What it means
Voltage on the malfunction indicator lamp control line is above the expected window. Typical causes are a short to battery or an open lamp.
At a glance
- Usually lights the check-engine light
How it works
The malfunction indicator lamp (MIL), or check-engine light, is operated by a control circuit that switches the lamp as commanded. P263B sets when voltage on that circuit is higher than expected, which can result from a short to battery voltage, an open lamp path, or a poor connector connection.
Common causes
Most likely first.
- Control wire shorted to B+
- Burnt-out MIL bulb
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light stays illuminated when it should be off
- MIL may not respond correctly during the key-on bulb check
How to diagnose it
- Check whether the MIL stays on or fails its key-on bulb check, and record any other warning lights or stored codes.
- Use a scan tool to command the MIL on and off if the vehicle supports that function, then compare the response with the observed lamp.
- Inspect the MIL bulb or indicator, control wiring, and connectors for an open circuit, corrosion, loose pins, or contact with battery-voltage wiring.
- Use the wiring diagram and manufacturer's procedure to test for an open in the lamp path or a short to battery voltage.
- If the wiring and lamp are sound, test the controlling module's output circuit before considering module replacement.
Common fixes
- Replace a confirmed burnt-out MIL bulb or repair an open lamp connection.
- Repair wiring shorted to battery voltage.
- Clean and secure corroded or loose connector pins in the MIL circuit.
- Repair a faulty driver or replace a control module only after circuit testing confirms the cause.
Can I keep driving?
Because the check-engine light may remain on or fail to respond correctly, you may not be able to tell whether a separate engine fault has appeared. Avoid ignoring new symptoms or warnings and have the circuit checked soon.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.