Quick Answer
P0674 means: P0674 indicates a high input signal from the glow plug circuit for glow plug number 4.
Can I drive with P0674? Address this issue promptly to prevent starting difficulties and engine performance problems.
Common Questions
What does P0674 mean and how does it affect my car?
P0674 means there's an issue with the glow plug circuit for glow plug number 4, which can lead to starting difficulties and poor engine performance, especially in colder weather. Ignoring this code can cause longer cranking times and potential engine damage over time.
What are the most common causes of P0674 and how much does it cost to fix?
The most common causes of P0674 include a failed glow plug, faulty wiring, or poor connections. Repair costs can range from $100 to $300 for glow plug replacement, with potential additional costs if wiring or the ECM needs attention.
Can I drive my car with P0674 or should I stop immediately?
It's not advisable to drive with a P0674 code, especially in cold weather, as it may lead to starting issues and unreliable engine performance. It's best to have the issue diagnosed and repaired as soon as possible.
How can I diagnose P0674 myself using GeekOBD APP?
Start by connecting the GeekOBD APP to your vehicle's OBD2 port. Use the app to scan for trouble codes and note any additional codes present. Check the live data for the glow plug circuit to see if it’s operating within normal parameters. Follow the diagnostic steps to test the glow plug and wiring if necessary.
What vehicles are most commonly affected by P0674?
P0674 is commonly seen in diesel vehicles such as the 2005-2015 Ford F-250 and F-350 models. These vehicles may have specific recalls or technical service bulletins addressing glow plug issues, so it's important to check with your dealer.
How can I prevent P0674 from happening again?
Regular maintenance, including checking and cleaning electrical connections and replacing glow plugs based on manufacturer recommendations, can help prevent P0674. Keeping the battery in good condition and ensuring proper engine operation can also minimize the risk.
What is P0674?
The P0674 diagnostic trouble code (DTC) indicates an issue with the glow plug circuit of a diesel engine, specifically implicating glow plug number 4. Glow plugs are essential for starting diesel engines, especially in cold weather, as they preheat the combustion chamber to ensure smooth ignition. When this code appears, it signals that the engine control module (ECM) has detected a high input signal from the glow plug circuit, suggesting either a malfunctioning glow plug or a wiring issue. For instance, in vehicles like the 2005-2015 Ford F-250 or F-350, a failing glow plug can lead to hard starts, increased emissions, and rough idling. If the issue is left unaddressed, it can result in poor engine performance and even lead to increased wear on the engine. Drivers might notice symptoms such as extended cranking times, decreased fuel efficiency, or difficulty starting the vehicle in colder temperatures. Addressing this code promptly is essential to maintain engine health and performance.
System: P - Powertrain (Engine, Transmission, Emissions)
Symptoms
Common symptoms when P0674 is present:
- Check engine light illuminates and stays on, indicating an error in the glow plug system.
- Engine struggles to start, especially in cold weather, leading to frustrating mornings and potential battery drain.
- Rough idling and increased engine noise when running, suggesting that the engine isn't firing correctly.
- Decreased fuel economy, with owners reporting a drop of about 10-15% due to inefficient combustion.
- Excessive white smoke from the exhaust during startup, indicating unburned fuel and poor combustion.
Possible Causes
Most common causes of P0674 (ordered by frequency):
- The most common cause is a failed glow plug, which occurs in about 60% of cases. This typically results from wear and tear over time.
- A wiring issue or short circuit in the glow plug harness can account for 25% of P0674 occurrences, leading to improper voltage and signal.
- Poor connections or corrosion at the glow plug terminals can also trigger this code, emphasizing the need for regular inspections.
- Less common causes include a malfunctioning engine control module (ECM), which can incorrectly report the glow plug status.
- Rarely, a blown fuse related to the glow plug circuit can cause this code, but it is often accompanied by other codes as well.
P0674 Repair Costs
Cost Breakdown by Repair Type
Glow Plug Replacement
Replacing the faulty glow plug with a new unit.
- Total: $100 - $300
- Success rate: 85%
Wiring Repair
Repairing or replacing damaged wiring in the glow plug circuit.
- Total: $75 - $200
- Success rate: 90%
ECM Replacement
Replacing a malfunctioning engine control module, if necessary.
- Total: $500 - $1500
- Success rate: 95%
Money-Saving Tips for P0674
- Start with the most common and least expensive repairs first
- Use GeekOBD APP to confirm diagnosis before replacing expensive parts
- Consider preventive maintenance to avoid future occurrences
- Compare prices for OEM vs aftermarket parts based on your needs
- Address the issue promptly to prevent more expensive secondary damage
Diagnostic Steps
Professional P0674 Diagnosis Process
Follow these systematic steps to accurately diagnose P0674. Each step builds on the previous one to ensure accurate diagnosis.
Step 1: Step 1: Initial visual inspection - Check for damaged wiring, loose connections, or corrosion on the glow plug connectors (5-10 minutes)
Step 1: Initial visual inspection - Check for damaged wiring, loose connections, or corrosion on the glow plug connectors (5-10 minutes).
Step 2: Step 2: OBD2 scan with GeekOBD APP - Use the app to retrieve all codes and freeze frame data to understand the fault context (10-15 minutes)
Step 2: OBD2 scan with GeekOBD APP - Use the app to retrieve all codes and freeze frame data to understand the fault context (10-15 minutes).
Step 3: Step 3: Component testing - Use a multimeter to test the resistance of the glow plug and check for proper voltage at the harness (20-30 minutes)
Step 3: Component testing - Use a multimeter to test the resistance of the glow plug and check for proper voltage at the harness (20-30 minutes).
Step 4: Step 4: System function test - After repairs, verify proper operation of the glow plug circuit and clear the codes using the GeekOBD APP (10-15 minutes)
Step 4: System function test - After repairs, verify proper operation of the glow plug circuit and clear the codes using the GeekOBD APP (10-15 minutes).
Step 5: Step 5: Road test verification - Drive the vehicle under various conditions to confirm the successful repair and monitor for check engine light return (15-20 minutes)
Step 5: Road test verification - Drive the vehicle under various conditions to confirm the successful repair and monitor for check engine light return (15-20 minutes).
Important Notes
- Always verify the repair with GeekOBD APP after completing diagnostic steps
- Clear codes and test drive to ensure the problem is resolved
- Address underlying causes to prevent code recurrence
Real Repair Case Studies
Case Study 1: Glow Plug Replacement on 2010 Ford F-250
Vehicle: 2010 Ford F-250, 120,000 miles
Problem: Customer reported difficulty in starting the vehicle, especially in cold weather.
Diagnosis: Diagnostic scan revealed P0674. Visual inspection showed corrosion on the glow plug connector.
Solution: Replaced the faulty glow plug and cleaned the wiring connections.
Cost: $180 (Glow plug: $100, Labor: $80)
Result: Customer reported improved starting performance and no further issues.
Case Study 2: Wiring Repair on 2015 Ford F-350
Vehicle: 2015 Ford F-350, 85,000 miles
Problem: Check engine light was on, with rough idling and extended cranking times.
Diagnosis: P0674 was stored. Inspection revealed damaged wiring in the glow plug circuit.
Solution: Repaired wiring and replaced a damaged glow plug.
Cost: $250 (Repair: $150, Glow plug: $100)
Result: Vehicle started reliably, and customer noted enhanced performance.