Hey guys, the engine light on my 04 3.7 came on recently and I'm not sure why. Looking for some suggestions....All I know is that I recently ran some cheap fuel injector cleaner. I also know that recently Ive noticed the engine a little rough on start up. Not sure if that has anything to do with it. Another bit of info is that my last tank of gas I got only 11 mpg (16 to 19 normal), but im not sure how long the light has been on. I have my wheel tilted up and it blocks it. Other than that the truck is running fine. Thanks for any advice

 

It's probably not likely at all that the FI cleaner triggered the CEL. At most it would possibly have caused bad gas mileage. It may or may not have caused the rough idle. Even cheap FI cleaners just get burned up like gas does, all the cheap ones are is mostly kerosene but sometimes a tank of gas with FI cleaner will have less gas mileage than a tank without it. You need to read the code and find out why the CEL is on. If you don't have a code reader most parts stores will read it for you for free or let you borrow their code reader to use in their parking lot. Then post here or check the CEL code lists up in the FAQ. Then you will have a better idea of what is going on and where to start to fix it.

Jimmy

 

grab the OBD scanner ant let us know the codes. Do a base line on the engine to make sure the basic engine stuff is all good plugs/cap/rotor/wires/air filter etc etc .

 

Thanks for the advice. I will try and get the code/codes. Maybe I will try autozone. Does anybody know where the code reader hooks up to on the 3.7 V6?

 

on the left side under the dash by the ebrake release the is a plug that it plugs in to there

 

Thanks again for the great advice. I went to Autozone and I got a code: P0456. "evap emission control system leak". It said it's a "very small leak". Does anyone have any experience with this? I read on another site that it could be a bad gas cap seal. I guess I'll try that first. If it is that and I fix it, will the engine light turn off by itself? How will i know it's fixed?

 

Try a new gas cap first, it is the easiest thing to try. There are a lot of different reasons for the evap leak codes, a bad gas cap is one of them. You can put on a new cap and get the Autozone guy to clear the code with their code reader, the CEL will not go out by itself. Then drive the truck for a few days and see if the CEL comes back on. If it stays out you are OK, if it comes back on you need to keep looking for the cause of the problem.

Also check the hoses at the evap emissions canister. It is located under the truck, driver's side in front of the gas tank. The rubber hoses on it are known to crack and split open and cause evap leak codes to be set.

Jimmy

 

You can clear the code by removing just the neg cable from battery for a short time.
Afterwards, the truck must be driven around 50 miles to see if code pops again.
Theres a tool called ODB Scan2, rides in the truck connected to that port. It will give you realtime data from the trucks ecm while you drive it. It also has a code reader.
Water temp, engine temp, rpm, gas mileage, etc...... You can get code definitions online as well as a Chiltons.
Worth the money IMO.

luck

 

ok, I went under the truck and checked the hoses. They all seemed fine unless there is a super fine split in one, which I doubt. I guess I am going to trouble shoot with a new gas cap even though mine seems fine. What a PITA. I think i'll go back to Autozone to have the code cleared. I don't really like the idea of disconnecting the battery. Does anyone know if I can get a gas cap at Autozone or another parts store? I avoid stealerships at all costs.

I do like the idea of maybe owning a code reader. Seeing your current mpg's would be cool (or sickening, whichever way you look at it)

 

Yes Auto Zone, Advance Auto Parts and most any parts store should have a gas cap for your truck. They sell code readers there too if you need to buy one. You could probably save a good chunk of cash if you bought it online from Advance and used one of their online discount codes and picked it up in a local store.

Hopefully all you need is a new gas cap and to reset the PCM. You can do a hard reset on the PCM yourself by disconnecting the negative battery cable and holding the ignition key in the "Start" position for about 20 seconds. That will clear the CEL, but I believe the trouble code still remains in the history on the PCM. To clear it completely you need a code reader that can communicate with the PCM via the OBD diagnostic port, or the Dodge dealer can do it with their DRB-3 diagnostic tool.

If the CEL comes back on you may need to do further investigation on your truck to find the cause. If you have a leak in the evap system somewhere it could be as simple as a bad gas cap or a split/cracked evap system hose. It could also be a failed evap system component like the Emissions Leak Detection Pump, the Evap Purge Solenoid or the charcoal canister under the truck could be bad. Usually what causes problems in the canister is when people fill up the tank and then keep goosing the gas nozzle to put as much gas as the tank will absolutely hold, or they do it to round up the purchase total amount on the pump, or both. The fuel and evap system are not designed to be topped off and have that much excess fuel and eventually the excess gas fumes cause the charcoal canister to go bad.

The dealership or a good independent garage can do a smoke test where they inject the emissions system with smoke from a machine. The smoke comes out of the evap hoses or where ever the leak is and shows the tech what the problem is. It is kind of like when you put a flat tire in water and let the air bubbles show you where the nail or puncture hole is.

Jimmy