Gas brand triggering CEL?

[VK56VD]

The vehicle in question is a '99 Nissan Maxima with 126k miles. Since April of 2007 I've been getting a intermittent CEL. Sometimes it lights up and stays on for a while and at times it turns off and re-appears again in a few days. I've had the car scanned and it turns up as a P0430-catalyst efficiency for bank 2 is below threshold. It seems this sensor is after the catalytic converter and monitors the catalytic converter and has no effect on gas mileage. I am planning to change this sensor soon and see if the problem goes away. If replacing the sensor won't cure the problem, I have been told the problem may be the catalytic converter itself. If this is the case, this may be a very costly repair which I will most likely not do but will continue to drive the car as is since there is no effect on driveability or gas mileage.

Here is the interesting part. Several months ago, I began tracking my MPG and the station I fill up at. I always fill this car up with Premium 93 octane since that is what is recommended for optimum performance. (The first owner who drove the car until 103k miles filled it up with regular). I also began documenting when the CEL turns on or off. My gas mileage so far ranges between 26-28 mpg in mixed driving with a very gentle foot. I filled the car up with Shell V Power last time and the light turned off and stayed on until my next fill up which was BP. It seems with BP, Chevron, and Exxon, the CEL is on most of the time but sometimes stays off for a few days. The day I filled up with Shell, the CEL went off and stayed off until I filled up with BP. The same day I filled up with BP, the CEL came on and has been on so far.

What may be causing the gas to contribute to the CEL?

It seems the light is very sensitive to the gas brand used as I usually get the CEL right after a fill up if it has been on or vice versa such as in the case of Shell gas.

On a side note, my best documented mileage has been with Shell V power.

Thanks for all your help in advance!

 

[JasonC]

i doubt that it is gas related. More than likely it is the downstream oxygen sensor getting lazy or the cat is beginning to fail.

 

[moribundman]

Make sure there is no vacuum or exhaust leak, because those can cause that type code. If the engine idles fine I wouldn't be overly worried.

 

[VK56VD]

The engine idles fine. All the maintenance is up to date. When I bought the car with 103k miles on it from the original owner, I received a stack of records with it from day one. It was mostly serviced at the dealership other than oil changes and tires. It had 02 sensors,knock sensors, and coils replaced by Nissan while it was in the possession of the previous owner.

Since I've bought the car, I've replaced the spark plugs to Nissan OEM/NGK Platinums, installed a new Nissan PCV valve, Nissan fuel filter, Nissan Air filter, new pads & rotors-front and rear, flushed the coolant with Nissan Long Life & distilled water, converted the transmission to Mobil 1 ATF Synthetic, converted the PS unit to Mobil1 ATF, ran two treatments of Auto-RX in the engine, began a diet of Pennzoil Platinum 5w30, and flushed the brakes with Valvoline SynPower.

When I look under the car, the muffler is very rusty and most of the protective coating has flaked off but I will not replace it just yet as it seems to still be holding on okay.-Could this be the culprit or is it unlikely?

 

[moribundman]

I'd check for vacuum and exhaust leaks before throwing money at suspect and likely costly components. I also believe a bad coil can trigger that code. I would test all coils. I'd also have the ECM checked (Not at the dealer!).

 

[punisher]

We have been over this before in the forums. Search will likely pull up the last thread on "cat efficiency sensor/P0430 codes.

Sad thing is, if you see that code, and only that code, then it is a darned near certainty that cat will have to be replaced. A bad sensor will not set that code, so you effectively throw money away replacing a cat monitor for a P0430 code. If anything a bad/lazy sensor will miss a faulty cat. Like was mentioned above, ck for any exhaust manifold leaks and if that checks out, get your wallet out. Any missfires, vac leaks, bad coils etc. will set other codes before it will trigger a P0430.

 

[VK56VD]

Ok, how do I check for vacuum, exhaust leaks, and a bad coil?

Wouldn't there be a misfire if one of the coals was bad? The idle is excellent, very smooth, and quiet.

Why would the CAT go bad? Is it possible that it went bad due to the previous owner using regular gas or is it possible that Auto-RX did a cleaning and clogged the CAT?

 

[punisher]

Well, if you have a vac leak, you will sometimes have a rough idle, and lean fuel trims at idle. Exhaust leaks, you listen for. Bad coil, feel for missfires. Like I said above, if you had any of those symptoms on an OBDII vehicle, you will get other codes as well.

Cats just go bad. Sometime through abuse, sometimes just because. Anything is possible. Leaded gas, excessive oil consumption (pre SM days) are two factors that kill their share.

 

[oilyriser]

replace the gas cap. Is it also giving the evap system leak code?

 

[Merkava_4]

You need a scanner hooked up to the diagnostic port to read the operation of the catalytic converter. If this was a GM car, you'd be hooking up a Tech II scanner measuring the parameters (in real time) against the known correct values in the service manual.

Does anyone know what Nissan's equivalent is to the Tech II scanner?

 

[steve20]

doesn't Nissan have a 10 ear 150 K mile warranty on Federal Emissions Equipment?

 

[eljefino]

^ I was wondering that, sometimes its 120k on cats. Check into.

 

[VK56VD]

Nissan CAT warranty is 8 years/80,000 miles.

 

[VK56VD]

When I first bought the car with 103k miles I changed the spark plugs. By accident, I unscrewed a fuel injector in the front of the engine thinking it was access to the front plugs. A day or two later I had a bad misfire and the CEL came on. This was probably due to an old O-ring on the injector that I unscrewed that was very old and could no longer have been re-used. The simple task may have been to buy the cheap O-ring and replace it but I went ahead and replaced the whole fuel injector including the O-ring since it was so easy. All problems went away at this point but shortly after (around 3-7k miles later) the CEl came on with the P0430 code.

Could I have damaged the Cat back then by having a misfire and unburned fuel getting into the Cat system?

 

[VK56VD]

This P0430 code is referring to which sensor below?

B1S1
B1S2
B2S1
B2S2

 

[VK56VD]

B=Bank, S=Sensor

I'm pretty sure it's a Bank 2 sensor but not sure if it's Sensor 1 or 2.

 

[severach]

Originally Posted By: Spartuss
Ok, how do I check for vacuum [leaks]

Spray various tubes and gaskets with carb or brake cleaner. Anywhere you spray that changes the idle indicates that a vacuum leak may be nearby.

Originally Posted By: Merkava_4
Does anyone know what Nissan's equivalent is to the Tech II scanner?


You don't need a fancy scanner for the front and rear oxygen sensors. They are in the generic OBD-II spec so they can be read by any cheapo scanner that shows live data.

Quote:
Nissan CAT warranty is 8 years/80,000 miles.


http://www.epa.gov/oms/consumer/warr95fs.txt

All cat warranties are minimum 80,000 miles by federal law.

Originally Posted By: Spartuss
This P0430 code is referring to which sensor below?


B1S2 unless your car has a dual exhaust.

Bank is left and right as in left and right cylinder bank. Your Nissan should only have one oxygen sensor for the engine so it will be Bank 1. Sensor is front back. B1S1 is the engine oxygen sensor and B1S2 is the converter oxygen sensor. Read this and you'll see why you don't want to just throw a new sensor at the problem.

http://www.aa1car.com/library/o2sensor.htm

 

[VK56VD]

P0430-catalyst efficiency for bank 2 is below threshold.

The above is the definition that AutoZone printed out after scanning the code.

According to Haynes, P0430 Catalysts system fault (left bank).

According to oxygensensors.com there are 4 sensors; B1S1,B1S2,B2S1,B2S2. This car is also California Emissions vehicle.

The Maxima is stock without a dual exhaust. Are you sure it's Bank 1 if the print out is giving me the code as Bank 2?

Thanks a bunch!

 

[severach]

1999 Nissan Maxima SE, GXE, GLE

According to my manual there are two front oxygen sensors "on left & right exhaust manifold." Non CA models have a single rear oxygen sensor "underside of vehicle, rear of catalytic converter" and CA models have two rear oxygen sensors "in exhaust pipe, forward of three-way catalyst."

Your Bank 2 code indicates that your vehicle was once a California resident. Check for:

* Switching frequencies of rear oxygen sensors should be less than 75% of front oxygen sensors. Front sensors should switch more than 5 times in 10 seconds. These can be measured with two volt meters.

* Leaks in exhaust before 3 way catalyst or intake after MAF.

* Spark on all cylinders.

* Injectors must not leak under pressure.

 

[VK56VD]

On another forum, a member wrote that if I do not change the catalyst: "the downside is that the platinum within the cat can start to come apart and your engine can suck it back into the cylinders causing engine failure."

How likely is the above?