P0003 trouble code definition
The P0003 code is associated with the electrical circuit which connects to your fuel pressure regulator.
It also may be related to other codes, such as: P0001, P0002, or P0004.
What the P0003 code means
P0003 is a generic OBD-II code indicating an issue with the engine control module (ECM) reading signals from your fuel pressure regulator on your fuel injection rail mounted to your engine.
The ECM regulates your fuel pressure from your fuel pump going to your engine through this circuit and receives input on your actual fuel pressure, from the fuel pressure sensor. When the computer detects that fuel pressure it is not commanding to the fuel pump, it will set a Check Engine Light and this code. The code will affect fuel economy and possibly damage the engine.
What causes the P0003 code?
The fuel volume regulator control circuit low code may have several causes:
- Possible corrosion in the sensor connector
- A short in the sensor wiring to the ECM
- A defective fuel pressure regulator
- The ECM is damaged
What are the symptoms of the P0003 code?
The P0003 code will produce a Check Engine Light on the instrument panel/dash and will likely affect:
- Your engine performance during driving
- Blown fuses
- Damage to the ECM
- Possible stalling while driving
- It may cause the exhaust to show black or white smoke
- Fuel economy
- Damage to the catalytic converter in your exhaust
How does a mechanic diagnose the P0003 code?
P0003 is properly diagnosed with an advanced scan tool capable of factory sensor readings (not just one from an auto parts store). A qualified technician can read the data from the advanced scan tool to determine when the problem occurred, or if it is still occurring. They may clear the code/light and test drive the vehicle while monitoring the scan tool data to see if the fault returns or is present.
Wiring may have to be inspected for damage, which requires cutting open the protective covering, inspecting the wiring harness, and replacing the covering.
Based upon the conditions of the testing, possibly clearing the code, and a road test while monitoring the data, further diagnosis may be required. Diagnosis may require multiple tools such as:
- An advanced scan tool to read the ECM data values
- A digital voltage meter with attachments
- A fuel pressure tester
Common mistakes when diagnosing the P0003 code
Just replacing the fuel pressure regulator never guarantees a successful repair in resolving your issue. It may be caused by several components in the fuel system and wiring as listed above or more.
A visual inspection and testing with special equipment listed above will verify your issue before unnecessarily replacing the fuel pressure regulator.
Electrical signals require evaluation by an advanced scan tool, a voltage meter, and a fuel pressure tester to ensure that the fuel pressure regulator requires replacement or if another problem exists. Additional inspection and testing may be required.
How serious is the P0003 code?
The P0003 fault code could cause your vehicle from running and it can:
- Lower your fuel economy
- Cause fuel instability which can cause permanent damage to your engine
- Damage your catalytic converters (which is an expensive repair)
- Damage your ECM (which requires special programming)
- Damage your wiring harness
- Prevent your vehicle from passing emissions
A qualified technician can diagnose the problem with proper tools and time to verify these potential issues and effects to your other systems.
What repairs can fix the P0003 code?
The most common procedure to repair the P0003 code are as follows:
Connect a professional scan tool. Verify the code exists.
Check for any other fault codes which may be related to the issue, then clear the fault codes to see which fault codes return.
Analyze scan tool data from the ECM.
Road test the vehicle while analyzing the scan tool data from the ECM with other tools attached.
Verify if the P0003 code returns.
Inspect all of the items listed above. (wiring, voltages, etc)
Further diagnose the problem with the special tools listed above if the problem appears to repeat. The signals and wiring from the sensor require analyzation to determine where the problem exists. If the signals are fine, then further testing of the the wiring, computer, or fuel system is required.
Additional comments for consideration regarding the P0003 code
Any sensor issue may occur all the time or intermittently. Some fault codes will require additional time to diagnose. With this code, the solution may be simple to replace or require extensive time to diagnose and repair. Depending on your vehicle, it may take several hours to determine the root cause and repair the faulty component.
The P0003 code involves many systems and requires extensive diagnosis. After using a scan tool and monitoring the voltage readings, a qualified technician could determine if the fuel pressure regulator, wiring, or ECM is at fault. With the scan tool connected I typically evaluate the data while checking the voltage meter to ensure all the values are adequate and match specifications and do not have shorts in the circuit. If there is not a specified voltage, then a further diagnosis is required.
The sensor may be the cause, wiring issues might be burning/rubbing on another engine component, rodents may have chewed through wiring anywhere in the vehicle, connectors may have shorts or damage, or you may have a bad ECM caused by the short.
An advanced scan tool with specialty tools inspection is required. Then we will determine where the fault lies. We may clear the fault code/light first, then verify if the check engine light returns, and diagnose further. It may have been an intermittent occurrence from weather or some other factor, or a permanent concern.
Vehicles with higher mileage (over 80,000 miles) may just need a fuel pressure regulator replacement. However, replacing parts based upon a code is not recommended and has caused problems or not resolved the issue.
Need help with a P0003 code?
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This article originally appeared on YourMechanic.com as P0003 OBD-II Trouble Code: Fuel Volume Regulator Control Circuit Low and was authored by Paul Lancette.