/corrosion; perform backprobe voltage checks during key cycles.
Step 6: Scan CAN/LIN bus for communication errors; repair physical bus issues (loose terminator, damaged wires) if present.
Step 7: If wiring and bus are good but a specific module reports incorrect status, attempt module reset and clear codes; confirm whether fault returns.
Step 8: Check for relevant technical service bulletins or software updates; reflash or reprogram modules if prescribed by manufacturer.
Step 9: Replace suspected faulty module (ignition switch, BCM, IPC) only after confirming failure with bench/verifying tests and re-test system to ensure DTC does not return.

Damaged ignition switch common/ACC contact
Loose connector at ignition switch or BCM
Intermittent CAN/LIN transceiver fault in BCM or affected module
Failed accessory relay or open fuse in accessory feed
Missing/wrong software calibration or recent module update caused state mismatch