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Discussion Starter #1
Hey, new to the forum. Recently purchased 2003 Dodge Ram, 5 speed with the 4.7. 137,000 miles. There were no codes pending or stored prior to purchasing couple of weeks ago, runs strong.

1st, the low fuel light never came on and I assumed I had gas, but it wouldn't start. I put in a gallon and drove to the gas station, logged 385 miles on the tank.

2nd, I have 26 gallon tank but it allowed me to fill over 25 gallons of gas (should have stopped @ 22 I assume)

3rd, Check engine light came on P0420 after the driving for a while.

I am guessing bad fuel pump (?), bad sending unit (?) or something, need help narrowing these things down.

Thanks
 

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Well, I completed a full inspection of my exhaust system and found a few interesting things. #1 - 2003 Ram 1500 should have 2 cats and 4 o2 sensors, but my truck seems to be an early model 03 (March build) and has 1 catalytic convertor and 2 02 sensors.

#2 the cat is not OEM, it is a replacement by the 1st owner and was a cut and weld. Used car dealer doesn't seem to have a clue of the history (typical).

My gut feeling is replace the 02 sensors 1st then worry about the cat later. I won't have another emission test in GA due until late 2015, so I have time.

Anyone have any objections to this course of action or am I wasting my time and should re-replace the catalytic convertor?

Your thoughts appreciated.
 

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Dodge Ram normally has a Build Year of July of one year through June of the next year
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P0420 Dodge - Catalyst System Efficiency Bank 1

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)

Tech notes

As the code description implies the P0420 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 P0420 code is combined with other codes, try fixing the other codes first.

When is the code detected?

- Three way catalytic converter Bank 1 does not operate properly.
- Three way catalyst converter Bank 1 does not have enough oxygen storage capacity.

Possible symptoms

- Engine Light ON (or Service Engine Soon Warning Light)

P0420 Dodge Description


The Engine Control Module (ECM) monitors the switching frequency ratio of heated oxygen sensors 1 (front O2 sensor) and heated oxygen sensors 2 (rear O2 sensor).

A three way catalyst converter (Manifold) with high oxygen storage capacity will indicate a low switching frequency of heated oxygen sensor 2. As oxygen storage capacity decreases, the heated oxygen sensor 2 switching frequency will increase.

When the frequency ratio of heated oxygen sensors 1 and 2 approaches a specified limit value, the three way catalyst malfunction is diagnosed.

See diagram at
http://engine-codes.com/p0420_dodge.html#ixzz37TKDYyhI
 

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Ok, sounds good. I like to focus on the things I can do myself, change the plugs and the 02 sensors then wait and see.

Then, take it to the muffler shop and replace the cat if a no go.

About the build date that is what I assumed from the door sticker,

 

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Odly enough, and maybe unrelated, I ran a bottle of techron in the tank and the light hasn't come back yet. Fixed? probably not, but at least it's not annoying me right now.

One thing after reading the service manual , it talks about 2 different Oxygen Sensor packages on the 2003 ram.

Federal vs California. Federal is just 2 O2 sensors and one Cat. But California is 4 sensors and 2 Cats. While the 2003 models are a dying breed, it is nice to know I'm not crazy about the setup.

Federal Emission Packages :Two sensors are used: upstream (referred to as 1/1) and downstream (referred to as 1/2). With this emission package, the upstream sensor (1/1) is located just before the main catalytic convertor. The downstream sensor (1/2) is located just after the main catalytic convertor.

California Emission Packages:
On this emissions package, 4 sensors are used: 2 upstream (referred to as 1/1 and 2/1) and 2 downstream (referred to as 1/2 and 2/2). With this emission package, the right upstream sensor (2/1) is located in the right exhaust downpipe just before the mini-catalytic convertor. The left upstream sensor (1/1) is located in the left exhaust downpipe just before the mini-catalytic convertor. The right downstream sensor (2/2) is located in the right exhaust downpipe just after the mini-catalytic convertor, and before the main catalytic convertor. The left downstream sensor (1/2) is located in the left exhaust downpipe just after the mini-catalytic convertor, and before the main catalytic convertor
 

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Discussion Starter #6
Learned a few things about gas

Well, since this debacle started I have observed a few things. I was cheap and loved to use Kroger gas. Kroger gas doesn't have detergents. It isn't Top Tier. http://www.toptiergas.com/

The more I use Chevron and techron, the longer I have gotten between codes. I even used the lacquer thinner trick and things have calmed down dramatically. ( https://www.youtube.com/watch?v=5icTmYItwiE )

I even replaced both my 02 sensors, but honestly after the techron and lacquer thinner trick my scanner has shown I'm ready for emission testing. I have taken my truck on the highway and burned alot of gas at high speeds, just trying to get my cat operating at optimum efficiency.

Right now, I have yet to replace my catalytic convertor, but from my scan tool everything seems to be functioning normal for now, no codes.

I believe this all started with Kroger gas. Not to knock Kroger, love to shop there but their gas lacks detergents like Chevron. And, yes, they allow you add the detergent at the pump (Additech I believe) so you can get it added while pumping, but the more Chevron I use, the better it works.

So much ado about nothing more than cheap gas :shy:
 
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