P1261 - High to Low Side Short in Cylinder #1 Injector Circuit
Code P1261 indicates an electrical short between the high-side and low-side circuits of the fuel injector for cylinder #1. This typically occurs when the injector coil fails internally, causing a direct short, or when wiring insulation is damaged, allowing the two circuits to touch. The engine control module (ECM) detects an abnormal current flow and sets the code, often disabling the injector to prevent further damage.
1. Symptoms You Will Notice
- Misfire on cylinder #1
- Rough idle or engine shaking
- Check Engine Light illuminated
- Reduced fuel economy and power
2. Most Common Causes
- Faulty or internally worn accelerator pedal position (APP) sensor
- APP sensor circuit wiring shorted to ground, battery, or open circuit
- Loose, corroded, or damaged terminals in APP sensor connectors
- Internal PCM failure in the analog-to-digital conversion channels (rare)
- Electromagnetic interference (EMI) in the sensor harness
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect injector #1 wiring and connector for damage or corrosion.
Step 3: Measure resistance between high-side and low-side pins at injector connector; should be infinite (open) – a low reading indicates a short.
Step 4: Swap injector #1 with another cylinder and clear codes; if the code moves, replace the injector.
Step 5: If wiring is damaged, repair or replace the harness section.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
No, driving with a shorted injector can cause misfire, catalytic converter damage, and potential fire risk. Have it diagnosed and repaired promptly.
How much does it cost to fix?▼
Replacing a single fuel injector typically costs $150-$400 including parts and labor. Wiring repairs may be less expensive.
5. Commonly Affected Makes
This is a manufacturer-specific code. The exact manufacturer is not confirmed in our current database.