P1264: High to Low Side Short in Cylinder #4 Injector Circuit
The P1264 code indicates a short circuit between the high and low sides of the fuel injector circuit for cylinder #4. This typically occurs when the injector's internal winding fails or the wiring harness is damaged, causing a direct electrical connection between the power and ground circuits. This can lead to injector malfunction, misfires, and potential damage to the engine control module (ECM) if not addressed.
01. Most Common Causes
- Faulty fuel injector on cylinder #4 (internal short)
- Damaged wiring or connector for injector #4
- Corrosion or moisture in the injector connector
- ECM internal failure (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Engine misfire on cylinder #4
- Rough idle or hesitation during acceleration
- Decreased fuel economy
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to confirm P1264 and check for other codes.
Step 2: Visually inspect the injector #4 wiring and connector for damage, corrosion, or loose pins.
Step 3: Measure resistance across injector #4 terminals (should be 11-16 ohms for most vehicles). A short will show near 0 ohms.
Step 4: Perform a continuity test between injector #4 high and low side circuits at the ECM connector to isolate the short.
Step 5: If injector is faulty, replace it. If wiring is damaged, repair or replace the harness.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. Driving with a shorted injector can cause misfires, reduce engine performance, and potentially damage the catalytic converter or ECM.
How much does it cost to fix?▼
The cost typically ranges from $150 to $400, including parts (injector $50-$150) and labor (1-2 hours at $100-$150/hour).