Check Engine - again 2 weeks later.

Check engine light was on. Replaced 02 sensor and had it inspected - it passed. Less than two weeks later, it's on again.

Ideas?

 

What is the code that is causing the light?

 

Autozone guy said EGR valve and then said to try a new gas cap first. Priced the EGR valve at $151.00 and the gas cap at $9.50.

Said it definitely was not another 02 sensor. He said it showed the EGR and then some other codes after that.

He was in favor of the gas cap. I decided against anything at this point.

Suggestions before I buy the gas cap or take it in to the shop?

 

How do you go from 02 sensor to egr to gas cap what is your code ?

 

I would find out the exact code, not just a suggestion on what part may have failed. Then you can Google the code and look for common failures. The most common code for a bad gas cap is P0446. That doesn't mean however that a P0446 HAS to be a bad gas cap.

Looks like just bad luck on having a CEL on 2 weeks later.

 

We need a code to help you. Otherwise a big guessing game.
Yeah,at least it passed inspection before it returned!

 

I can almost guarantee you it's P0401, dealing with the EGR. I can also almost guarantee you you're driving something around a 2001. 1st gens around this year are notorious for that BS P0401 code. I've had mine going on and off for 3 years now and am still getting 20+ MPG. There are threads on here of people completely replacing each part of the EGR system, one by one, and it still comes on. Personally, I think it's a fluke in the 1st gens. Also, it's just some emissions bullcrap, anyway. I don't live in the city, so I don't care. As long as my gas mileage is above 20 MPG, I'm not worrying about it.

Mine comes on about every 100 miles after I reset it and goes back off after about 50 miles. If it doesn't go off, I've got my trusty UltraGauge to turn it off....I do check the UltraGauge every 100 miles or so to make sure that the P0401 is the only engine code on, which (knock on wood) it has been.

 

Since I didn't get the codes, I took it to another Autozone - just to see if anything was different, and here's what came up:

PO441 - evaporative emission control system - incorrect purge. Probable cause - 1. leak in EVAP system 2. Blocked - EVAP purge line 3. Faulty purge

PO442 - evaporative emission control system leak detected - small leak. Probable cause. 1. Faulty fuel cap. 2. EVAP line leakage 3. Pump module failure 4. Canister faulty

PO446 - evaporative emission control system vent control - circuit fault. Probable cause 1. Open or short circuit condition 2. poor electrical connection 3. Faulty CCV vent control solenoid.

This Autozone guy recommended first disconnecting the battery to clear the codes and to add a new gas cap first and see if that took care of the problem.

 

Well, nvm. I was wrong. Unsubscribed lol

 

since gas cap is only $10, may as well start there...before you do the purchase, get your ear next to the cap and remove it right after you have driven awhile, while stopped and engine shut off, if you hear a slight hissing sound when you back off the gas cap, it ain't the cap, move on to something else...

mine throws a P0420 code every once and awhile, so far my gas mileage is superior, so I don't worry too much, ultra gauge reset, usually good to go for thousands of miles before it comes on again...

 

Will check the gas cap first, but....

Tell me what the "ultra guage reset" is....???

 

If you have a ultra gauge you can clear and read your own check engine lights

 

Or get a $10 obdii bluetooth adapter and download torque (free) if you have an android phone. Plus it will hop on the internet and search the codes after it gives you the basic "error with x sensor" info. I have a CEL light about once a day now from a marginal O2 sensor that doesn't heat up as fast as the car wants. Long tube headers, problem will probably never go away. t used to be about every 1000'ish miles, much for frequent now But having to stare at the light or go to the shop every day to get it cleared would drive me insane. Before too long I'll break down and actually swap the sensor, until then torque is my go to

I'd still start with a new gas cap. You have to remember that error codes don't tell you what the problem is, only where its being detected. And that can be pretty far downstream of where the cause actually is. And a $10 fix is better than a $180 one. And I'd rather be out 10 than 180 if the first fix dosn't work.

 

Winner winner, chicken dinner! lmao.

More info on your truck is needed like year, engine, 4wd or 2wd? etc. I would not be surprised if you are a 4wd truck and your evap vent filter is clogged with dirt/mud. Not uncommon at all.

 

Truck is a 2004 regular cab 4X4, 2.7, manual, 4.30 open. Bought it used, and the spare is a mud grabber.

 

I would suggest looking over the entire underhood area around the charcoal canister housing. Check for broken, kinked, damaged vacuum hoses. Check the lines back to the gas tank to see if there are any issues there.

 

That's good advice Bama! I had same thing a few yrs back. Vacum line was culprit!

 

I have had the same evap gas leak now for about a year and a half. Pressure test, smoke test, changed the cannister, gas cap, nothing. I am up for Inspection this month and don't know what to do, the rest of my truck is in excellent shape. 2003, 4 cyl 4x4.

I think it is the damn ethanol in the gas.