What it means
Voltage on the malfunction indicator lamp control line is below the expected window. Usually a short to ground or a shorted bulb driver.
At a glance
- Usually lights the check-engine light
How it works
The malfunction indicator lamp (MIL), commonly called the check-engine light, is controlled through an electrical driver circuit. P263A sets when the control line voltage is lower than expected, consistent with a control wire shorted to ground, a shorted lamp driver, or a poor connector connection.
Common causes
Most likely first.
- Control wire shorted to ground
- Bulb driver internally shorted
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light does not illuminate during key-on bulb check
- MIL may not illuminate when another fault occurs
How to diagnose it
- Turn the ignition on and observe whether the check-engine light illuminates during the bulb check, since a low control circuit may leave the MIL dark.
- Scan for other faults and confirm whether the vehicle can command the MIL on, if that function is available in the scan tool.
- Inspect the MIL control wire and its connectors for chafing to ground, corrosion, loose pins, or signs of a shorted driver.
- With the wiring diagram, check the control line for an unwanted short to ground and test connector continuity using the manufacturer's procedure.
- If the wiring and connections are sound, test the lamp driver or module output according to the vehicle's diagnostic information.
Common fixes
- Repair a control wire rubbed through and shorted to ground.
- Clean, tighten, or repair corroded MIL circuit connector pins.
- Repair or replace a confirmed shorted bulb driver.
- Replace a faulty control module only after its wiring and output circuit are verified.
Can I keep driving?
The MIL may fail to warn you when another engine or emissions fault occurs, even if the vehicle seems normal. Arrange diagnosis promptly and watch for other warning lights or changes in how the engine runs.
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.