Question about 1999 Honda Civic

1 Answer

P0420 p1399 Car abruptly began sputtering. Trouble codes p0420 p1399

Posted by on


1 Answer

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points


    An expert that got 20 achievements.


    An expert that got 10 achievements.


    An expert that got 5 achievements.

  • Honda Master
  • 20,706 Answers

99 civic? ever tune it up, or run the cam belt fore ever?
you do now, ignoring the bent, ends in bent valves, right?

which engine option, cylinder count and displacment. USA 1.6L? I-4?

misfiring. ever tune it up this decade? or 60k miles? with cam belt.
1399 is misfire (let me guess, the CEL flashes )
do not skip the belt if due, or you will lunch the engine.

420 is: (ID IGNORE THIS, till the MISFIRE ENDS !!!)
Possible causes
- Three way catalyst converter Bank 1
- Exhaust tube
- Intake air leaks
- Fuel injectors may be faulty
- Fuel injector leaks
- Spark plugs may be faulty
- Improper ignition timing
- Engine Control Module (ECM)

(the bar room answer for 420 is, the CAT is weak, )
the autoshop class>? ASE.. if the cat is or was tortured (misfire)
then fix that first and pray the cat bakes dry and passes 42x codes
if bake many dry, and 420s cleared.
what happens is you overload the CAT with raw fuel, ignore it.
the CEL flashing (USA) means you are KILLING THE CAT.

now we cover, misfire
there are huge possibles.
in a big shop we connect 5 gas to tail and start there .
in a lesser shop, plenty. we check closed loop at idle
if not in closed loop at idle, we fix that first. (easy ,car is parked)
(later closed loop at 40mph light flat cruise, steady right foot) no hills.
Misfire, :
Bad engine, bent a valve> do to ignoring the belt. got vacuum bounce?
bad spark
bad injection rates, or injectors clogged ,dead or weak or leaking.

me, i watch pendings to see of P0301 , to P030x (x is cylinder num)
if the scan tools shows any misfire codes, i do a leak down
on the cylinder that misfires, 300s is random.

lots of ways, EGR stuck open
AFR runing lean, scan too sees that...
AFR stuck rich, same.
the best order is this. (no clues with extra DTCS
compression test. and leak down. if smart.
spark tests.
last fueling, rates, (fails closed loop at idle spark good , engine good.
i do the the injector leak down tests. and balance,

i also do the cAT melted test. cat back pressure test
less that 2psi at 2500rpm.

Posted on Jan 01, 2014


1 Suggested Answer

  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

a 6ya expert can help you resolve that issue over the phone in a minute or two.
best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.

Posted on Jan 02, 2017


Add Your Answer

Uploading: 0%


Complete. Click "Add" to insert your video. Add



Related Questions:

1 Answer

Can catalytic converter cause a PO65O code

Pesky PO420 Codes - Eastern Catalytic
One of the most annoying is the persistent PO420 diagnostic code (Catalyst System ... not only shows its teeth when the catalytic converter is on the blink, but can also be ... Most, if not all, catalytic converter failures are caused by a problem or ...

P0420 Error Code: Catalyst System Efficiency Below ...
Repair information for the OBD-II trouble code P0420 - Catalyst System Efficiency ... If they have failed, it is likely due to something else that caused it to fail. ... the catalytic converter is broken or failed, it may be restricting the exhaust which will ...

explaining trouble codes po420 - po421 - Discount Catalytic ...

Jan 16, 2016 | Cars & Trucks

1 Answer

Car sometimes will not start after sits for a day

Definition of Diagnostic Trouble Code P0420 Category: Powertrain Definition: Catalyst System Efficiency Below Threshold Bank 1Note: This definition of P0420 is applied to all manufacturers

Definition of Diagnostic Trouble Code P0430 Category: Powertrain Definition: Catalyst System Efficiency Below Threshold Bank 2Note: This definition of P0430 is applied to all manufacturers

As the code description implies the P0430 code means that the vehicle's control module has detected that the three-way catalytic converter is not working properly (is not as efficient as the factory is expecting). Replacing the oxygen (O2) sensors may sometimes fix the code, but in most cases the catalytic convert needs to be replaced to fix the problem. If the P0430 code is combined with other codes, try fixing the other codes first.

Jul 11, 2015 | 2006 Toyota Solara

3 Answers

I have a p0420 code on my 2010 Jetta, already changed my 02 sensor. the car has only 70k miles on it, should I change the CAT or look at something else?

I wood look at somin else clear the code if it comes back then we should seewhat we can do as anything Changes since it has been on ? Let me Know thks for your time

May 10, 2015 | 2010 Volkswagen Jetta

1 Answer

Acura TL '99.had an oil leak which was corrected

I do not know what these codes are but as a starting point look them up on a web search

Oct 04, 2014 | 1999 Acura TL

1 Answer

Trouble Code p0420 and p1399

code po420 refers to cat converter system bank1 - efficiency below threshold===causes -- cat converter---wiring---HO2S 2
code p1399 refers to cylinder no 6 misfire===causes --fuel/ ignition---VTEC system---MAP sensor--wiring---mechanical fault.

Dec 31, 2013 | 1999 Honda Civic

1 Answer


P0420 isnt a misfiring code; this code P0420 is refer at Catalyst System Efficiency Below Threshold (Bank 1).

Feel free to contact us if you need additional details to volve it clicking the link.

Oct 24, 2011 | 2002 Volvo S60

3 Answers

Car began sputtering badly, like plugged fuel filter. Replaced but did not fix. Checked injectors by unplugging each one while car was running. Found that the far left one did not change when I unplugged...

Hi, have you tried swapping the ignition wires? If it isn't the injector or plugs, it may be the wire or the valves. If swapping wires doesn't work, run a compression test.

Please see my tip at . These are generic instructions. If you get stuck or need specific instructions for your car, please get back to me with model, year and engine info.

By the way, the code 420 may be caused by the misfire, so don't worry about that unless the code doesn't clear after fixing the misfire.

Apr 10, 2011 | Chevrolet Prizm Cars & Trucks

3 Answers

I had my car inspected and received P0420 code? what does it mean?

P0420 Error Code: Catalyst System Efficiency Below Threshold (Bank 1) Repair information for the OBD-II trouble code P0420 - Catalyst System Efficiency Below Threshold (Bank 1)

Feb 18, 2010 | 2000 Toyota Celica

1 Answer

Repair Codes - B2796, P0750 and P0420.

B2796 is no communication in Immobiliser system, which means you or some one else try to use a key transponder to start the car.
you need some one to clear that code. it doen't affect the car performance.
P0750 is shift Solenoid malfunction, you hsould have engine management light on the dash. this you can call the dealer, I believe this is cover by Toyota service bulletin.
P0420 is O2 oxygen sensors.Toyota has issued a service bulletin regarding the P0420 trouble code that could apply to your vehicle, to be sure if this bulletin applies to your car I will need the VIN# and e-mail to with that information.

May 19, 2009 | 2002 Toyota Camry

Not finding what you are looking for?
1999 Honda Civic Logo

190 people viewed this question

Ask a Question

Usually answered in minutes!

Top Honda Experts


Level 3 Expert

76109 Answers

Colin Stickland
Colin Stickland

Level 3 Expert

22156 Answers

Kevin Daniels

Level 3 Expert

1455 Answers

Are you a Honda Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides