Q: Car idles and multiple trouble codes are triggered

asked by on October 19, 2016

My Lexus only idles when it's not moving and car is on. I had put in New spark plugs on the left side of the motor. But car still idles. The codes I get are p0301,p0300,p0303,p0172,p0139 and C1201. I have not found and vacuum leaks and all plugs are connected. I can't figure what the problem is?

My car has 143325 miles.
My car has an automatic transmission.

Check Engine Light is on Inspection $94.99 - $114.99 Get a Quote
Spark Plugs Replacement $113.11 - $716.47 Get a Quote

Hi there. If this vehicle is having an idle concern, I have to ask if you may be having a stumble or stall issue when coming to a stop.

If so, your vehicle may be covered under a special service campaign for engine misfire due to excessive carbon buildup in the quench zone of the combustion chamber. However, all of the spark plugs need to have been replaced and with the correct type, iridium, before they will even consider it; thus relieving the misfire codes.

As for the later 3 codes stored, these could be related to the fuel pressure sensor on the high pressure fuel rails and should be inspected by a qualified technician as this system could have upwards of 1500psi of fuel pressure in the rails.

The pressure sensor has 3 wires, one of which is blue and is the VC (vehicle communication) wire that carries the 5 volt reference. If this signal goes open, it can set the additional codes or a combination of them. If this circuit becomes shorted, then communication shuts down and the vehicle usually will not start.

YourMechanic has several available technicians that can assist you with a Check Engine Light inspection and can perform a spark plug replacement, or any other repairs that are needed.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing


Experienced Mechanic?

Earn up to $70/hr

What others are asking

Advice on having the transmission flushed
Hello there, changing the transmission fluid (https://www.yourmechanic.com/article/how-long-does-transmission-fluid-last) at the recommended service intervals helps the transmission last longer and reduces chances of faults down the line. Mercedes recommends a transmission fluid service at 40,000 miles as part of the 40,000 mileage...
Car takes 2-3 tries before starting
You will need to have a mechanic diagnose both the codes (https://www.yourmechanic.com/services/check-engine-light-is-on-inspection) to see if you have a problem with both sensors or have a problem with the timing of the engine being out of position. The codes suggest that...
Power steering issue
If the pump is losing its pressure, then output could be the cause of the steering and noise issue. You would need to have the power steering pump tested to make sure the pump is supplying the proper pressure in...
Sounds like a small fan on engine when car off, not radiator fans.
Hi, thanks for writing in. The noise you are hearing is the emission control system performing a system test of the fuel tank vapor system. The system should run the test in less than ten minutes. If the battery cannot...
Location of the door actuator that controls the defrost floor and vents. Controls where the air goes through.
I will tell you where it is located, but it requires the removal of the glove box to access it. In addition, there are
Sometimes, the lower gears are slow to shift (high RPM) when starting to drive from being stopped or almost stop 2012 Ford Escape
Hi there, The "slow shift (https://www.yourmechanic.com/services/not-able-to-change-gears-inspection)" symptoms you are experiencing may be caused by a malfunctioning transmission internal speed sensor, or by a failing throttle position sensor (which communicates with the transmission controller). Either of these could cause the symptoms...
Engine malfunctune, power steering lights on
Hello, thank you for writing in. The power steering system is driven off of the power from the engine. Without proper engine function, the power steering system will not work correctly. The adverse is true as well. A failing power...
Backfiring and sluggish
It sounds like you may have a misfire or a timing problem causing the motor to backfire. Engine misfires can be caused by many different problems and are generally caused by either a spark or fuel issue or in some...
I have a 2011 Audi A5 quatro 2.0T, it has 55K miles. Needs an oil change and turn off the service message.
Hello. You are right. Your vehicle does need these filters changed and the oil changed during this service. It will also need to have a complete vehicle inspection as part of this service. A certified mechanic from YourMechanic can come...

Related articles

A Buyer’s Guide to the 2012 Lexus RX450H
More More and more auto manufacturers are offering hybrid versions of their compact and mid-size sedans, but a surprisingly small number of them are doing the same for their smaller trucks, SUVs and crossover utility vehicles (CUVs). Among those forward-thinking...
A Buyer's Guide to the 2012 Lexus GS450h
The The 2012 Lexus GS450h is for those who want to drive a hybrid, but would prefer to still enjoy a luxurious and safe ride. Fortunately, as this sedan proves, going the hybrid route doesn’t have to mean you lose...
The Best Used Cars to Buy to Maximize Resale Value
A A car is not an investment. An investment, by definition, increases in value. A car is a necessary purchase, and it will never appreciate in value, with the possible exception of classics and antiques. So, as a used car...