2001 Cadillac Seville P300 & P306

Misfires at no. 6 cylinder-check the spark/compresion and injector for #6 P0300 is normally caused by vacuum leaks an bad fuel.

Engine misfiring by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.

P0300 indicates a general misfire is detected, the 306 is more specific to cylinder #6. Is there a misfire felt? One thing you could do is swap the coils from bank to bank, if you now have P0305, you need a coil pack. It is possible that one coil out of the four could fail, they are just packed into one convenient housing.

A catalytic converter is not going to cause a single cylinder misfire, and the smell may be due to the unburned fuel in the cat, from a misfiring cylinder. Like I stated in my previous post, you can swap the coils. The only difference is one is black, and one is silver. Can't explain the $10 difference. A misfiring cylinder can damage the cat over time, you would get a code as a result, I believe a P0420 or 430.

There are some things the car's onboards can't do, and there are some things a generic scanner can't do. First, on a factory scanner, there is a category called freeze frame/failure records, and 'not ran since cleared. Sometimes there are codes that relate to a fault that can be discovered in these areas that you may not know even exist. Also, on a factory scan tool you can view misfire data in counts or on a bar graph. Earlier vehicles had a bit more comprehensive onboard system that you could perform output cycling, view inputs, outputs and data. Cadillac has transitioned to not even having the onboard option after about 2004 vehicles. The rotten eggs is the sulphur by-product from the chemical reaction in the converter. As I always knew it, the stronger the sulphur smell, the more unburned fuel that has entered the converter.

The location of #6 is on the front bank, those are the even cylinders 2-4-6-8. The way GM has done it, and I believe it continues this way, Is bank 1 usually refers to the bank with cylinder #1, and bank 2 with #2. And I believe it is still odd on one bank, and even on the other.

If it were my money to spend, and the check engine light was currently not on, I would wait till it comes on and go from there. It sounds like the running is not that bad. It is possible that internal circuitry in the module is causing the p0306 without there being a misfire. Did you swap the coils by chance, if the p0306 comes back, I would swap the coils, clear the codes, drive it until it comes back. If it comes back with a p0305, then replace the silver coil and return them to there original locations.

As far as the smell, I would not replace the converter. The only time I would recommend replacement of a converter on a vehicle with catalyst monitoring(like yours) is when the check engine light comes on. Here is some info on the sulphur issue, one bulletin is rather old, and one is new, but they both say about the same.

#31-66-02: EXHAUST ODOR AND OTHER FUEL RELATED CONCERNS - (Nov 18, 1993)

"GM OF CANADA" AND "NAES" DEALERS ARE NOT AUTHORIZED TO UTILIZE THIS SERVICE BULLETIN.

SUBJECT: EXHAUST ODOR AND OTHER FUEL RELATED CONCERNS (USE KNOWN GOOD QUALITY FUEL)

MODELS: 1990-1993 CADILLAC DEVILLE, FLEETWOOD, SIXTY SPECIAL (FWD) 1990-1993 CADILLAC ALLANTE 1990-1994 CADILLAC ELDORADO, SEVILLE 1994 CADILLAC DEVILLE, DEVILLE CONCOURS (WITH 4.5L, 4.6L OR 4.9L ENGINES)

CONDITION:

SOME 1990-1994 VEHICLES THAT REQUIRE PREMIUM FUEL USAGE MAY EXPERIENCE ONE OR MORE OF THE FOLLOWING INTERMITTENT DRIVEABILITY CONDITIONS:

O EXHAUST ROTTEN EGG ODOR OR SULFUR ODOR. O POOR COLD ENGINE OPERATION: NO START/HARD START, START/STALL AT IDLE. O HOT RESTART PROBLEMS. O ROUGH/MISS AT IDLE. O HESITATION AND/OR LACK OF POWER. O DETONATION.

CAUSE:

THESE CONDITIONS MAY OCCUR DUE TO THE FUEL IN THE VEHICLE. POOR FUEL QUALITY HAS BEEN RECOGNIZED TO CAUSE ANY OF THE CONDITIONS LISTED ABOVE. HIGH SULFUR CONTENT FUEL HAS BEEN RECOGNIZED TO CAUSE EXHAUST ROTTEN EGG ODOR OR SULFUR ODOR CONDITIONS. OXYGENATED FUELS WHICH ARE USED IN MANY AREAS OF THE COUNTRY MAY HAVE A DISTINCTIVE ODOR. THIS IS CONSIDERED NORMAL, AND IS NOT RELATED TO THE EXHAUST "ROTTEN EGG" ODOR.

THE OBJECTIVE OF OXYGENATED FUELS IS TO REDUCE TAIL PIPE EMISSIONS OF CARBON MONOXIDE. CARBON MONOXIDE IN THE ATMOSPHERE, ESPECIALLY DURING WINTER MONTHS WHEN IT IS AT ITS HIGHEST LEVELS, CAN AFFECT THE HEALTH OF PEOPLE WITH HEART DISEASE AND RESPIRATORY PROBLEMS. THE OXYGENATED FUELS CONTAIN OXYGEN COMPOUNDS THAT MAKE COMBUSTION MORE EFFICIENT WHILE LOWERING CARBON MONOXIDE LEVELS IN THE ATOMSPHERE.

THE FEDERAL CLEAN AIR ACT AMENDMENT OF 1990 REQUIRES THE USE OF OXYGENATED FUEL IN NEARLY ALL CARBON MONOXIDE NON-ATTAINMENT AREAS IN THE UNITED STATES. THE PROGRAM BEGAN LAST WINTER IN CERTAIN NON-ATTAINMENT AREAS. THESE REGULATIONS WILL CONTINUE IN FUTURE YEARS WITH WINTERTIME FUEL STARTING, IN SOME CASES, AS EARLY AS THE BEGINNING OF SEPTEMBER AND ENDING AS LATE AS APRIL DEPENDING UPON THE AREA OF THE COUNTRY.

#09-06-05-001: Information on Sulfur Odor from Exhaust - (Jan 30, 2009)

Subject: Information on Sulfur Odor from Exhaust

Models: 2007-2010 GM Passenger Cars and Light Duty Trucks (Including Saturn)

2007-2010 HUMMER H2, H3

2007-2010 Saab 9-7X

with Gasoline-Powered Engines

Important: This bulletin is not applicable to vehicles operating in Canada on Canadian sourced fuels. Canadian regulations limit the amount of sulfur in gasoline to 80 PPM or less for all gasoline marketed in Canada with no exemptions.

Federal regulations limit the amount of sulfur in gasoline to 80 PPM (some states have lower limits; for example, California's limit is 30 PPM). The federal exception to this rule is an allowance for qualifying small refineries that permits up to 450 PPM until January 1, 2011. Sulfur odor in exhaust from vehicles equipped with gasoline engines is caused by excess sulfur in the gasoline and it cannot be eliminated unless the source of the sulfur is eliminated.

Important : Replacement of catalytic converters for this condition is not an appropriate repair and will not correct the condition by itself.

Do This
Don't Do This

Change brands of gasoline.
DO NOT replace the catalytic converter.

Customers with vehicles that exhibit this condition should be advised of the information in this bulletin and be asked to switch the brand of gasoline that they are using. In most cases, this will result in elimination of the sulfur odor by the time one tank full of gasoline is consumed if the gasoline that was added is within the 80 PPM federal limit.

In order for the odor to be eliminated. Two things must occur. First, the gasoline added to the vehicle must be at or below the federal 80 PPM limit. Secondly, the vehicle must have run long enough to have consumed one tank of fuel containing a sulfur content of 80 PPM or less.

Although there is no way for a dealership to easily measure the amount of sulfur in gasoline, it's a good practice when asked for a recommended brand of gasoline to recommend any of the Top Tier Detergent Gasoline Brands. Although Top Tier brands have not demonstrated that they contain a lower sulfur content than other brands, their detergent additive package makes them a preferred choice when choosing a brand of gasoline for your vehicle. A complete list of Top Tier Brands can be found in Corporate Bulletin Number 04-06-04-047H (in Canada, refer to Corporate Bulletin Number 05-06-04- 022E) or by accessing the website www. Toptiergas. Com.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

The codes are generic communications type codes. Initially, a few questions, Is it a factory moonroof. Does the doorlocks, trunk and fuel door just not operate from the keyless transmitter? Often times when the trunk and fuel door are coupled together, I have to ask if you've checked your valet switch in the Glove box?

As near as I can tell, the problems are unrelated. For the moonroof, The RAP fuse supplies power to the RAP relay and to the sunroof module through the relay. The relay is controlled by the rear integration module. The sunroof module is grounded at G401 which is a splice pack at the rh rear corner in the trunk. For the roof, you would need o verify power on pin A of connector C1, and ground at pin D of C1, C1 is a four pin black connector. If you have power and ground, you could have a faulty module(if it does not slide or vent), or an applicable switch. The BODY fuse in the rear fuse block controls the tank release and trunk release relays. The relays are controlled by the RIM. If this happened all of a sudden, try disconnecting the battery cables and shorting them together for a minute or so. You could have a logic lock type of fault.

Trunk water leaks are not uncommon on this body style. It is possible that the moisture has caused the problem, but not definate. Did you disconnect and short the cables together?

No recall on water leaks. Disconnect and short the battery cables together.