What Does P1261 Mean?
The ECM has detected a high-to-low side short circuit in the cylinder #1 fuel injector driver circuit. This means the high-side power feed and low-side ground control wires for the injector are making unintended contact, bypassing the ECM's injector driver transistor. This can cause the injector to fire uncontrollably or not at all, resulting in a misfire, rough running, or potential damage to the ECM driver circuit.
Safety Warning
A shorted injector circuit can cause a cylinder misfire resulting in rough running and loss of power. In severe cases, an uncontrolled injector can cause fuel wash on the cylinder wall leading to accelerated wear, or hydrolocking if fuel floods the cylinder. Additionally, the shorted circuit may damage the ECM driver, leading to a much more expensive repair.
Common Causes
35%
Damaged or chafed injector wiring harness with high and low side wires contacting each other
30%
Failed fuel injector with internal coil short circuit
20%
Corroded injector connector allowing cross-circuit leakage between pins
15%
ECM injector driver circuit failure
Diagnostic Steps
1
Identify which cylinder is #1 on your engine and locate its fuel injector connector.
2
Disconnect the cylinder #1 injector connector and check for corrosion, moisture, or contamination between the pins that could create a short path.
3
Measure the injector coil resistance (typically 11-18 ohms for high-impedance injectors). Also check for continuity between each injector terminal and the injector body — there should be no continuity.
4
With the injector disconnected, check for continuity between the two harness-side wires at the injector connector — there should be no continuity. If there is, trace and repair the shorted wiring.
5
If the injector and wiring test good, the ECM injector driver may be damaged. Swap injector connectors with an adjacent cylinder to see if the code follows the harness or the injector.
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 #1 fuel injector driver circuit. This means the high-side power feed and low-side ground control wires for the injector are making unintended contact, bypassing the ECM's injector driver transistor. This can cause the injector to ...
The most common cause of P1261 (Cylinder #1 High To Low Side Short) is: Damaged or chafed injector wiring harness with high and low side wires contacting each other
Typical repair costs for P1261 range from $100 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A shorted injector circuit can cause a cylinder misfire resulting in rough running and loss of power. In severe cases, an uncontrolled injector can cause fuel wash on the cylinder wall leading to accelerated wear, or hydrolocking if fuel floods the cylinder. Additionally, the shorted circuit may damage the ECM driver, leading to a much more expensive repair.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1261 to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Powertrain
System
Fuel Injection System
Difficulty
Type
Manufacturer
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
