Q: Check Engine Light on - P2187 and P0420 codes

asked by on

About 4 months ago I installed a catless downpipe on my car. I did not get a tune because I was told that I don't need it if I don't want it. My car idles fine but starting it is weird. I've had times where I start the car and it shuts down. I hooked up a code reader to my car and I got the codes p2187(system too lean at Bank 1). Then a evaporative emission system leak(P0442). Also catalyst system efficiency below threshold bank 1(P0420).

My car has 61000 miles.
My car has a manual transmission.

Hello. If I understand correctly, when you say "catless downpipe," you mean that you have installed a pipe without a catalytic converter. If that is the case, you are always going to have the code for catalyst efficiency.

The car has two oxygen sensors, one upstream and one downstream of the catalyst. The controller is looking for a specific oxygen level going in and coming out of the catalyst to indicate that it is doing its job. Without the catalyst, the controller will never see the levels it’s looking for and will always light the CEL.

This won’t effect the way the car runs, but in most states it means you won’t be able to pass inspection. Additionally, if the CEL is always on, it won’t be able to alert you to any new problems. As for the system too lean and EVAP codes, they may have the same cause. It’s possible that you dislodged or damaged a vacuum line while you were doing the work. The resulting vacuum leak could cause the P2187 and if the leak is on the evaporative vent line it could cause the P0442. Look for a damaged or disconnected vacuum hose. If you don’t find one, you may want to enlist the help of a certified technician to diagnose the Check Engine Light and guide you with any repairs needed.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Check Engine Light on - P2187 and P0420 codes

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

Get a quote

What others are asking

Q: I hear a whining sound while I drive my car especially when I accelerate

Hi BJ. Thanks for contacting us today. At first glance, I would assume that the whining noise is coming from your wheel bearings or another driveline component, especially if the noise gets worse as you accelerate. If the noise is...

Q: Q: P0420 code

Honda has a technical service bulletin (TSB) out for this condition. There are 2 possibilities to correct this fault, according to the bulletin: Replace the catalytic converter Software update of the engine computer One last thing...

Q: Can a bad breather filter located under the PCV valve cause my car to turn off after starting it?

No. You should look at the ignition switch not supplying power to the ignition when it is in the run position. This is the most common cause of stall after starting. The ignition switch supplies 12 volt power to the...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...