check engine light code

[ANNAOSSENFORT]

The check engine light has been on on my '99 Miata for more than a year. The guy at the Shell station was nice enough to check the code for me, but the dealer won't tell us what the code means. Does anyone out there know what P1135 error code indicates? Much appreciated. -- Anna

[ANNAOSSENFORT]

I'm insanely proud to report that I answered my own question. And I want to turn everyone else on to the way I did it: If you go to www.obdii.com/codes.asp, you can enter the make of the car and the code (in my case P1135), and it will spit out exactly the cause of the error code. Mine was the heated oxygen sensor. The beauty is that I didn't even have to call the dealer to get this information, and can instead keep in business the handsome, affable Greek guy down at the corner service station! - ako

[zelgini]

I'm also having trouble with the check engine light going on and off - sometimes the engine isn't running well, sometimes it is. The code the service folks get is "random misfire" and can't seem to find the cause of it. Anyone have any clues?

[SOULofMAZDA]

I went to that website and it doesn't offer anything for miata only for domestic cars?

[Sparky Lang]

Originally Posted by zelgini

I'm also having trouble with the check engine light going on and off - sometimes the engine isn't running well, sometimes it is. The code the service folks get is "random misfire" and can't seem to find the cause of it. Anyone have any clues?

What year is your Miata? The 1999-2000's had a batch of bad coil packs (the ignition coils that the spark plugs connect to.) It is easy to replace yourself, but costs about $220. If you let the problem go on too long it will destroy your catalytic converter.

[baxter65]

How does one know what the code is? Does it take a mechanic, diagnostic equipment etc. Sorry - I'm not to savvy with cars, but my engine light goes on for a few days about once a month. So far I have just ignored it because it soon turns itself off again.

[Ken Downs]

My 1999 Miata check engine light stays on all the time. If the code is reset the light stays off for a few days and then returns. Autozone says it is a problem with the EGR valve. I removed the valve to check for carbon build up and clean it. Reset the codes by disconnecting battery. Of course the light came back on after 3 days. But long enough to pass emissions test!! Anyone heard of problems with the EGR? They are $250, I would like to avoid buying a new one. Sometimes the car will idle rough thought it might be related to the coil problem described in the other post. Any connection to the EGR?

[Bill4kath]

I got 2 codes today I just pulled. They are P0303 and P0420. The P0303 says cly. 3 misfire detected. The P0420 says catalyst effeciency below threshold (bank 1). Could this be a bad coil pack and that is what's making the 420 code pop up?

[Sparky Lang]

Bill4, your codes are exactly what happens when the coil pack is failing. If the rough running continues it will wreck the catalyst, that is what causes the P0420 code.

[Sparky Lang]

If changing the plug wires does not fix the problem, you probably need a new coil pack. The part is expensive (around $230) but is not difficult to change. This should fix the misfire problem. However, if the 420 code remains you may need to have the catalyst replaced. Fortunately this is a covered part under the 80,000 mile emissions equipment warranty.

[Bill4kath]

Hey thanks, I did get the coil pack today. Going to install it in a few. Also, thanks for the heads up on the 80,000 mile warranty on the catalyst.

[Bill4kath]

Before I installed the ignition coil pack, I bought a set of NGK wires for it. And, that was the problem. Luckily I was able to returm the coil pack. Thanks for all the help.

[yongsu]

If the coil pack is bad, wouldn't the ecu code show two misfiring codes? Isn't there dual coil on the miatas? I think it is a single unit, but has two coils.

[mazdatech177]

youll get p0300 for a coil going bad, it is a two plugs per coil setup.. when the pcm detects more than 1 misfire it throws a "random misfire" code p0300.

[yongsu]

I have a 99 miata which had to have cat replaced (ECU P0421). Just bought it..... The dealer asked me if I had any misfire problem, which probably caused the cat to go bad. They suggested that I get new coil pack ~$400 replaced. I talked to the previous owner, and he told me that he had problem last year (running really rough) where he had to replace crankcase position sensor ($350). Could CPS have been the problem? Should I be worried and replace the coil pack? I know that 99 supposedly had faulty coil pack, but replacing something that works well for ~400 is stupid. What percentage of the 99 had bad coils? Why isnn't Mazda recalling coil pack like they did with the Protege?