P263B code meaning
MIL Control Circuit High
What P263B means
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.
P263B at a glance
- Check engine lightUsually not
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P263B
- Engine warning lamp does not light, not even at key-on bulb check
- Other emissions codes stored without warning
Common causes of P263B
- Most likelyMIL control wire shorted to a positive feed
- PossibleIgnition 1 supply interrupted at relay or fuse block
- Less likelyLamp driver in the engine module failed
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
MIL lampInstrument clusterWiring harness
What each part of P263B means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 6 | Area: computer (engine control module) and output circuits. |
| 3B | The exact fault in that area. |
What to do next
- Note P263B and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P263B
What does P263B mean?
P263B means "MIL Control Circuit High". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P263B?
P263B does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P263B fail an emissions test?
Yes, it can. P263B is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P263B to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. This is a job for a workshop.
Will P263B clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.