I went to start my car today and it constantly cranks but doesn't start. I checked all fuses, swapped relays, checked maf, cam & crank sensors still no luck. After reading countless posts on the trusty Org I've come to the conclusion it's the ECU (or ECM). With the key in the On position the CEL & Airbag Light don't illuminate & the AT Check light constantly blinks for a few seconds. When cranking the security light is solid red. I tried to plug in my code reader but it will not communicate with ECU. I removed the ECU and visually inspected the circuit board and harness and I didn't see any visible problems. Anybody have any other advice or suggestions? I'm a little strapped in the cash department right now and don't want to spend any unnecessary money.
(I've had no problems prior to this car was last driven 2 days ago)
Thanks in advance.

 

The security light being solid red while you are trying to start the engine is the problem. The NATS security system is not recognizing the chip in your key and has immobilized by the car. Maybe getting the keys re-programmed will do it, maybe not. It depends on if the NATS module has failed.

Try this possible fix - cycle the key on for a second then off for 10 seconds. Do this until the security light goes out. If this doesn't work, you will have to have the key(s) reprogrammed.

 

Will NATS cause the CEL & Airbag Light to not illuminate with the key in the On position as well as not being able to read codes?

 

NATS will not prevent the codes from being read. The codes come out of the ECU, via the OBD connector. The NATS, like all other sections of the car, sends information to the ECU and the ECU decides what to do with it. NATS codes are in the P161x area.

Similiarly, the NATS will not prevent the CEL and Airbag lights from lighting up. At least I don't think so.

Possibly a fuse could have blown. Fuse # 59 under the hood by the battery supplies power to the NATS and the ECU and the ignition system (and other stuff). It is labeled ENG CONT 2 on the cover. Also check fuse # 58 that is next to it, ENG CONT 1.

 

bad key? i'd try another just to be sure.

 

Make sure you connect the ecm harness correctly, last time i removed mine i didn't do it right and had the same problem (The lever on the wire harness should be moved All the way to the opposite position
of lock before inserting on ecm then once inserted then you lock it in place....

 

Thought I would weigh in...just in case it's useful........

Have you by any chance used a different key in recent history other than one you were using on a regular basis? I had a nightmare problem with a Walmart key that was not a chipped key even thought Walmart said it would be. Check m other posts under my profile ID name (jontay) for more info on this.

I tend to agree with some of the other posts on your thread about the NATS system disabling your car.

 

Well I'm not sure about it being the ECU, but if it ends up being that let me know as I've got an ecu for my 02 that I picked up and would let go of cheap.

 

I only have one key. I've had the same key for 7 years and never had a problem. Even if it's the key the CEL & Air Bag should be lit with the key on (from what I've been told and read I could be wrong). I also forgot to add the AT Check light blinks about 15 times when I put it in the On position.

 

You are correct when you say the warning lights should light up when the ignition key is turned to the ON position. The light come on as a light bulb test. Have you checked the light bulbs for the CEL and air bags?

The blinking AT light indicates the TCM has the trans in Fail-Safe mode. Maybe you need to spend some time under the car inspecting wire harnesses for signs of critters chewing on them.

And how about some feedback on some of the things you have checked?

 

OP, did you ever figure anything out? I have an 03 that has the same symptoms, but my car will start, but then will go into this same fail safe mode you have described. Car will just crank and not start, my SES does not come one, and my AT Check light also flashes.

 

I'm going with this. I had a Jeep do that a few years ago