Random P0303 & P0171 Codes
 

I have a 09 1500 hemi truck with 160XXX miles on it. For the last 6 months or so I have been getting random P0303 codes. The engine light comes on for a few days then it goes away. Occasionally there will be a P0171 code with the P0303 code but it goes away on its own also?

When I first got the code I swapped the plugs and coil pack from another cylinder and the code stayed on cylinder 3. I have since replaced the 02 sensor but I am still getting these random codes popping up and then going away. I have tried to take it in to my dealership but every time I schedule an appointment the light goes off. They tell me they cant do anything unless the light is on.

Just wondering if any of you guys had similar problems with your truck?

Thanks for your time.

Jerry

I forgot to mention that the truck runs great, no hesitation, plenty of power and the fuel mileage has stayed the same.

I have not had this issue but since you've tried the obvious for code PO303, maybe try to figure out the reason for PO171.

A code P0171 may mean that one or more of the following has happened:

The MAF (Mass Air Flow) Sensor is dirty or faulty Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.

- There could be a vacuum leak downstream of the MAF sensor
- Possible cracked vacuum or PCV line/connection
- Faulty or stuck open PCV valve
- Failed or faulty oxygen sensor (bank 1, sensor 1)
- Sticking/plugged or failed fuel injector
- Low fuel pressure (possible plugged/dirty fuel filter!)
- Exhaust leak between engine and first oxygen sensor

Possible Solutions
- A lot of times, cleaning the MAF sensor and finding/fixing vacuum leaks fix the problem. If you're on a tight budget, start there, but that may not be the fix for certain. So, possible solutions include:
- Clean the MAF sensor. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
- Inspect all vacuum and PCV hoses, replace/repair as required
- Inspect all hoses and connections in the air intake system
- Inspect and/or test the intake manifold gaskets for leakage
- Check for a dirty fuel filter and proper fuel pressure
- Ideally you'll want to monitor short and long term fuel trims using an advanced scan tool
- If you have access, you may want to run a smoke test

Did you ever fix this issue? I am having similar issues.

Sorry I didnt get back to you sooner but I have fixed this problem. I know this is going to sound stupid but do you have any light bulbs that are bad on your truck? The reason I ask is about a year ago I hit my drivers mirror on the side of my garage (dumb ass I know!) it didnt break the mirror but it cracked the lens where the puddle lights and turn signals are at in the mirror. When it rains hard I noticed some water in there and the turn signal would work but the puddle lights would flicker off and on until the water drained and it dried out.

I know you are thinking what does this have to do with these codes but every time I would get one of these codes I had a light bulb out on my truck somewhere. Once it was a tail light, then a fog light, then a front driver side turn signal. I would replace the bulb and the code would go away until the next time it rained hard. So I finally decided to change the puddle light/turn signal on my drivers side mirror and I havent had the codes pop up since. I actually just got back from vacation in the truck and I got the best mileage (17 MPG on the highway) that I have gotten in a long time. The only thing I can think of is maybe with these codes the computer wouldnt let my truck drop to 4 cylinders on the highway??? Anyway, as crazy as this sounds I have not had the check engine light come on once since I fixed the lights!