Lexus Check Engine Light Troubleshooting Guide

Vehicle:   Lexus
Difficulty: ⚫⚫⚫⚪⚪
DIY Cost: $15-$250
Est. Time: 15 min - 1 hr

In this guide, you will learn about the Lexus check engine light, symptoms, common problems, and how to read the codes via the OBD-II port. 

In case there are engine or emission-related problems, a yellow check engine or "service engine soon" light will illuminate on your dashboard.

In some cases, the message could be due to the cruise control, TRAC Off, or a VSC light, even though there may be no issues with these systems. 

What Does Lexus Check Engine Light Mean?

lexus check engine light

Lexus check engine light means that the On-Board Diagnostic (OBD) system has detected a problem.

This could be as simple as a loose gas cap or a more severe problem like a bad VVT solenoid, bad spark plugs, catalytic converter, or even transmission issues.

A fault code will be stored in the OBD computer and can easily be read with an OBD2 scanner. The fault code provides clues as to why your Lexus check engine light is on.

Symptoms

Common symptoms that you will notice when Lexus check engine light stays on include:

  • rough idling
  • poor acceleration
  • engine not starting
  • engine shakes at idle
  • rough shifting
  • TRAC OFF, VSC light on

You also might notice that the car is misfiring or overheating. However, sometimes there are no symptoms at all.

If your Lexus seems to be running fine, but the check engine light still comes on, don't brush it off. Please make sure you get it checked as soon as possible.

What to do when Lexus's check engine light comes on?

When your Lexus check engine light comes on, we recommend checking a few basic items before continuing your journey. Do not continue to drive if the check engine light is flashing.

  1. Check the gas cap. If the gas cap is loose, tighten it until you hear it click. Once you tighten the gas cap, it can take up to one week for the engine light to reset on its own. Or use an OBD2 scanner to reset it yourself.TIGHTEN LEXUS GAS CAP
  2. Check engine oil level. Turn off the engine. Wait at least 15 min. Open the hood. Pull out the dipstick and wipe it clean. Reinsert it and remove it to read the engine oil level. The level should be between the Min and Max marks.LEXUS CHECK ENGINE LIGHT ON, CHECK ENGINE OIL LEVEL
  3. Allow the engine to cool down and check the engine coolant level.check engine coolant level
  4. Monitor warning lights and engine temperature. Do not continue to drive if the check engine light is flashing, the engine is overheating, or the oil light turns on. leuxs warning light on
  5. Read Lexus engine fault codes using an OBD2 scanner as soon as possible. See the instructions below.read diagnose lexus check engine light

What Causes Lexus Check Engine Light to Come On

lexus engine

The most common problems that trigger the check engine light on a Lexus are worn spark plugs, bad oxygen sensors, and loose gas cap. 

Common causes for Lexus check engine light to be triggered are:

Spark Plugs

A spark plug that no longer fires is one of the most common problems that trigger the check engine light on Lexus vehicles.

Many owners don't realize that spark plugs are wear and tear items and need to be replaced according to the owner's manual's recommendation. Typically 120,000 miles.

On older Lexus vehicles equipped with copper spark plugs, you had to change them every 30,000 miles. Newer models are equipped with Platinum or Iridium spark plugs that can last over 100,000 miles.

Ignition Coils

Ignition coils are in charge of generating electricity for the spark plugs. Older Lexuses only have one ignition pack, while newer cars have one ignition coil per cylinder.

If something is wrong with the ignition coils, it will most certainly trigger the check engine light and codes such as P0300, P0301, P0302, P0303, P0304.

Remember, if you have a diesel Lexus such as LX450 V8 diesel, it doesn't have ignition coils, so this won't be the problem.

VVT System Malfunction

Most Lexus engines have variable intake manifolds, which are a bit more complicated. This added complexity makes them more prone to intake leaks, resulting in a lean running engine.

You will usually experience symptoms such as rough idle, lack of power, or hesitation on accelerations. Such behavior can also be caused by a dirty MAF sensor, giving false air quantity readings.

If in doubt, clean the MAF sensor, but remember to use only the MAF cleaner fluid for this. Codes: P0171 and P0174

The Variable Valve Timing (VVT) sensor varies the oil pressure, which changes the valve lift's timing. The cams will either advance or retarded the timing depending on engine speed and load.

Different factors could cause the VVT system to malfunction, like a defective Oil Control Valve (OCV) solenoid, dirty or low engine oil, a problem with the valve timing, or a problem with the VVT controller assembly.

If you have VVT problems, you may get fault codes such as P1354, P1349, and P1351. Also, the engine will idle rough and feel underpowered.

Possible solutions will be to clean the VVT valves, replace the cam sensors, replace the OCV solenoid. 

Loose Gas Cap

Another reason Lexus check engine light comes on is a loose gas cap.

The gas cap is a key part of your car,s fuel delivery system, so if it,s not tightened properly, it could lead to gasoline fuels leaving the tank.
If the light turns on immediately after filling up your tank, this is a good place to check first.

Sometimes it just needs to be tightened a little bit more.

Catalytic Converter

One that is particularly common on Lexus vehicles is the converter under-heating. A lot of people who have Lexus vehicles have reported this issue.

They found that the converter seemed to be working fine, but the sensor didn't think it was. So that's something specific to watch out for.

Catalytic converters can start to clog up as well if the car has over 150,000 miles.

Oxygen Sensor

If you have a high-mileage Lexus, it is very likely to have a check engine light caused by an emission-control related issue.

Although stored codes will usually point to a catalytic converter low efficiency, it is easily possible that you have a faulty downstream o2 sensor. Make sure to rule this out before changing a much more expensive catalytic converter. Code: P0420 (Catalyst Efficiency Below Threshold)

Oxygen sensors (O2) may trigger a check engine light to come on. A common fault code triggered by a bad Lexus oxygen sensor is P1150, P1133, P1153 related to AF Sensor, which means the circuit for the heater element of the O2 sensor is defective.

To fix this problem, you will need to replace the oxygen sensor. Changing a Lexus O2 sensor is simple as long as it is one of the oxygen sensors that are easy to access.

Idle air control valve

Older Lexus cars with a cable operated throttle can suffer from rough idle and hesitation when accelerating from idle.

The problem usually lies within the idle air control valve, blocked by dirt, oil, or carbon build-up. Use This carb-cleaner to remove the build-up.

Code P0505

EVAP System

If you are getting codes related to the EVAP system, first check if the hose that connects to the solenoid mounted on the engine intake isn't broken.

Other usual causes are bad fuel cap, leaking purge valve, damaged EVAP canister, or cracked lines.

Codes P0441 and P0445.

Camshaft Position Sensor

It is not unusual for a camshaft position sensor to fail. This usually manifests itself with hard starting, stalling, and constant or intermittent rough running.

Luckily, on most models, the camshaft position sensor is quite easy to replace.

Code: P0340.

Oil Sludge

Oil sludging is a serious problem that affects most cars made in the 2000s. This is caused by a blocked crankcase ventilation valve, also known as a PCV valve.

This can cause various problems ranging from high oil consumption, rough idle or a check engine light, and even a complete engine failure at highway speeds.

Visible symptoms are blue smoke on startup or acceleration and yellow gunk on the oil filler cap.

You could also get emission control related codes, such as P0420.

How to Reset Lexus Check Engine Light

This section shows you how to read and clear Lexus check engine fault codes (also known as Diagnostic Trouble Codes or DTC) using an OBD2 scanner. We do not recommend clearing codes without fixing existing problems. 

  1. Locate the OBD2 port under the dashboard—plugin your OBD2 scanner.lexus obd2 port
  2. Turn on the ignition but do not start the engine.lexus engine on
  3. Allow your OBD2 scanner to turn on and communicate with your Lexus.reset lexust check engine light
  4. Select Read codes from the main menu.

Fault codes will display on the OBD2 scanner, such as P0300, for example. Write down all the codes and do further research to understand what they mean and learn about possible causes.

After the problem has been resolved, you'll need to reset Lexus checked engine light by going to the Clear Codes menu.

Fault codes are only the starting point.

While they often give you an excellent idea of what is wrong, we recommend having a professional car mechanic properly diagnose the check engine light before replacing any parts.

Lexus Check Engine Light Flashing On and Off

lexus check engine system check flashing

Lexus check engine light will start to flash if one or more cylinders are no longer working properly. This could be caused due to bad spark plugs; a fuel injector is defective, a mass airflow sensor, blown head gasket, fuel issue, clogged catalytic converter.

Flashing Lexus check engine light means an engine misfire, which is a serious issue and needs to be addressed immediately.

Please think of the flashing light as a warning sign that you need to figure out the cause immediately and fix it.

Do not drive your Lexus if the check engine light is flashing, or you will cause damage to the engine and catalytic converter.

Check Engine, VSC, Trac Off Warning Lights On

lexus vsc trac off lights on

Check Engine, VSC, Traction lights stay on after you start your Lexus; the first thing you should do is tighten the gas cap.

A loose gas cap or a damaged gas cap seal is often what causes those lights to come on simultaneously.

If tightening or replacing the gas cap does not fix the problem, use an OBD2 scanner to read the codes.

Should I keep driving if my Lexus check engine light comes on?

As the check engine light will not tell much, deciding on whether you should continue your trip or not might seem difficult.

Observe how your car behaves, and look for symptoms such as:

  • Rough running

  • Engine misfire or juddering

  • Lack of power

  • Poor throttle response

  • Unusual sounds

  • Smoke from the exhaust

  • Overheating

Any of these symptoms indicate that the engine in your Lexus is not performing as it should.

Start looking for a safe place to stop, as driving like this could easily cause irreversible engine damage. 

Do not drive the vehicle if you notice performance issues, overheating, or engine shaking.

Driving your Lexus with these systems can cause expensive engine problems.

Frequently Asked Questions

How serious is a Lexus check engine light?

Some people may drive miles and miles with the check engine light on; however, that's not a good idea.

Although your Lexus check engine light can be triggered by something as simple as a loose gas cap, it can also indicate a more dangerous engine problem, emissions, and even transmission problem.

It's important to take the time to find out what's going on.

How is the Lexus check engine light diagnosis?

You'll need to read the codes with an OBD2 scanner or take the vehicle to a professional, who will hook up a diagnostic tool to read what has been detected. The tool will give a reading of one or several different codes that could be a possible issue.

 How often does the check engine light come on?

Lexus vehicles are designed to be above average in performance and durability. However, that doesn't mean that they will never have any issues. The check engine light could come on at any time, and there is no telling how often it could happen. But if you take regular care of your car and get routine checkups, it should help keep your car functioning properly and reduce the risk of the light being triggered.

 Can I still drive my car if the check engine light is on?to getto get

The answer to that question is maybe. The light may be triggered by a faulty sensor, which means nothing is really wrong with your car. Or a bigger, more serious issue could trigger it. The problem is that without a professional diagnosis, it's hard to tell which one it is. To protect your safety and the safety of others on the road, it's best from getting the vehicle checked as soon as possible and avoid driving while the light is on.

Conclusion

The Lexus check engine light has a myriad of different causes and meanings. Lexus cars and SUVs trigger other warning lights such as VSC, Traction Control, and other warning lights when the CEL comes on. We recommend that you address the check engine light first, as that will often reset the other warning light.

As with any car, it could indicate a severe problem, or it could just be a faulty sensor. Either way, you must get your vehicle diagnosed as soon as possible to see what the issue is.

Hopefully, after reading this article, you feel more comfortable understanding why your check engine light is on and what to do about it.

In this guide, you learned about common problems that cause the Lexus check engine light to come on. You will also learn how to read Lexus Diagnostic Trouble Codes (DTC) yourself using an OBD2 scanner. This guide applies to all 1996 and newer Lexus vehicles, including ES, LS, SC, RX models.

By YOUCANIC Automotive Experts
Nov 2020

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Lexus Check Engine Light Troubleshooting Guide In this guide, you will learn about the Lexus check engine light, symptoms, common problems, and how to read the codes via the OBD-II port.  In case there are engine or emission-related problems, a yellow check engine or "service engine soon" light will illuminate on your dashboard.