P0454 Error Code Evaporative...

01 XJ Auto, 4.56 gears, 33" tires, stock engine, Borla header, lifted...

I don't drive this machine much. And, it's gotten chilly here (29-32 deg most mornings), but the Jeep is garaged (not heated though). One morning it threw this code (P0454) and the fancy Harbor Freight OBDII scanner told me (In English, how surprised was I!) that there is a small leak in the Evaporative system. Engine runs fantastic. No stumble or anything abnormal. When the CEL came on, I had just left the driveway and was coasting down a hill.

IIRC, the Evaporative system is the vapor return to the tank, or at least it was on 70's/80's cars.

I have searched the web, but didn't get any useful answers.

Has anyone seen this? I'm almost thinking it might be something stupid like a loose gas cap

-Ron

(Stock engine? Still OEM, then...)

Evap emissions is the system that's supposed to catch fuel vapours (from the tank or wherever else they may be released) and route them to the carbon cannister underhood until they can be purged into the intake. This purgation usually happens continuously when the engine is running, but the carbon cannister catches vapours from accumulated fuel when the engine is not running, then intake vacuum draws them into the intake stream for combustion.

Garaging your vehicle in a cool environment tends to reduce evapourative emissions, so that helps you there.

However, the EVAP system usually consists of:
- Vapour lines between the fuel tank and the carbon cannister
- Vapour lines from the carbon cannister to the intake
- The carbon cannister proper
- A "purge solenoid valve" that cuts off flow OUT of the cannister until intake vacuum is present to collect the vapours properly (it's effectively "sealed" until the engine warms up, as I recall.)

Ergo, you could have a leak anywhere along those lines. Your 2001 should have a "returnless" pressure regulation system, so you likely have only two lines coming from the fuel tank - the pressure line from the pump, and a vapour line at the top (connected, typically, through a "rollover valve" - it's a valve that shuts off if the vehicle is inverted.)

The vapour line is often (but not always!) routed along with the fuel supply line from the tank, but you may have to dig for it after all. The carbon cannister (usually underhood, but not always. And, there may be more than one) should have the line attachments checked. Follow the lines to their various endpoints and visually check integrity - flexible lines ("rubber") should be slightly bent in all directions to make any hidden cracks more apparent.

Also, note that many carbon cannisters will have a fibrous filter on the bottom - this does want replacing at intervals (it's there to allow a flow of fresh air into the cannister when purging fuel vapours.) If it's present and plugged, OBD-II can report an "EVAP System Fault" on you.

The thing I don't like about OBD-II is that, so often, a single DTC can result in you looking for a failure all over the vehicle.

Thanks for the explain Jon. In other words... it works exactly like 70's and 80's Evap systems except that something actually monitors it for leaks.

This thread >> http://www.naxja.org/forum/showthread.php?t=919520
Showed up on the bottom. It's for a P0455 code which is a "Major Leak" in the same system. Good info there also.

-Ron

Just tryin' to help - yeah, it's essentially the same.

And, unless you've done a major engine swap, you can figure that Smog devices are by definition OEM tech, since we aren't allowed to improve smog (USEPA, CalEPA, various Air Quality boards, ...)

On my 2001 I got that code once and found a cracked soft line at the evap canister below the drivers side rear of the Jeep. That code could also be something as mundane as a fuel cap that didn't seat right after your last fill up. Like 5-90 said, that is a pretty generic code.

Last time I got that code I got it in conjunction with a code 1494 which is the leak detection pump located in the engine bay in the very top corner of the passenger side of the bay. You may check the lines near that also.

Check all your lines, take your fuel cap off and re seat it, clear your code, and see if it comes on again.

Funny, at about 170k, mine threw two codes as well. P0441, and P0432.
P0441 Evaporative Emission Control System Incorrect Purge Flow

Causes

A code P0441 could mean one or more of the following has happened:

• Bad vacuum switch
• Broken or damaged EVAP line or canister
• Open in PCM purge command circuit
• Open or short in Voltage feed circuit to Purge Solenoid
• Faulty purge solenoid
• Restriction in EVAP solenoid, line or canister
• Corrosion or resistance in purge connector
• Bad PCM

P0432 Main Catalyst Efficiency Below Threshold (Bank 2)

Causes

Potential causes of a P0432 code include:

• Bad or non-functional catalyst
• Engine operating out of optimal air:fuel ratio

Here is whats funny, there isn't a post Cat O2 sensor, or even the wiring for the O2 sensor. I am in the midst of trying to figure this out, since I will likely get hit to take it for an emission inspection this next year, and I gotta clear the codes to be able to pass. Also bank 2 is the bank not containing Cylinder #1. Funny, it has a single exhaust system. This leads me to believe that the #4-6 O2 sensor might be shot---since there is only supposed to be one catalytic converter. As for the first code above, I need to reexamine the entire vapor recovery system for leaks, and if nothing, replace the purge valve. The light comes on and stays on during the initial key on cycle, prior to me starting it. I do that to verify the fuel pump is working properly.



This site appears to be pretty good at answering OBD II codes as well:


http://www.obd-codes.com/forums/index.php


Jeff

Nice hyjack

5-90, I suggested not OEM because of the header. I am not the Original owner, and the PO liked to putz around (header, mech fan delete, relocated vacuum bottle, and who knows what else...)

Cottontail I cleared the codes before posting yesterday. Since there was only 1 instance indicated by the reader, I figured that clearing and waiting would be more productive than a full blown panic.

So after another 8 starts and 30 miles the code has not returned. Good places to look though! When I get a few moments in a warm garage I'll chase the hoses and look for cracks. There is only 80K on this unit, but cracked hoses come with age. I may even check the gas cap. The tank is getting low, so that may come first

I do appreciate the help guys!

You should probably help ihscoutlover because he sounds like he has a whole mess of problems

WB9YZU said:

Nice hyjack

5-90, I suggested not OEM because of the header. I am not the Original owner, and the PO liked to putz around (header, mech fan delete, relocated vacuum bottle, and who knows what else...)

Cottontail I cleared the codes before posting yesterday. Since there was only 1 instance indicated by the reader, I figured that clearing and waiting would be more productive than a full blown panic.

So after another 8 starts and 30 miles the code has not returned. Good places to look though! When I get a few moments in a warm garage I'll chase the hoses and look for cracks. There is only 80K on this unit, but cracked hoses come with age. I may even check the gas cap. The tank is getting low, so that may come first

I do appreciate the help guys!

You should probably help ihscoutlover because he sounds like he has a whole mess of problems

Click to expand...

Perhaps, but even headers have to retain OEM emissions control devices (of whatever sort,) which still leaves emissions questions on road vehicles as OEM tech.