Q: My car shows a P0420 code and the engine coolant temperature reading (via torque pro app and elm327 Bluetooth reader) stayed at 84.2 degrees

asked by on November 06, 2016

How low can the ect read, I'm pretty sure a faulty ect is my issue that or an o2 sensor, because the cataylist should still be fine with the mileage on this car, but I have not ruled it out completely, car was parked for roughly 5 hrs before checking then I first done KOE to get code, cleared and monitored PIDs with engine running approximately 5 min (I feel the owner of the car has been swindled by a shop) Thanks

My car has 90000 miles.
My car has an automatic transmission.

Hi there - "boundary measured engine temperature," or the lowest temp reading a sensor can transmit, can be different based on each temperature sensor. The issue here is what is the true engine temperature? Is the thermostat getting the engine up to its design temperature (something near 205 degrees Fahrenheit/100 Centigrade). Can you cross-check the engine temperature with a laser thermometer, cockpit temperature gauge (middle of the gauge usually), or other measuring device? If the engine is truly coming up to 200 degrees (F) or so, then yes, the ECT can read "low" to the computer, causing rich mixture running. This could cause a low catalytic converter efficiency problem if the engine has run rich for a while.

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

What others are asking

I drive a 2006 Suzuki forenza manual, whenever I break my RPM goes up and I get a screeching noise slowing down.

Hello, thank you for writing in. There have been many similar complaints about this model and others. The issue may be caused by several different components, and you will want to check into each of them. To begin, you will...

Replace ECU or torque converter.

You are correct about needing an ECU and possible a new transmission. Your vehicle may be covered by a recall from the manufacturer. The recall is T-CP-2TC. You will need to contact your dealer to see if your VIN is...

My RPM is very erratic and the engine surges on my 2006 Hyundai Elantra

Hello. I would usually start by scanning the computer for codes to see if anything comes up. If there are no codes then I would check and see if there are any sensors that are not reading correctly. It sounds...

Sqeaking in the rear

Hi there. The problem you're describing sounds awfully similar to an issue with the wheel bearings to me. The wheel bearings allow your free floating rear tires (on the Dodge Caliber) to ride without restriction. However, when you hear a...

Having problems with door locks on 08 Cadillac CTS. Driver side door especially and will not lock or unlock with key. Others loc

This is often related to a malfunctioning door lock actuator, a blown fuse or a faulty power door lock switch. When you use the door lock switch in the car it sends a signal to a relay which then activates...

Car leaking coolant from flange.

You may need to have the radiator hose clamp replaced. I have had problems with the spring type connector on the hose. You should change them out to the screw on type clamp. I would recommend having a technician from...

My car wont start, ECM issue

Hi. I think the best thing to do with this situation is to replace the motor and get the proper radiator for the car. If the ECM has a fault or has gone bad completely the ECM will need to...

I have a 2011 ford focus just replaced the roll pin inside the manual transmission. dropped a head of a bolt inside cant get out

The "technique to get it out" depends on exactly where it is. There is sometimes a possibility of a foreign item safely staying in place but admittedly in a transmission that is a speculative proposition. At any rate, there are...

My Check Engine Light is on - code P0430

Hi there. If you are getting this code along with a loss of power, it usually means that the catalytic converter is failing. When it fails internally it begins to clog the exhaust which will cause the lack of power....

Related articles

Top 10 Used Cars to Avoid
Used car reviews can highlight poor performance, bad design, and low quality. The Suzuki XL-7 is the number one used car to avoid.
A Buyer’s Guide to the 2012 Suzuki SX4
The The 2012 Suzuki SX4 delivers all-wheel drive in a compact hatch, and provides plenty of space and features considering its ultra-low price tag. While there are plenty of updated options available in this vehicle class, the SX4 Crossover model...
How to Replace a Coolant Level Sensor
Coolant level sensors are faulty if the coolant level sensor light stays on extensively or the engine overheats without the light coming on.