P1274: Cylinder #4 Injector Circuit High to Low Side Open
The P1274 code indicates an open circuit between the high and low sides of the fuel injector driver for cylinder #4. This typically means the injector coil has failed (open circuit) or there is a wiring issue between the ECM and the injector. The ECM monitors the current flow through the injector; when it detects an open circuit, it sets this code. This can cause a misfire, rough idle, and reduced engine performance.
1. Symptoms You Will Notice
- Check Engine Light on
- Engine misfire on cylinder #4
- Rough idle or hesitation
- Decreased fuel economy
- Possible hard starting
2. Most Common Causes
- ECM replaced without programming the immobilizer code
- New or replacement key not programmed correctly
- Immobilizer module (NATS) failure
- Loss of ECM memory data due to dead battery or battery disconnection
- Transponder antenna (ring around ignition cylinder) damaged
- Data bus communication failure between ECM and immobilizer module
- BCM (Body Control Module) replaced or has corrupted data
3. Step-by-Step Diagnosis
Step 1: Scan for codes and verify P1274 is present. Check for other related codes.
Step 2: Visually inspect the injector connector and wiring for damage, corrosion, or loose connections.
Step 3: Measure resistance across injector #4 terminals (should be 11-17 ohms). If open (OL), replace injector.
Step 4: If injector resistance is good, check for voltage at injector connector with key on (should see battery voltage on one pin). If no voltage, check wiring and ECM fuse.
Step 5: Perform a continuity test from the injector connector to the ECM. Repair any open or short circuits found.
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 and repaired promptly.
How much does it cost to fix?▼
If the injector needs replacement, parts cost $50-$150 and labor $100-$250, totaling $150-$400. Wiring repairs may be less.
5. Commonly Affected Makes
This is a manufacturer-specific code. The exact manufacturer is not confirmed in our current database.