OBD-II Trouble Code Technical Description
The glow plug sense circuit is registering a high voltage.
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to OBD-II equipped vehicles with glow plugs, typically found in diesel engine vehicles. This includes brands such as Ford, Dodge, Mazda, VW, Ram, GMC, Chevy, and others. While the code is generic, the specific repair steps may vary depending on the make, model, and engine. It is worth noting that this code appears to be more common in Ford vehicles.
Glow plugs, along with their associated harnesses and circuits, are part of a system responsible for generating heat in the combustion chamber before cold startups. They function similarly to the heating element on a stove-top. Diesel engines rely on compression rather than spark plugs to ignite the fuel/air mixture, so glow plugs are essential for cold starts.
The ECM (Engine Control Module) triggers the P037F code and related codes when it detects a condition outside the specified range within the glow plug circuit. While electrical issues are the most common cause, mechanical problems can also affect the glow plug circuit in certain makes and models. The P037F code indicates that the ECM has detected one or more high electrical values within the circuit.
Here is an example of a glow plug:
NOTE: If other dashboard lights are currently illuminated, such as traction control or ABS, it may indicate a larger underlying problem. In such cases, it is recommended to take your vehicle to a reputable shop where they can use a proper scan tool to diagnose the issue and prevent any unnecessary damage.
This trouble code is closely related to P037D and P037E.
What is the severity of this DTC?
Generally, the severity of this code is considered moderate. However, depending on the circumstances, it can be severe. For instance, if you live in moderate to extreme cold conditions and experience repetitive cold starts with malfunctioning glow plugs, it can eventually lead to damage to internal engine components.
What are some of the symptoms of the code?
Some symptoms associated with the P037F engine code may include:
What are some of the common causes of the code?
Possible causes for this code include:
What are some troubleshooting steps?
It is recommended to check for any technical service bulletins (TSBs) related to your vehicle. Accessing a known fix through TSBs can save time and money during the diagnosis process.
Tools
When working with electrical systems, it is advisable to have the following basic tools:
Safety Tips
Basic Step #1
In this situation, the first step would be to open the hood and check for any unusual burning smells. If present, this could indicate a problem. Excessive burning smells often indicate overheating. Carefully follow the smell and look for any burnt wire coatings or melting plastic around fuse boxes, fusible links, etc. Addressing these issues should be the priority.
NOTE: Inspect all ground straps visually and look for corroded or loose ground connections.
Basic Step #2
Locate and inspect the glow plug circuit harness. These harnesses are exposed to extreme heat, which can damage the wire looms designed to protect the wires. Pay special attention to any spots where the harness may rub against the engine or other components. Repair any damaged wires or looms.
Basic Tip #3
If possible, disconnect the glow plug harness from the plugs. In some cases, you may be able to disconnect it from the other side of the harness as well and remove it as an assembly from the vehicle. If this is possible, you can use a multimeter to test the continuity of the individual wires in the circuit. This will help identify any physical problems within the harness. However, in some vehicles, this step may not be feasible, so you can skip it.
NOTE: Always disconnect the battery before performing any electrical repairs.
Basic Step #4
Test the circuits according to the manufacturer’s specifications for desired electrical values. Using a multimeter, you can perform various tests to verify the integrity of the involved circuits.
Basic Step #5
Test the glow plugs. Unplug the harness from the plugs. Using a multimeter set to Voltage, connect one end to the positive battery terminal and touch the tip of each plug with the other end. The values should match the battery voltage. If they do not, it indicates a problem with the plug itself. Keep in mind that the specific values may vary depending on the make and model of your vehicle, so always refer to the manufacturer’s service information as the primary source.
