What Does It Mean?
The diagnostic trouble code (DTC) P037F is a generic powertrain code that applies to OBD-II equipped vehicles with glow plugs (diesel engine vehicles).
Affected brands include, among others: Ford, Dodge, Mazda, VW, Ram, GMC, and Chevy. Although generic, repair steps may vary depending on the vehicle’s make, model, and engine. This code appears to be more common on Ford vehicles.
Glow plugs and their circuits are responsible for generating heat in the combustion chamber before cold starts. They function similarly to a stove element and are essential because diesel engines use compression rather than spark plugs to ignite the fuel/air mixture.
The ECM (engine control module) sets the P037F code when it detects an abnormal electrical value in the glow plug circuit. Most of the time, it is an electrical issue, although some mechanical problems can also influence this circuit.
This code is closely related to codes P037D and P037E.
Severity of Code P037F
The severity of this code is moderate, but it can be severe in certain situations. For example, if you live in an area with very cold temperatures, repeated cold starts with faulty glow plugs can cause internal engine damage.
Symptoms of Code P037F
Here are the signs that may indicate the presence of this code:
- Difficulty starting in cold weather
- Abnormal engine noises during startup
- Poor engine performance
- Engine misfires
- Increased fuel consumption
Possible Causes of Code P037F
Several causes can be at the origin of this problem:
- Broken or damaged wiring harness
- Blown or defective fuse link
- Faulty glow plug
- Problem with the ECM
- Damaged connectors or pins (corrosion, overheating, etc.)
Troubleshooting Steps
1. Check Technical Service Bulletins (TSBs)
Before any diagnosis, consult your vehicle’s technical service bulletins. A known fix could save you unnecessary time and expense.
2. Required Tools
To work on electrical circuits, it is recommended to have the following tools:
- OBD code reader
- Multimeter
- Socket and ratchet set
- Screwdriver set
- Shop rags/towels
- Battery terminal cleaner
- Vehicle service manual
3. Safety Tips
- Allow the engine to cool before any intervention
- Block the wheels to prevent any unintended movement
- Wear personal protective equipment (PPE)
4. Diagnosis and Repair
Step 1: Visual Inspection
- Open the hood and check for any burning smell.
- Look for melted wires or damaged fuse boxes.
- Inspect ground connections (corrosion, connection faults).
Step 2: Wiring Harness Inspection
- Follow the glow plug harness and look for damage.
- Check areas where the harness might rub against the engine or other components.
Step 3: Wire Continuity Check
- If possible, disconnect the glow plug harness and test continuity with a multimeter.
- If this is not possible on your vehicle model, proceed to the next step.
Step 4: Electrical Circuit Testing
- Consult manufacturer specifications for expected voltage values.
- Use a multimeter to test the involved circuits.
Step 5: Glow Plug Testing
- Disconnect the glow plug harness.
- With a multimeter in voltage mode, place one probe on the battery’s positive terminal and the other on the tip of each glow plug.
- The voltage should be equal to the battery voltage. A different value indicates a problem with the glow plug.
- Always consult manufacturer information before performing this test.
Conclusion
The P037F code indicates a problem with the glow plug circuit and can cause starting difficulties, performance losses, and excessive fuel consumption. A thorough diagnosis following the steps above can help you resolve the issue and avoid damaging your engine.