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.

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.

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