I have a 01 Grand Cherokee Laredo 4x4 with a 4.0. It has the coil pack not a distributor. Just finished a rebuild on the motor after busting 3 pistons and damaged the head. New pistons, rings, rebuilt head all the works. Has compression. Now here's the problem. No spark, no power to the injectors fuses and weak fuel pressure. Vehicle has new fuel pump and crank sensor. There is no power going into the coil pack. When key is in the "run" position the "no key" symbol is lit up in the gauges. This key was the one I got when I bought the jeep. I can only assume it's original it has the chip in it but the plastic gray coating is gone. It cranks over all day but never any power to the above mentioned. It did not come with the fob. Also has a new battery. All ground wires have been removed and cleaned as well as whatever they contact. Have poured enough money into this I'm at the end of my rope. Anybody have any suggestions? Btw it did run with the key I have I drove it many many miles.

 

Well now. The RFD chip in imbedded into that grey plastic coating. If that's gone, I'd assume the chip is also. Anyway, the SKIM is not seeing it. Ordinarily when that happens the engine should still start and run on the primed fuel in the rail, then die. The grey color tells me that is one of the original keys. One is grey and the other is brown. All aftermarket keys are black.

Both the ignition and injector circuits get their power from the ASD relay (Auto Shut Down) which the PCM turns on as soon as it gets a signal from the CPS. Same with the fuel pump relay. If the BCM (Body Control Module) doesn't read a valid key, it tells the PCM to shut it down.

I realize you just changed the CPS, but you should backprobe the connector to see if you get a pulse signal while cranking. On this item, it's best to use a Mopar part. Aftermarket ones suck! The new one should have had a paper wafer on the sensing end to position it the correct distance from the flexplate, then it gets torn off on startup. The magnet in a Mopar one is strong enough to pick up a screwdriver. Does neodymium mean anything to you? Aftermarket ones cheap out and don't use them.

After 98, jeeps use a digital data bus to send and read signals between all the sensors and modules. It gets very confusing trying to figure this out. Sensor signals are 5v, switching functions are 12v and are done by drivers in the PCM. Clean connections are important!

Check out the CPS and then come back. I have more to tell.

 

Cps checked good except no voltage going to it. Resistance was good. Re checked all ground connections and re cleaned. Checked all connections. Still the no key light is displayed. I forgot to mention the vehicle sat for about a month and in that time the battery totally drained. Ive read a few places that can trigger the anti theft shutdown to kick in? Heres a pic of the key that came with it.

 

Well, it looks like the chip may possibly still be in it. On the battery discharge, I couldn't tell you. My WJ sat for over 48 hours twice in the same week with the battery disconnected and it fired right up both times. I'm running out of guesses.

 

Does that have a key fob remote also?

 

It's suppose to. But didn't come with it and my dumb self never took the time and money to go get one done for it.

 

I asked because if you think the security immobilizer may have been tripped there is a way to reset it yourself. But... From what I am reading it requires the keyless entry remote to do this.