Jeep Commander Forum banner

1 - 13 of 13 Posts

·
Registered
Joined
·
143 Posts
Discussion Starter #1
Having just bought my Commander 3 months ago, I noticed the check engine light came on for the very first time yesterday, while driving. My next service due... such as an oil change is due in 488 miles and I was wondering if the computer is set to simply trigger the light to come on, when a service is soon due?

I wish I would have been staring at my dash when it came on...like if it comes on when it shows under 500 miles or something. Nothing seems to be acting up (although in 488 miles the odometer will hit 100,000 miles and sure my plugs are overdue), so I'm hoping its supposed to do that.

My wife's vehicle has a oil life percentage indicator that comes when an oil change is due soon... so I wondered if this was similar or if its supposed to kick on when its close to 100k for a specific service.
 

·
Registered
Joined
·
1,516 Posts
No. The check engine on my 4.7 06 XK does not indicate service due, I get a message saying oil change due or something close. You can do the key dance (turn your key on and off 3 times without starting the car and look for codes. If there are none and the light is out, I wouldn't worry about it. The light can be activated by some thing as simple as a loose gas cap.
 

·
Registered
Joined
·
3,037 Posts
What year, engine and 4WD system do you have?

The Check Engine Light (CEL) means there is a problem that was detected and needs to be corrected.

Creek already talked about the Engine Oil Change Required Message that will pop up in the EVIC on the Dash, it does NOT lite the CEL. Earlier Commanders, I believe it just counts down the miles between oil changes, later Commanders the PCM actually runs an algorithm to judge oil life based on the engine usage and conditions. There is no percentage indicator, you simply get the warning pop when its time to change the oil. You can reset it yourself easily if you change your own oil.

Already mentioned is the Key Dance to get the PCM to spit out stored fault codes, and likely the fault codes are the source of the CEL. The key dance does NOT spit out every code and especially very few or none of the codes for the other electronic systems. The manufacturers keep that proprietary to force you into the dealerships to pay for overpriced diagnostics and service, instead of making it easy for you to read the codes yourself.

If you're overdue for new plugs, you might be getting misfire codes, the PCM will detect before you can. Fresh plugs will regain some lost power and fuel economy and smoother idle and engine running as well, if the exiting plugs are burned away.
 

·
Registered
Joined
·
143 Posts
Discussion Starter #4 (Edited)
Thanks for the replies.

My Jeeps a 2007 with the Hemi. I'll see if I can pull up some codes up real quick and go from there.

Plug wise, it wont surprise me if they are shot. I was planning to do it myself sometime this month. I'm sure the plugs are long overdue. I've put about 3k on it since I picked it up and I was just getting ready to address plugs and fluid changes.
--------------------
Update: I just did the code check via the key dance and it shows code # P0302. I searched the threads and according to what I found, I'm getting a misfire in cylinder #2. Now that I think about it there was one point where it felt like a stumble for a few seconds on a long hill, just once yesterday but then it went away.

I was planning on swapping plugs this month since my 07 Hemi has less then 500 miles till hitting 100k on the odometer. I'm guessing the plugs are long overdue, so hopefully worn out plugs are the only cause.
 

·
Registered
Joined
·
3,037 Posts
If the misfires the PCM senses are bad enough, the PCM will shut down the fuel injector for that cylinder for a little while, to prevent raw fuel from be dumped into the catalytic converter and damaging it. That will make the slight misfire that is barely noticeable become very noticeable and it will feel like a stumble.

BUT, it can be nothing more than worn out plugs causing some misfires under certain conditions.

Yes, there is a thread for dropped valve seats, you'd notice more problems than this if that was the case. At this point, I would make the assumption worn out spark plugs are the root of your check engine light.
 

·
Registered
Joined
·
1,585 Posts
If the misfires the PCM senses are bad enough, the PCM will shut down the fuel injector for that cylinder for a little while, to prevent raw fuel from be dumped into the catalytic converter and damaging it. That will make the slight misfire that is barely noticeable become very noticeable and it will feel like a stumble.

BUT, it can be nothing more than worn out plugs causing some misfires under certain conditions.

Yes, there is a thread for dropped valve seats, you'd notice more problems than this if that was the case. At this point, I would make the assumption worn out spark plugs are the root of your check engine light.
Agreed :banana_hitit:
 

·
Registered
Joined
·
143 Posts
Discussion Starter #7
I'm also pretty confident its a matter of a plug(s) that are long past needing replacement. Interestingly enough, the engine lamp was on today this morning but then after fueling the gas tank and restarting the engine, the indicators no longer illuminated.

I wont be surprised if it comes back on. I'll just have to take note of what the engines feeling like, if it comes back on. I made an appointment at the dealership to replace the plugs next week.

I'd normally just do it myself and it kills me to spend the money, but I guess this time I'll have to eat the $305 plus tax. I'm wondering if I should/can just clear the code out before I take it into the dealership. I'm sure they would try to charge me for looking at and clearing the stored P0302 code.
 

·
Registered
Joined
·
47 Posts
If the check engine light turns on, surely there is a problem in the engine system. You will need to have it diagnose to know the error code.
 

·
Registered
Joined
·
143 Posts
Discussion Starter #9
I'm thinking it was just a matter of very badly worn spark plugs. I swapped my plugs out a few days ago and since then I haven't had any more problems, nor does the engine light come on any more. My plugs were eroded down about 40% and the positive post on each of them was rounded off. All the more reason to change them every 30k miles. Overall it was a pretty easy job, just time consuming.

I haven't done it yet...but still have to unhook the battery and clear out the old code.
 

·
Registered
Joined
·
3,037 Posts
If you do NOT have a check engine light, there is no reason to disconnect the battery and reset the PCM.

Likely the CEL was from misfires because of the eroded plugs. The codes will clear themselves eventually if they haven't already.
 

·
Registered
Joined
·
1,516 Posts
If the check engine light turns on, surely there is a problem in the engine system. You will need to have it diagnose to know the error code.
The check engine light can come on for something as simple as a loose gas filler cap. I have had it happen.
 

·
Registered
Joined
·
143 Posts
Discussion Starter #12
I didn't realize that codes will eventually clear themselves if they no longer trigger. I thought that once a code shows up, it stays stored in the computer till you physically remove it from the system.
 

·
Registered
Joined
·
3,037 Posts
The only thing the codes do is give a troubleshooter historical information to help diagnose problems. So even if the problem is solved, and the stored code didn't clear, as long as if the CEL is NOT lit, what difference does it make? If someone is going to look at the codes, you might want to let them know you had changed the spark plugs and they were way overdue and you were getting misfires because of it, but that is all solved now.

The PCM software has a bunch of rules for when it will set a code and when it will clear it. Some codes its sets immediately, some, like misfires, that can happen in a perfectly good engine, it has to occur often enough that it is NOT a random occurrence, then once the PCM does NOT see it reoccur in a long enough time, it will clear the code.

Many tests the PCM does, are simple checks to see if the circuit is complete, if the circuit is NOT complete or the shorted, then the equipment on the circuit must be broken or at least the PCM sees it broken, so it sets a code immediately. As soon as the PCM sees the circuit operating correctly again, the broken equipment or what cased the PCM to see it as broken must have been repaired and the PCM clears the code.

The PCM also runs self tests on the emission equipment on the vehicle, federally mandated OBDII, if it fails the self-test it will light a CEL and set a code, if it passes the self-test the next time, it will put out the CEL and clear the code.

The evaporative emissions self-test changes air pressure in the fuel system voids to test if the system is sealed and gas fumes can't escape. If the gas cap is loose, it will let air in/out and the test will fail, if you tighten it, it will then pass the test, thus the CEL goes out and the code is cleared.
 
1 - 13 of 13 Posts
Top