What Does P1263 Mean?
The ECM has detected a high-to-low side short circuit in the cylinder #3 fuel injector driver circuit. This short between the power supply and ground control sides of the injector circuit prevents proper ECM-controlled fuel injection for cylinder #3. The engine will experience a misfire on this cylinder with rough running and reduced performance.
Safety Warning
Continuous cylinder #3 misfire causes loss of power and rough running. Unburned fuel can overheat and damage the catalytic converter. Potential for ECM driver damage if the short circuit is not resolved. Extended operation with a dead cylinder increases stress on remaining cylinders.
Common Causes
35%
Wiring harness damage with injector high and low side conductors contacting each other
30%
Internal short circuit in the cylinder #3 fuel injector coil
20%
Moisture or corrosion in the cylinder #3 injector electrical connector
15%
ECM injector driver transistor failure for cylinder #3
Diagnostic Steps
1
Scan for additional injector circuit codes and misfire codes (P0303) to assess whether the problem is isolated to cylinder #3.
2
Disconnect the cylinder #3 injector and visually inspect the connector for signs of heat damage, corrosion, or coolant contamination.
3
Measure the injector resistance — should be within specification. Also verify no continuity exists between either injector terminal and the injector housing/ground.
4
Check the harness side of the connector for continuity between the two wires with the injector disconnected — continuity indicates a wiring short.
5
Perform an injector swap test with a known-good cylinder. Clear codes and run the engine to determine if the fault follows the injector or stays with the cylinder #3 harness.
Estimated Repair Cost
$100 - $500
Parts + labor, varies by vehicle and location
The ECM has detected a high-to-low side short circuit in the cylinder #3 fuel injector driver circuit. This short between the power supply and ground control sides of the injector circuit prevents proper ECM-controlled fuel injection for cylinder #3. The engine will experience a misfire on this cyli...
The most common cause of P1263 (Cylinder #3 High To Low Side Short) is: Wiring harness damage with injector high and low side conductors contacting each other
Typical repair costs for P1263 range from $100 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Continuous cylinder #3 misfire causes loss of power and rough running. Unburned fuel can overheat and damage the catalytic converter. Potential for ECM driver damage if the short circuit is not resolved. Extended operation with a dead cylinder increases stress on remaining cylinders.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1263 to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel Injection System
Difficulty
Type
Manufacturer
Recommended Tools
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