4 Reasons Why Check Engine Light On After Car Washing

If your check engine light appears on your dashboard after going through a car wash, it may or may not be a problem. The check engine light could have been tripped by some moisture. Water may have gotten into the engine and is damaging integral pipes and wires that will cost hundreds to replace. 

Reasons Why Check Engine Light On After Car Washing

Water damage is a common enemy. Automobile manufacturers have been developing new ways to protect vehicles from moisture since the invention of the automobile.

But sometimes, the machines we use to keep our vehicles clean are the ones that damage them.

Here are common issues that appear after visiting the car wash.

Sensors In And Around The Engine Were Damaged

There are a few ways water can get into the main engine compartment and around the battery. If your vehicle’s accidentally submerged in water, the water can sleep in from all sides and underneath the vehicle and damage the battery. 

Also, the hood may not protect the vehicle from water damage, especially an angled spray, like at a car wash. When water seeps into the engine compartment, it may mix with other dirt, grime, and debris that made its way into the apartment as well. 

These sludgy materials can mix together and cause damage to the engine or to the battery. Water and grime can damage the sensors. A vehicle’s internal monitoring system requires the sensors to function adequately in order to detect issues. 

But a broken sensor is an issue as it cannot accurately provide data to the vehicle’s computer system. When there is a broken sensor around the engine, the check engine light will go off.

The manufacturer of the vehicle did not seal the vehicle correctly

Vehicle issues caused by the manufacturer are not a stranger to the automobile industry. Poor navigation systems, bad software, and issues with the braking system are all scandals that have happened in the last couple of years by Ford, Lexus, and Mercedes-Benz. 

So it isn’t a stretch to consider that the manufacturer of your vehicle did not secure and protect your vehicle from water damage like they should. Or maybe they did, but they accidentally sold a dud that was not caught by quality control before it was shipped out.

Also, older cars will have more gaps and openings than newer cars. Water can slip into the gaps easily and affect the mechanisms.

Water is in the air intake system

If you have a vehicle whose air intake system is around the lower part of the vehicle, then you may have to deal with more water issues than other vehicles. 

Vehicles with mass air flow sensors located inside fuel injectors can prevent excessive amounts of air from entering the cylinders when the engine is on. The air intake or mass sensors regulate how much fuel goes into each cylinder.

If only a small amount of water is in the air intake system, then the heat from the engine should evaporate. However, if there is a significant amount of water in the air intake system, hire a mechanic to clean out the air and any mold or grime that accumulated in the piping.

Your catalytic converter is failing

This is one of the worst issues that can happen after visiting the car wash. The catalytic converter is a device that reduces the number of emissions and smogs your vehicle puts out when the engine is on. 

It is a fundamental part of your vehicle and if your catalytic converter does not work correctly, you cannot pass the smog check. If you cannot pass the smog check, your vehicle will be illegal to drive even if you have a license and insurance. 

When there is an issue with the catalytic converter, your check engine light, along with a few other warning lights, will appear. 

You’ll know if the catalytic converter is the real problem if your fuel efficiency drops significantly, you have regular engine misfires, and you hear a rattling noise from the engine. Replacing a catalytic converter is expensive, as they usually range from $800 to 1,200. This price only accounts for the cost of the device and not for labor.

What should you do when your check engine light appears

When the check engine light appears, don’t ignore it and keep on driving. Many people ignore their check engine lights and the problem grows and grows. Schedule a regular maintenance check with your mechanic and have them investigate the check engine light. They will use their diagnostic tools to find the reason the engine light is on. Tell them you were at the car wash recently so they can be on the lookout for moisture damage as they service your vehicle.

The check engine light-up keeps appearing even though I got it checked. 

If the check engine light keeps lighting up day after day, then they actually could be an issue with the check engine light itself. Sometimes wiring can become damaged through moisture or jerky movements. So have your mechanic check the dashboard lighting system and see if the check engine light fuse blew out or the wire ring is bad.


After visiting the car wash, your vehicle may experience some issues. It is common for water to find its way into the air intake system. The best and easiest way to find any issues that are happening in the automobile that is causing the check engine light to turn on is to use the diagnostic codes. Your mechanic can look at the diagnostic codes and find out which areas of the vehicle are malfunctioning.

  • Eric Williams

    I'm the founder of Daily Car Tips. I wrote articles in the automotive industry for more than 10 years, published in USA and Europe. I love sharing my knowledge and insights with fellow enthusiasts. Join me on this journey as we explore the exciting world of cars together!

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