How To Troubleshoot & Fix P1521 Jeep DTC Code?

Diagnostic Trouble Codes of the jeep are of great help as they alert you where and what the issue is. P1521 is one such trouble code, which is considered moderately severe.

It indicates incorrect engine oil viscosity, and thus requires immediate attention. No need to be worried about it. you’re going to have every nook and corner of the matter. Stay tuned!

What Does P1521 Jeep Code Mean?

In simple language, For the jeeps, the trouble code P1521 indicates the incorrect type of engine oil. In another language, the code is stored when the viscosity of the engine oil is not ok.,

The Powertrain Control Module, also known as the PCM, receives data from the oil temperature sensor, and oil pressure, which allows the PCM to calculate the engine oil’s viscosity. 

Your jeep receives the Diagnostic Trouble Code or DTC P1521 when the PCM determines the incorrect oil viscosity. 

When there is incorrect viscosity of the oil of the jeep, it hampers the MDS or the Multi-Displacement System functions by delaying the cylinder activation. 

Here is the breakdown of the P1521 trouble code. 

  • P= Powertrain [It covers the components that include transmission, engine & other associated accessories of the drivetrain] 
  • 1= Manufacture specific number derived from the SAE standard
  • 5= Incorrect engine oil type
  • 21= Specific Fault index [Oil velocity is not ok]

P1521 Code: What Causes Incorrect Engine Oil Type On Jeep?

P1521 is the code for the incorrect oil type used in the jeep. If you have recently changed the oil or, by chance, if the correct type of oil is not used, the PCM sets the code in your jeep. 

Apart from this, there are several causes behind the fault code on the jeep. Here are they- 

  • Incorrect oil type 
  • Contamination of oil 
  • Defective engine oil pressure sensor
  • Faulty Powertrain Control Module [PCM]

Read Also: How to troubleshoot & Fix C121C Jeep DTC Code?

How To Troubleshoot & Fix P1521 Jeep Code?

Whenever there is a faulty engine oil condition like the wrong oil type or contaminated engine oil, the P1521 trouble code triggers in your jeep. 

As for fixing the trouble code issue in your jeep, you should always perform pre-diagnostic troubleshooting before proceeding to inspect the possible damages. Let us move ahead to troubleshoot the issue step by step.

#1- Change The Wrong Type Of Engine Oil

The first that you need to do to resolve the trouble code in your jeep is to check the engine oil. 

If you have changed the oil of your jeep recently, check whether you are using the correct type of fluid for your vehicle. 

If the wrong type of oil is detected, change the engine oil.  Always choose high-quality fuel for your jeep. 

Check for the gas tank to see whether it is closed securely. Examine the oil level. Add more oil to the tank in case the oil level is lower than the maximum. 

Now connect the scanning tool and read the DTC using the device. If the DTC is no longer active, you have completed the troubleshooting. If that is not the case & the DTC is still active, move ahead to the next step.

Read Also: How to Troubleshoot & Fix P0128 Jeep Wrangler DTC Code?

#2- Flush The Contaminated Engine Oil

The next important thing is to flush contaminated oil. When the engine oil gets contaminated, it increases the viscosity of the oil which triggers the trouble code P1521 in your jeep. 

So, if you are using the correct type of oil but still have the trouble code, check whether the oil in the engine is contaminated. 

If it is, you may need to flush the dirty engine oil. To do so you can use one of these 3 ways-

Method 1:

  • Remove a small amount of oil from the engine of your jeep. 
  • Add non-solvent flush additive chemicals into the system. 
  • Now take your jeep for a test drive so that the vehicle can utilize the chemical throughout the engine. The deposits will become loosened and will be trapped in the filter. 
  • Lastly, get the oil changed with a new filter. 

Method 2: 

  • Here also remove a small amount of oil from the engine and add non-solvent flush additive chemicals into the system. 
  • Now idle your jeep for 5 to 10 minutes without driving. This will allow the sludge to suspend into the filter.
  • Change the engine oil with a new filter. 

Method 3:

  • Drain out the oil from the engine & add clean oil that contains non-solvent chemicals. 
  • Now drive your jeep or idle it for a few minutes so that the clean oil can reach every part of the engine. 
  • To ensure the better condition of the engine, you can change the oil and the filter. 

#3- Replace The Faulty Oil Pressure Sensor 

In your jeep, if the oil temperature or the oil pressure is set along the P1521 code, you have to repair them with the diagnosis of the P1521 code. 

Inspect whether the oil pressure sensor of your jeep is damaged, triggering the DTC code. 

If you find it faulty, replace it with a new one. Replacing the oil pressure sensor may cost you $331. Replacing price may vary according to the models of your jeep plus your living place.

Read Also: How To Troubleshoot & Fix p1494 Jeep DTC Code?

#4- Reprogram the Powertrain Control Module

The DTC or the Diagnostic Trouble Code can be set on the ambient temperature conditions of the jeep even when you have used the correct type of fluid with the correct fluid viscosity. 

If you have not changed the oil recently or are using the correct viscosity of the fluid, but the code keeps coming back, then it can be the PCM issue. 

The Powertrain Control Module needs to be selectively erased and reprogrammed with the dealer’s help with a factory scanning tool and software. Reprogramming the PCM module can take an average of ½ hour of labor time.

Read Also: P0455 Jeep Wrangler Code: EVAP System Large Leak Detected

Frequently Asked Questions [FAQs]

By now, we expect that you have got a clear idea of your queries related to the P1521 trouble code that you are experiencing. Still, here in this subsection, we have covered some of the most searched queries that can help you gain more ideas about the matter. 

Can you drive a Jeep with P1521 Code?

It is not a good idea to drive with the P1521 code. Due to the wrong type of fluid, there can be a lath of lubrication in the engine, overheating, and a possibility of transmission failure. So better to get the issue resolved soon. 

How Much Does It Cost to Fix Jeep P1521 Code?

The diagnostic cost of the Jeep P1521 code is per hour of labor. The diagnosing and repairing time varies from place to place, the vehicle’s model, and the engine’s type. It will cost $75 to $150 per hour of labor. 

Why am I getting the P1521 code even after changing the oil?

If you are still getting the P1521 code in your jeep even after changing the oil, then that means the oil pressure sensor of your vehicle has failed. Now you need to replace it at the cost of $331. 

Final Thoughts 

A diagnostic trouble code is set on your vehicle whenever the computer detects any faults that your vehicle encounters that can be severe or not. 

As the P1521 jeep code is set for the wrong type of fluid in the vehicle, you should not take the matter lightly. 

The wrong type of fluid can cause severe damage to the engine. So, take the initial steps for fixing the trouble code as soon as possible.

Read Also: How To Troubleshoot & Fix P0138 Jeep Code? A Detailed Guide

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