Obd2 Code P0138: Symptoms, Causes, Diagonose & Fix

Are you frustrated while thinking about how to fix the P0138 obd2 code? Well, guess what? You’re not alone. Millions of people are stuck with the same problem. This article is to help you fix it. It’s best to go through this article slowly and do each step patiently. It’s well worth it 😀

Often people ask whether they can drive with the P0138 code. You can drive a bit, but it’s not always a good idea to drive your car for too long with this code. This code error may result in catalytic converter/s damage. The best thing to do is go through all the steps below, which will help you fix the P0138 obd2 code.

Definition of P0138 obd2 code

The P0138 obd2 code usually appears on the Catalyst Control Module (bank 1). Banks are also known as cylinders. This code refers to a potentially life-threatening air system fuel pressure problem. P0138 code error means the system is facing issues getting enough fuel pressure from the fuel injectors or pump.

What does the P0138 code mean?

Do you know P0138 is an engine light code check? This indicates that the vehicle has an oxygen sensor problem. The car needs a diagnostic test to determine the actual problem, but it could be something as simple as a loose or dirty gas cap.

The P0138 obd2 code means that the Powertrain Control Module has detected a fuel pressure monitoring system problem. When this code first appears is usually related to a problem with the fuel pressure regulator.

The Car’s system gets commands from the powertrain control module. With these commands, it finds diagnostic trouble codes like fuel pressure problems. This information from the system is recorded in the Diagnostic Trouble Code (DTC), which is displayed on the driver’s instrument panel. 

What symptoms to look for P0139 code?

• Engine check light illumination.
• Loss of power.
• Your engine may not start or run properly.
• The engine may stall while driving and restart only after a few minutes or hours when it cools off.
• You may also notice trouble shifting gears.
• You might also smell rotten eggs, propane, or other unusual odors.
• The vehicle may start to run rough, especially during acceleration.

What causes the P0138 obd2 code?

Most causes of the p0138 obd2 code are related to a broken or damaged oxygen sensor. The oxygen sensor is a crucial part of the fuel system. It also detects the heat content of the exhaust gas. With it, the P0138 ob2 code common causes include:

• The fuel system is suddenly or gradually restricted.
• The water bypass valve may be partially clogged or damaged and not let the proper amount of water flow to the fuel system.
• The fuel pressure regulator might have failed or otherwise malfunctioned.
• The fuel system may be rusting and, therefore, slow to allow for the proper flow of fuel.

How to diagnose P0138 obd2 code?

Tools you need to Diagnose P0138 obd2 code

• A scan tools
• A Digital Volt Ohm Meter (DVOM)
• Live data mode scan tool.

Scan the vehicle to determine which cylinder bank has a problem.

Why? The code P0138 code may be stored in either bank 1 or 2. Check which cylinder bank has the highest voltage when the engine is running. The cylinder with the highest voltage will be the one with a problem.

How? Turn on the ignition switch. Turn the key to position 2. Get the digital volt ohmmeter connected with the connector attached to cylinder number 1 in bank 1 or 2. 

Once you know which cylinder has the problem, you can fix it. Cylinder 1 will be in bank 1, and cylinder 2 will be in bank 2.

Check for common causes of the p0138 obd2 code.

Why? If the oxygen sensor is not functioning, you will have a problem with the fuel system. You will have an inoperative fuel pressure regulator with a P0138 code. Check the fuel pressure regulator module to see if it needs any work.

How? Turn on the ignition switch. Now turn the key to position 2. Connect a digital volt ohmmeter to connector one on the fuel pressure regulator module.

Determine whether a rich or lean condition is present in the system.

Why? If the oxygen sensor detects too much fuel, the engine runs rich. The engine will run well but produce too much heat, and you will have a bad catalytic converter. If the oxygen sensor detects too little fuel, you will have a lean condition. The engine will run poorly and maybe idling funny.

How? Turn on the ignition switch. Now turn the key to position 2. Now on the fuel pressure regulator module connect the connector 1 with digital volt ohmmeter.

Check for any specific code.

Why? If you must check for specific codes, connect a scan tool, and enter the live data mode. Check for codes such as P0135, P0141, etc.

How? Turn on the ignition switch. Now turn the key to position 2. Connect a scan tool to the scan tool connector located on cylinder number 1 in bank 1 or 2.

Once you know which cylinder has the problem, you can fix it.

A common mistake you must avoid when diagnosing P0138 

A common mistake made by untrained automotive technicians is to replace the oxygen sensor first and then test it. This is not a good practice. Replacing the oxygen sensor could be expensive and a waste of time, especially if the problem doesn’t exist in the sensor. You will know what to replace after you have determined the cause of the problem.

How to fix the P0138 obd2 code?

What needs to be fixed depends on which cylinder bank has the problem. In cylinder bank 1, you will have a problem with the fuel pressure regulator or related components such as a fuel rail, fuel pressure regulator, or injectors.

The trouble with In-cylinder bank 2 can be in the fuel pressure regulator or components like the computer or the injectors. Here mostly the replacement is made for the fuel rail, fuel pressure, or regulator.

Replace the damaged parts! It would be better to get a better one. You can get a better fuel pressure regulator because the stock one will be damaged anyway due to a problem in the fuel system.

Tips for further avoiding P0138 obd2 error

• The fuel pressure regulator should not be used for any other purpose.
• When replacing the oxygen sensor, clean the old sensor first.
• Always replace the O-rings with a new sensor that you install.
• Use a DVOM to test your fuel pressure and make sure it is between 45 and 65 psi.
• Check the coolant system and make sure there is a proper amount of water in it.
• Check the coolant temperature if you run a coolant tester.
• Keep the spark plugs and other engine parts clean to improve performance.
• When replacing your O2 sensor, check for coil whine from the engine itself.

Cost of diagnosing the P0138 code

P0138 represents diagnostic problem codes for “O2- Sensor circuit high voltage (Bank 1). The causes of these codes are varied and require analysis of your situation. A Certified Mobile Car Service technician that can come in and repair any vehicle for a fee charged. Immediately after diagnosis a quote is given for the best possible solution.

If you have a P0138 code, the most common cause is a problem with the oxygen sensor. Now you can quickly diagnose the cause and get it repaired efficiently. Do follow the tips to avoid P0138 obd2 error in the future. Please comment if you face any problems or have any questions regarding this post.