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P0169 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

One of the most crucial components inside your vehicle is the fuel you use. If it isn’t burning smoothly, you could wind up wasting far more than you should. In some cases, bad gasoline can even cause engine damage. 

If your check engine light came on and you discovered OBD2 code P0169, it means that there is a problem with your fuel. Here is a breakdown of how to diagnose and correct this issue. 


Incorrect Fuel Composition


Gasoline is a mixture of different elements, including up to 150 hydrocarbons like butane. Some fuels include ethanol to help the mix burn cleaner and produce fewer emissions. 

Code P0169 means that the powertrain control module (PCM) has detected excessive contaminants or ethanol in your gas. If ethanol is the source, the code indicates that the blend is more than 85 percent. 


Contaminants get into your fuel system all the time. If you haven’t cleaned and flushed the system in a while, it may be time to do so. One particular issue is water getting into the tank. Since ethanol absorbs water, it can get heavier and sink to the bottom, called phase separation. When this happens, you’ll get more of an ethanol/water mixture over time, leading to this code. 

Typically, water gets into your fuel tank through condensation. It can also be coming in through the gas pump if the station you buy from doesn’t prevent phase separation. 

Other causes of this code include a faulty composition sensor, damaged or shorted wiring connectors to the PCM, or an error with the powertrain control module itself. 


Unfortunately, this code can cause significant damage to your fuel system and engine, but it doesn’t usually show any noticeable signs beforehand. In many cases, the only warning you have that your gasoline is contaminated is the check engine light itself. 

Because P0169 can strike without other warnings, it illustrates the importance of using an OBD2 scanner to identify engine issues as soon as possible. If you let it go on too long, you could wind up with a substantial repair bill. 


The simplest way to determine whether your fuel is actually contaminated is to rule out a PCM or wiring issue. 

To do this yourself, you will need a device that has an oscilloscope and a digital volt/ohmmeter (DVOM). You will also need a diagnostic scanner to check the PCM to see if it’s working properly. 

First, you’ll have to locate your fuel composition sensor. It is next to the fuel temperature sensor in a single housing unit. Refer to your owner’s manual to find it. Be sure to inspect the wires coming out of the housing to see if they are damaged. If not, you can continue diagnostics. 

Next, you’ll need to check the voltage coming out of the sensor with the DVOM. You will have to find source information on your vehicle to ensure that the readout is correct. Otherwise, you will have no frame of reference. 

If the voltage coming out of the sensor is good, the next step is to check the PCM voltage. If that is correct as well, the problem could be the fuel temperature. 

To check the temperature, you will need an infrared thermometer and an oscilloscope. Plug the oscilloscope into the temperature sensor, then measure the actual heat with the thermometer. If they don’t match, the sensor may be faulty. 

If all of these components seem to be working correctly, that means the problem is contaminated fuel. You can avoid these steps by taking your car to a mechanic who has all of these tools. It will cost more, but it is far more convenient. 

Common mistakes

If you’re unfamiliar with using a DVOM or oscilloscope, you won’t be able to tell the readings. You also have to make sure that you have a reference manual to compare against so you can be sure that the sensors are working properly. 

Another common mistake is assuming that an undamaged sensor or wire is working. Just because they don’t look broken doesn’t mean that they are in good condition. 

How serious is this?

A P0422 trouble code can vary in the level of its severity. The code is caused by a faulty catalytic converter, the vehicle may stall frequently or not start at all. In this circumstance, the car may be partially or completely not drivable.

If the catalytic converter is not the source of the problem, you may notice little to no problems with the drivability of the vehicle. In either case, the code should be investigated by a mechanic so they can identify and fix the problem.

What repairs can fix the code?

repair manuals

If the sensors or PCM are the issue, you will need to replace them. In some cases, even if the temperature sensor was working, you might have to get a new one anyway, since high heat can damage the internal components. If that happens, the sensor could cause faulty readings after you reset the check engine light

If the fuel is contaminated, you will have to perform an engine flush to get all of the old fuel out. Once that is finished, reset the code and add new gasoline to the system. Run the car for a few minutes to ensure that the light doesn’t come back on. 

Related codes

  • P0180 – Malfunction in the fuel temperature circuit.
  • P0182 – Low input in the fuel temperature circuit.
  • P0168 – Fuel temperature is too high.


Most drivers don’t do anything to clean their fuel systems, leading to contaminations and problems like code P0169. Ideally, you will add cleaning agents to your gas annually to keep it running smoothly. Since P0169 is related to flex fuels (gas/ethanol mixes), their composition is even more critical. Above all – don’t ignore your check engine light

P0169 Code – What Does It Mean & How To Fix It