Lexus Check Engine Light Troubleshooting Guide
Lexus is Toyota’s luxury brand, and as such it inherits it's high-quality and reliability. Yet, as luxury and high-tech come with some added complexity, they are not 100% trouble-free.
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 it will be accompanied with a ‘cruise control’, TRAC Off or a ‘VSC’ light.
In this guide, you will learn about common problems that cause 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.
What does Lexus check engine light mean?
Lexus check engine light means that the On Board Diagnostic (OBD) system has detected a problem. This could be something 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 that you will notice when you Lexus check engine lights 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. Make sure you get it checked as soon as possible.
What to do when your Lexus check engine light comes on?
When your Lexus check engine light comes on, we recommend checking a few basic items before you continue your journey. Do not continue to drive if the check engine light is flashing.
- 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.
- 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.
- Allow the engine to cool down and check the engine coolant level.
- 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.
- Read Lexus engine fault codes using an OBD2 scanner as soon as possible. See instructions below.
How to read Lexus Check Engine Light
In this section, we show you how to read Lexus check engine fault codes (also known as Diagnostic Trouble Codes or DTC) using a generic OBD2 scanner.
- Locate the OBD2 port under the dashboard. Plug in your OBD2 scanner.
- Turn on the ignition but do not start the engine.
- Allow your OBD2 scanner to turn on and communicate with your Lexus.
- 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 Clear Codes menu.
Fault codes are only the starting point. While they often give you a very good idea of what it is wrong, we recommend having a professional car mechanic properly diagnose the check engine light before you replace any parts.
Common causes for Lexus check engine light to be triggered are:
A spark plug that no longer fires is one of the most common problems that triggers 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 recommendation in the owners manual. Typically 120,000 miles.
On older Lexus vehicles that were 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 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 along with codes such as P0300, P0301, P0302, P0303, P0304. But 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 timing of the valve lift. 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, P1351 in addition engine will idle rough and feel underpowered.
Possible solutions will be to clean the VVT valves, replace the cam sensors, replace the OCV solenoid. Here is a video that may help you with this problem.
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.
One that is particularly common on Lexus vehicles is the converter under-heating. A lot of people who have vehicles from the Lexus’ LX 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.
If you have a high-mileage Lexus, it is very likely that you will have a ‘check engine’ light caused by a emission control related problems. 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 much more expensive catalytic converter. Code: P0420 (Catalyst Efficiency Below Threshold)
Oxygen sensor (O2) may fail triggering the 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 is 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. Problem usually lays within the idle air control valve, which gets blocked by dirt, oil or carbon build-up. Use This carb-cleaner to remove the build-up. Code P0505
If you are getting codes that are related to 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 manifest 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 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 to a complete engine failure at highway speeds. Visible symptoms are blue smoke on startup or acceleration, as well as yellow gunk on the oil filler cap. You could also get emission control related codes, such as P0420.
Lexus Check Engine Light Flashing
Lexus check engine light will start to flash if one or more of the cylinders if no longer working properly. This could be caused due to bad spark plugs, a fuel injector is defective, a mass air flow sensor, blown head gasket, fuel issue, clogged catalytic converter.
Flashing Lexus check engine light means that there is an engine misfire which is a serious issue and needs to be addressed immediately. Think of the flashing light as a warning sign that you need to take immediate action to figure out what the cause is 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
Check Engine, VSC, Traction lights stay on after you start your Lexus, the first thing you should do is to tighten the gas cap. A loose gas cap or a damaged gas cap seal is often what causes those lights to come on at the same time.
Should I keep driving if my Lexus check engine light comes on?
As the ‘check engine’ light will not tell much, deciding on whether should you continue your trip or not might seem difficult.
Observe how your car behaves, and look for symptoms such as:
Engine misfire or juddering
Lack of power
Poor throttle response
Smoke from the exhaust
Any of these symptoms indicate that engine in your Lexus is not working as it should.
Start looking for a safe place to stop, as driving like this could easily cause irreversible engine damage. We recommend that you avoid driving 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 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 really going on.
How is the Lexus check engine light diagnoses?
You’ll need read the codes with an OBD2 scanner or take the vehicle to a professional, who will hook up a diagnostic tool to get a reading of what has been detected. The tool will give a reading of one or several different codes that could be the 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?
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 to get the vehicle checked as soon as possible and avoid driving while the light is on.
The Lexus check engine light has a myriad of different causes and meanings. Lexus cars and SUVs are known to 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 well.
As with any car, it could indicate a very serious problem or it could just be a faulty sensor. Either way, it’s crucial that you 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.
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