Technical Description of OBD-II Trouble Code
Glow Plug Sense Circuit
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to OBD-II equipped vehicles with glow plugs, specifically diesel engine vehicles. Various vehicle brands, including but not limited to Ford, Dodge, Mazda, VW, Ram, GMC, and Chevy, may be affected. While the code is generic, the 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.
The 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.
In essence, the glow plug functions similarly to an element on a stove-top. Diesel engines incorporate glow plugs because they do not use spark plugs to ignite the fuel/air mixture. Instead, they rely on compression to generate sufficient heat for ignition. Therefore, diesel engines require the assistance of glow plugs during cold starts.
The ECM triggers the P037D code and related codes when it detects a condition outside the specified range within the glow plug circuit. While most cases involve electrical issues, certain mechanical problems can also affect the glow plug circuit in specific makes and models. The P037D Glow Plug Sense Circuit code is set when the ECM detects one or more values outside the specified range.
Here is an example of a glow plug:
NOTE: If other dashboard lights are currently illuminated (e.g., Traction control, ABS, etc.), it may indicate another potentially significant problem. In such cases, it is advisable to take your vehicle to a reputable shop where they can use a proper scan tool to avoid causing any unnecessary harm.
This trouble code is closely related to P037E and P037F.
What is the severity of this DTC?
Generally, the severity of this code is moderate, but depending on the circumstances, it can be severe. For instance, if you live in moderate to extreme cold conditions, repeated cold starts with malfunctioning glow plugs can eventually cause damage to your internal engine components.
What are some of the symptoms of the code?
Symptoms of a P037D engine code may include:
What are some of the common causes of the code?
Possible causes for this code may 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 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 may lead you to the source of the problem. Excessive burning smells often indicate overheating. Carefully follow the smell and inspect for any burnt wire coatings or melting plastic around fuse boxes, fusible links, etc. Addressing these issues should be the priority.
NOTE: Thoroughly inspect all ground straps and look for corroded or loose ground connections.
Basic Step #2
Locate and trace the glow plug circuit harness. These harnesses are exposed to extreme heat, which can damage the wire looms designed to protect them. 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 a complete assembly from the vehicle. If this is feasible, you can use a multimeter to check for continuity in the individual wires of the circuit. This will help identify any physical problems within the harness. However, in certain vehicles, this step may not be possible. If that is the case, skip this step.
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 harnesses 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 this may vary depending on the make and model of your vehicle, so always consult the manufacturer’s service information FIRST.
