P1277: Cylinder #7 Injector Circuit Open
Code P1277 indicates an open circuit between the high and low sides of the fuel injector for cylinder #7. This typically means the injector coil has failed (open winding) or there is a wiring issue (broken wire, poor connector pin contact) between the injector and the engine control module (ECM). The ECM detects a lack of current flow when it attempts to fire the injector, setting the code. This can cause a misfire, rough idle, and reduced power.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Engine misfire on cylinder #7
- Rough idle, hesitation, or loss of power
- Increased fuel consumption and possible emissions failure
2. Most Common Causes
- Faulty fuel injector on cylinder #7 (open coil)
- Broken or corroded wiring in the injector circuit
- Loose or damaged connector at the injector or ECM
- ECM internal fault (rare)
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data. Clear code and test drive to confirm reoccurrence.
Step 2: Visually inspect injector #7 connector and wiring for damage, corrosion, or loose pins.
Step 3: Use a multimeter to measure resistance across injector #7 terminals (should be 11-17 ohms). If open (OL), replace injector.
Step 4: If injector resistance is good, check for 12V at injector connector with key on, and verify ground pulse from ECM using a noid light or oscilloscope.
Step 5: If wiring and injector are good, suspect ECM failure; test by swapping injector with another cylinder to see if code moves.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. Driving with a misfire can damage the catalytic converter and cause poor performance. Have it diagnosed promptly.
How much does it cost to fix?▼
Replacing a single fuel injector typically costs $150-$400 including parts and labor. If wiring repair is needed, it may be less.
5. Commonly Affected Makes
This is a manufacturer-specific code. The exact manufacturer is not confirmed in our current database.