[My car: 2004 Mazda 3]

So, my wife came home from running some errands and told me the check-engine light was on and that the car was sputtering and felt like it was going to stall while stopped at stop lights. I went to check it out, maybe 5 minutes later, and I took it for a drive... everything seemed fine.

The next day it happened to me. I got to where I was going and let it sit for 10 minutes. The car seemed fine on the drive back home. So, maybe letting it rest, fixes things?

Later in the day I went out and it still seemed fine. I got to where I was going and let it sit for about 40 minutes or so. When I left, it was sputtering again. I drove 10 minutes then decided to try letting it sit a couple minutes in a parking lot.... so I went and parked, sat for a couple minutes and restarted, and it went back to normal for the rest of my drive - about 30 minutes.

Later that day, I left work and it seemed fine for the first 30 minutes or so and then it started sputtering while driving again and really threatening to stall when stopped at the lights. I tried the parking lot trick but it only worked for a couple minute then it went back to sputtering.

Also, at stop lights when it's threatening to stall it smells kinda like rotten eggs.

Sorry for the long story but I want to make sure I put down enough detail.

Anyone have any idea what could be the problem?



Here are the codes:

P2178 - System too rich off idle bank 1

P0335 - Crankshaft position sensor A circuit

P2196 - O2 sensor signal stuck rich bank 1 sensor 1


I took it into the shop and they spent 5 hours troubleshooting the problem and eventually came to the conclusion that the O2 sensor needed replacing. (as Bob Cross suggested)

I got the car back and the next day the same problems started happening again and the check-engine light came back on throwing the following codes:

P2196 - O2 sensor signal stuck rich bank 1 sensor 1

P2188 - System too rich on idle bank 1

It's back in the shop now waiting on a solution.


The car is now fixed - at least it seems to be. I've driven it a few days and the symptoms have not returned.

The fix: the shop found that the MAF sensor was corroded, so they cleaned it up.

  • 2
    You have a check engine light coming on, right? Get the code read so we can speculate on the reason for the code rather than the description above? Dec 21, 2012 at 0:36
  • 1
    I was afraid of that... I'll grab the code and report back.
    – Trev
    Dec 21, 2012 at 0:43
  • Sounds good. I have a suspicion what it might be but it's much easier to avoid throwing parts at the problem if you know what the ECU is complaining about. Dec 21, 2012 at 1:25
  • 1
    @Timo I've updated the question with the codes
    – Trev
    Dec 21, 2012 at 15:52
  • Congrats - glad that things are back in working order.
    – Bob Cross
    Dec 27, 2012 at 17:07

4 Answers 4


Checking a list of TSBs for this set of codes, this looks like a promising candidate:

01-028/04 MAZDA SPECIAL PROGRAM (MSP05) - 2004 MAZDA3 - O2 SENSOR DTC ERROR, P2195 / P2196

From what you describe, a problematic O2 sensor could easily lead to the idling, sputtering and smells that you describe. If the sensor is stuck reading full lean, it's highly likely that the car is pouring far more gas through the injectors than you'd ever want. Has the mileage dropped dramatically since the problem occured?

  • I haven't really driven it that much since the problems started but it does seem like the mileage has dropped.
    – Trev
    Dec 23, 2012 at 12:51
  • See my update... I got the O2 sensor fixed but it doesn't seem to have fixed things. It's back in the shop now.
    – Trev
    Dec 23, 2012 at 12:53
  • @Trev, okay, it looks like replacing the O2 sensor was necessary but not sufficient.
    – Bob Cross
    Dec 23, 2012 at 14:44

I just had these exact symptoms with a 2002 Vauxhall Astra. As well as the Crankshaft Sensor error (and the garage confirmed it had previously thrown out an O2 sensor error).

Mine was the EGR valve, with fuels that use a lot of additives (here in the UK that's 'supermarket fuel') the valve quickly becomes caked in carbon.

The EGR (exhaust gas recirculation) recirculates gases back through the engine before leaving the exhaust in an attempt to lower carbon emissions. 9/10 you can just whip it off and clean it out with carb cleaner and it'll be good for good while longer. However, a lot of people, just take them off the car altogether. You'll often get (very slight) better throttle response in low revs and marginally better MPG (1-3).

If you're engine is quite efficient anyway, removing the EGR will do more good than harm. In the case of my Astra, the ECU would need to be reflashed by the manufacturer to ignore the EGR not being in place (for me that's a P0400).

That said, replacing an EGR if it's easily accessible in the engine bay is a simple job that anyone can do. Take a look at prices online and consider going that route if carb cleaner does work and solves the problem in the meantime.


I have a 2005 Hyundai Elantra, and I was getting OBDII error codes:

P2626 Hyundai - HO2S Pumping Current Trim Circuit/Open Bank 1 Sensor 1 .. and later, I also got

P2196 Hyundai - HO2S Signal Stuck Rich Bank 1 Sensor 1

My car was sputtering, somewhat intermittently. It would intermittently lose power rather suddenly while accelerating. The egine was also cutting out while idling at stop signs/traffic lights.

I found this thread, and I decided to clean the Mass Air Flow sensor first before replacing the O2 sensor. I used CRC Mass Air Flow Sensor Cleaner ($8), and sprayed it all over the exposed wires and plates inside the MAF sensor. It made a notable difference, and the sputtering/stalling seems to be gone. I cleared the OBDII error codes, and so far the O2 sensor codes above have not returned.


Since this was a 2 part fix, I'll add it as the accepted answer, though Bob Cross got half of it correct. I never checked the EGR as DeviateDefiant suggested as it was fixed before getting to it.

The fix:

  1. The O2 sensor was replaced.
  2. The MAF sensor was corroded, so it was cleaned.

I can't help but wonder if we fixed the MAF sensor first if the O2 sensor would've needed replacing. The codes were pointing to the O2 sensor though.... I guess we'll never know. :o)

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