Q: What's at fault, is it my computer module, a bad CAT, or a sensor?

asked by on November 07, 2016

So my pickup has a single straight pipe I keep getting a check engine light that turns on and off when it wants to one week it says bad O2 sensor the next it's something with my CATs (I can read these codes with my programmer) I have a video of it starting on a 40 degree morning and it sounds horrible. I've had people tell me it's my computer module? When it gets cold like in the teens it barely starts.

My car has 119000 miles.
My car has an automatic transmission.

Check Engine Light is on Inspection $94.99 - $114.99 Get a Quote

Hi there. The codes would be helpful and don’t clear them. A sticking O2 sensor can cause drivability issues and set the Check Engine Light. If there is a catalytic converter code, I would focus first on the O2 sensor code and get that corrected and monitor the catalytic converter code to see if it returns. If it returns, then proceed with further diagnosis of the converter code. The ECM being faulty is a possible cause, but without proper inspection I would not recommend replacement.

Starting with diagnosing and correcting the codes is the best route to see if what is setting the codes is also causing the cold start issues. I strongly suggest acquiring a qualified technician to perform an inspection to avoid replacing unnecessary parts. YourMechanic has several available technicians that can assist you with a Check Engine Light inspection at your own location.

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

How do you change from English units to metric units or vice versa?
By default, your car measures everything in English measurements. However, you might prefer to use metric units instead. Changing that is pretty simple. Here’s how to do it: Press the Info button until “Units” is displayed. Press the Reset button...
How do I connect an iPod?
You can connect an iPod to your sound system, so that it plays through the speakers. Doing so only takes a few steps: Open the USB Aux cover on the center console. Connect an iPod cable to both the iPod,...
Shifter won't shift gears
Greetings! What you have described is a common issue that many Dodge Charger owners may face. The problem is likely a worn parking gear shift lock bracket. It is made of plastic, and over time, the plastic will stretch and...
The dome and the rear brake lights are not working.
Hi there. It is very rare that these two circuits affect each other. It can be a failure in the SAM module if both of these problems started at the same time, but most of the time they are separate....
Reverse doesn't work? Could it be solenoid?
Hi there, thanks for writing in. There is a reverse band that will lock the reverse drum to reverse the rotation of the output shaft. You will need to have the transmission tested to see if the band is being...
My car won't start after a break-in & attempted theft.
When someone breaks in the vehicle, the Immobilizer system shows that the doors were locked from the outside. When the doors are ajar from the outside when locked, the security would set so the vehicle could not be stolen. Look...
Easy out snapped off in screw hole
Hi there. I'm not sure how we can help you, as we only work on cars, trucks and SUV's sold in the United States. You might find some tips and ideas on YouTube.com.
Cannot hold rpm in neutral, rpm bounces in rhythm
This may be related to a couple of different possibilities. What you are describing sounds like a dirty or failing idle air control valve. The idle air control valve (https://www.yourmechanic.com/services/idle-control-valve-replacement) monitors the air intake as it is mixed with fuel...
Rough idle after fuel injector swap
Hi Mason. Thanks for sending your question today. Most of the time, when this occurs, it's due to either the replacement injector not being correctly installed or perhaps a secondary or other injector was faulty as well - but not...

Related articles

What Does a Catalytic Converter Do?
The The modern automotive exhaust system is much more advanced than what was available even just a couple of decades ago. After recognizing that the average automobile was one of the primary sources of global pollution, the US government enacted...
P2739 OBD-II Trouble Code: Press Control Solenoid F Control Circuit High
P2739 means a problem was detected with a transmission solenoid usually caused by a failing transmission, low fluid level, or electrical issue.
P2330 OBD-II Trouble Code: Ignition Coil K Primary Control Circuit Low
P2330 means that there is a problem with a primary or secondary circuit of ignition coil K. This is typically due to damaged or frayed wiring.