Electrical issues?

I have a unique issue. The truck won't start. The check engine light comes on when the truck isn't on, and then goes out when the key is on. But then the oil and battery light come on. It's turning over, but not firing. I drove 4 hours, stopped to get gas. Cranked the truck up and moved it to a parking spot, I added oil because it was a little low and now I'm having these issues. Any ideas?

 

You mean the CEL is on with the key off?
Or you mean it’s on when the engine is NOT cranking?

It should come on with key on, engine off.
And go out when cranking.

Let’s start with this, this question will help a lot.

 

It is on when the truck is completely off and no key is in the Ignition

 

What year and what engine?

 

99 3.4l 5spd sr5

 

I’m having a similar issue with my 02/2.7. 5speed 4x4
I’ve been chasing grounds and rigged wiring from the previous owner’s reality which they had the engine replaced and before that, a new frame. By the way of the short biography from the garage, both outsourced major projects were addressed with wanton abandon.
That’s the backstory and apparently, my present electrical issue is in league with an old high school football injury that’s coming back to haunt forty years later.
My oil light was the thing that I recognized similar to your issue.
My lighting wiring on the front passenger side was taking in water from the rigged repair job that I’d discover later.
I too have that problem with starting but my little dashboard light is the battery. I can start the truck now and drive it but, I don’t dare turn it off. I took a chance and drove it to work yesterday (40 minutes) avoiding using directionals, wipers, etc.
Arrived at work and sure enough, I turned off the truck and then tried to crank it back up and, nothing. After work my predictions were correct. Somehow, something resets somewhere.
I turned the key and she fired right up with no complaints. And again, I drove home with that battery light on the dash, taunting me. I’ve read about the igniter but haven’t found it yet by the air filter.

 

The truck wiring is all original. I have added a switch panel to run my accessories. The winch is wired to the battery, but I have a cutoff switch and it stays in the off position except when in use.

 

The battery is strong and is turning over freely.

 

the cel is on in the off and acc position and the temp gauge is all the way up. The cel turns off in the ign and start position and the temp Guage goes all the way down. I disconnected the battery and all the ecu plugs and then i turned the key to ign and my cel light came on with the others and it cranked and ran for a minute before shutting back off. Now it's doing the same things as before and my code reader isn't able to detect the ecu with the ign on the on position. I have disconnected both tempt sensors and that didn't change anything. The temp gauge needle is still spiked at the top when ign is off and at the bottom when ign is on.

 

Do you have a voltage meter or test light?
You are going to need one of those at a minimum.

The CEL is powered by the 10A Gauges fuse.
Which gets power from the Ignition switch.
I want to see if you have power on the 10A Gauges fuse with the key off.
And with it out of the ignition.

Or better yet, if it does, or doesn't have power in ALL positions.

 

My gut is telling me the eletcrial portion of your ignition switch is funky.

Here is a video https://www.youtube.com/watch?v=P4k0j6DlH-k

While I am not an advocate of the parts cannon this is one instance where a few dollars and a little time you can eliminate a whole lot of diag time.

 

Yup. My first thoughts a long time ago when this started happening was the ignition switch.
The evening that she screamed at me, I was in the middle of a huge snow squall. No power at all. No hazards, nada. Just the light on my jumper box staged on the rear bumper. Waiting for AAA to show up, while they were super backed up with other calls, I just kept retracing the whole history I’ve had. Then a cop showed up and I was psyched because I hardly had any lighting.
my hood was up and I was inside the truck. I decided to humor myself and try turning the key “one more time”. Nothing. Then I decided to go further and flip the key 180 degrees. Well, it started. I had lights and all the while the truck wasn’t on, the oil light was lit.
I asked the cop to close my hood and escort me to the village grocery store lot and I’d wait for AAA there. I never turned the truck off and it never stalled.
Thanks for the lead on the video. I’ll order one asap. Meanwhile, I’m hoping that I’ll be able to make do with the tactics I’ve been using so far.

 

I found the issue. I got it started once, so I figured i would start back under the truck and wiggle all the o2 sensors and any connections under the truck. I did this with the ign in the run position and kept checking of the cel came back on. I finally found that the ground for the diagnostic port to the engine was loose. I tighten it and it started right up. I probably would have found it much faster, but it was 12 degrees outside and I was in a gas station parking lot. I kept taking breaks to warm up. The truck has ran perfectly since I tighten the bolt. I appreciate all the help

 

Awesome you found it but I think that is a little strange that bolts just loosen themselves. I find the older the vehicle the harder it is to get a bolt out. Nevertheless you have 2 different metals involved you should clean the oxidation and age off of the connection.

 

I had just come from a 4 day wheeling trip in the mountains so I shook it loose somehow. It is weird that backed out.

 

I have also had most of my truck apart doing maintenance and updating. I live in the south so no rust and nothing is frozen on

 

I understand a couple 200 more miles south for me and I'm in Mexico. Cool cool glad you pin pointed problem troubleshooting. Goes to show little things cause big problems. Cheers

 

any time you have lights come on when there should not be, its usually a bad ground somewhere.

 

Glad your issue was resolved. Man made error sometimes can be enigmatic.