Cylinder #8 Injector Circuit Open
Code P1278 indicates an open circuit between the high and low sides of the fuel injector for cylinder #8. This means the injector's electrical circuit is incomplete, preventing the injector from opening. The ECM detects this by monitoring the voltage drop when the injector is commanded on. An open circuit can be caused by a faulty injector, damaged wiring, or a poor connection at the injector or ECM.
1. Symptoms You Will Notice
- Misfire on cylinder #8
- Rough idle or engine vibration
- Check Engine Light on
- Possible loss of power or poor acceleration
2. Most Common Causes
- Damaged or open circuit in the injector harness (VC harness) for cylinder 3
- Cylinder 3 injector coil internally open (infinite resistance)
- Corroded, loose, or retracted terminals at the injector or IDM connector
- Internal failure of the Injector Driver Module (IDM)
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect injector connector and wiring for damage or corrosion.
Step 3: Use a multimeter to measure resistance across injector terminals (should be 11-18 ohms).
Step 4: Check for voltage at injector connector with key on (should have battery voltage on one pin).
Step 5: Perform a continuity test from injector connector to ECM to rule out wiring issues.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as the misfire can damage the catalytic converter and cause poor fuel economy. Short trips to a repair shop are acceptable.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for diagnosis and repair, depending on whether the injector needs replacement or just wiring repair.
5. Commonly Affected Makes
This is a manufacturer-specific code. The exact manufacturer is not confirmed in our current database.