Service Engine light goes on and then goes off.

08-11-2010, 03:20 PM
Hey guys, me again. So I got the new fuel pump in my Jimmy and I also just got a tune up and a new distributor. My Service Engine / Check Engine light comes on still, but it goes off after a little bit. It will come on for say 20 mins to 1/2 hour and then go off, and I also realized if I open the hood of my car and let my car sit for a minute the light will go off if it is on. My car drives great since I've had the stuff done to it. IDK why the light is still on, I'm guessing a bad sensor or something minor like that? It doesnt come on too often really, usually a couple days it will go without it on, then i open the hood and let the car run for a min or it will go off by itself after a little bit and stay off for a few more days. It seems like it comes on when I make a turn really, really fast. But the car doesnt do anything out of the norm, the light just comes on. Any ideas?

08-11-2010, 06:17 PM
What year is your Jimmy and which engine does it have? Even during inactive times there is enough traffic on this forum that many of us won't remember those details from a prior thread.

If your Jimmy is 1996 or newer you should be able to get the codes read for free at a local chain auto parts store. Most offer the service at no charge. You'll want to get the exact code though rather than the parts guy's interpretation of the code. Do your research, don't just assume the part they tell the code says is bad is bad. The codes only indicate which system is identifying a problem, rarely will it specifically state a particular part is bad.


08-11-2010, 07:10 PM
It is a 2001 Jimmy and it has a V6.

Also, I realised when it happens. It's when I make a sharp turn really fast, it seems when my car switches gears during the turn it will pop up then. But it doesnt happen all the time. If I take my time on a turn it doesnt happen or if I turn at a reasonable speed. I did a couple sharpies today but it didnt happen. The light isnt on right now and it hasnt been for a few days.

08-11-2010, 08:00 PM
Like Shorod said, check for codes and go from there.
Post back what you find for additional help.

08-11-2010, 10:36 PM
Even if the light is not currently on there will be stored codes with your Jimmy's OBD-II system.


08-12-2010, 04:57 PM
Hey guys, got the codes read at AutoZone and I got:

I have a code for a Crank Position Sensor and the other one I got is for a misfire in Cylinder 2, which was P0302.

I'm taking my car in on Tuesday to get looked at, the guy told me that my coil in Cylinder 2 may be causing the misfire, I just got a tune up so I know its not the plugs or wires and I got my distributor replaced. The lady at my AutoRepair place said I have no coil in Cylinder 2 so that probably isnt the problem. Any ideas? Thankfully the sensor isnt expensive, the guy at AutoZone told me its $38 to fix the sensor.

08-12-2010, 10:11 PM
Did this check engine light just start after the new plugs and wires, or were the plugs and wires installed in an attempt to fix this? If the issue happened shortly after the plugs and wires, there's a good chance you either have a cracked plug in cylinder #2 or one end of the plug wire is not seated properly.

I'd focus on the cylinder misfire code first. If the Crankshaft Position Sensor (CKP) were faulty you'd probably have a no-start condition and/or a random misfire code of P0300.


08-13-2010, 12:38 AM
It came on originally when my fuel pump was going bad, which I got replaced a few weeks back. But for a while my car had been kind of stumbling/hesitating so I got a tune up in hopes of it fixing that. After I got my tune up the Service Engine ligt came on but it went off after a day or so. Since my tune up my car doesnt stumble/hesitate near as much as it used to. it does it once in a blue moon but its nothing like it used to. the Service Engine light has been off though for the past few days, usually it comes on for a little bit then goes off by itself.

I also noticed my car sometimes, more frequently since i got the tune-up, when I drive sometimes my RPM needle will go up and down by itself when I'm at a steady speed... it's kind of hard to explain so I'll give an example:

I'm driving at 30 MPH and my RPM needle starts to go up and down really quickly by itself, not a drastic change, but say 2-3 of the markers in between the RPM numbers. When it goes up and down you can feel the car gaining and losing speed as it normally when when the needle goes up or down. It only does it for like a second and a half or so. Could that be the misfiring cylinder?

08-13-2010, 07:02 AM
Yes, that could be due to the misfire. I would start by thoroughly checking the plugs and wires. I would imagine your 2001 has a coil pack and not a distributor. You could try swapping the #2 spark plug with, say, #3 and the #2 wire with one of similar length, although not the same cylinder you move the plug to. Then see if the misfire code follows the wire or the spark plug.


08-14-2010, 09:17 PM
On a lot of Jeeps with a bad CPS, the same cylinder misfires, rather than a random one.


08-17-2010, 09:12 AM
I have a distributor in my 2001, I had to get the changed recently. I don't have coils in my Cylinders though... I took it in to the shop today to see whats wrong

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