U300DIgnition Input On/Start
- Generic OBD-II code · Network
- How the car detects it
- U300D concerns the line that should be live in On and Start only, which GM calls Run/Crank Ignition 1; in GM's 2012 truck wiring manual it is active in run and crank and inactive in off and accessory. A module sets the code when this line and the power mode on the bus disagree. GM's PIT5817A for 2020–2021 Envision, CT4, CT5, Escalade, Corvette, Tahoe, Suburban and Yukon shows the typical case: the instrument cluster stores U300D while the ECM, TCM and brake module log P2535, often after remote start, and the customer finds a dead battery and a service engine lamp. The BCM's driver for the ignition main relay stays on after key-off and keeps circuit 5199 powered, so the line remains live with the car off; the fix is a new BCM. The cluster's code itself is the witness, not the cause.
- What you may notice
- Battery repeatedly discharged after the car was parked
- Service engine lamp at start-up with P2535 in other modules
- Cluster or other modules staying awake with the ignition off
- Likely causes
- LikelyBody control module keeping the run/crank relay energized after key-off
- PossibleRun/crank relay sticking closed or failing to close
- PossibleBlown fuse or open wire in the run/crank feed to the module
- RareBackfeed from an aftermarket device tapped into the run/crank circuit
- Repair
- Medium · Usually a job for a workshop.Typical cost: €20 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.