While crossing Pennsylvania last week in my 2000 TJ, I found my gas cap sitting on top of my tail light when I stopped to fill up. Over
100 miles at freeway speeds, the cap remained on the tail light; however, the check engine light did not illuminate.It should have?
Matt Osborn did pass the time by typing:
I did that with a mug of coffee. Only problem is I found it the second the jeep came to a stop. :) The mug was almost "spillproof".
Dunno. Usually you get a code thrown for extended idle with a cap off but it's not a 100% thing. Just something I've seen on jeeps that used an aftermarket locking cap that didn't seal.
There isn't a specific fault code either. It usually manifests as (fuel evaporator system) on a scantool. But IIRC it's a mix of TPS, O2, and MAP sensors since there isn't a specific sensor for the evap system.
Wow, lucky you! I think mine would have fallen off simply by idling my '85 CJ7.
I'd think your light would have come on, especially on a newer TJ ...but who knows. Since when has anything relating to gas/gas tanks/gas gauges ever read accurately on a Jeep? ;p
No.
The evap system monitor only runs after a cold start, and it has to fail two consecutive tests before the MIL is illuminated.
Hey bllsht, what sensors is that picking up? Far as I know it's a combination of TPS, O2, and possibly MAP. I can sort of see the MAP indicating a leak against TPS and IAC or some sort of fuel demand/O2 indicating excess fuel vapor for too long. Never had a clear answer as to the cause though, just know aftermarket caps are usually the cause. Any cloo?
Thanks. I was pretty reluctant to show up at the dealers complaining that my check engine light wasn't on.
LOL! Yeah, that'd probably be a first at your dealership.
To detect a leak, it only looks at one thing. The hall effect switch on the Leak Detection Pump, aka LDP.
Operating conditions must be right to run the test, and it will look at other sensors for that info, but they aren't used to detect leaks.
I must say, I've never had that complaint.
Had a similar - not the cap but the light not coming on...must have left the cap in Placerville when filling the spare cans. Didnt notice it (no lights on at all) until the next morning at Icehouse. You would think that no cap would do something, when on so many rigs a loose cap will turn the stupid check engine light on. Least you didnt have to pay for a new cap. =)
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