P263BMIL Control Circuit High
- Generic OBD-II code · Powertrain
- Matters for the ITP
- How the car detects it
- P263B is stored when the MIL control line is stuck at supply voltage while the module has switched its driver on to light the lamp. GM treats an impedance toward power of about 0.5 ohm as the fault and needs 4 failures within 5 samples, each 50 ms apart, provided run/crank voltage is at least 11 V and no remote start is running. As with P263A, GM labels the code Type B with no MIL, because a shorted control circuit cannot reliably show the warning. In practice the indicator stays dark even when other emissions faults are present, which is why reading stored codes matters, also before an emissions inspection. GM's PIT5391 bulletin ties P263B on 2014–2016 full-size trucks and SUVs to a missing ignition 1 supply. Check the cluster wiring and the driver output.
- What you may notice
- Engine warning lamp does not light, not even at key-on bulb check
- Other emissions codes stored without warning
- Likely causes
- LikelyMIL control wire shorted to a positive feed
- PossibleIgnition 1 supply interrupted at relay or fuse block
- RareLamp driver in the engine module failed
- Inspection (ITP)
- Can matter for the ITP: it concerns the emissions system.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €40 – €500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.