This is part of the operation article found in the Alldata information website. If the light comes on then there is a problem somewhere in the system. Sometimes reprogramming of the system may be required to repair a software glitch. It could only be the key if the light flashes and goes out. If you have more than one car that have the chips in the keys and they are all on the same key ring then there is a slight chance that the other keys may be interfering with the signal and making the light flash. Try to use the key by itself and see if the problem goes away. If you have a Mobil speed pass, remove it from the key ring and see if the problem goes away.
The only real scan tool that can do this is found in the Jeep dealership.This tool is more sensitive and has more information than other scan tools found on the market. The Jeep dealership most likely has run across a problem like this and knows how to deal with the repair needed. It's a complicated system and needs an automotive professional to diagnosis the problem.
Here is the information below. I hope this helps you.
SENTRY KEY IMMOBILIZER SYSTEM INDICATOR LAMP:
The Sentry Key Immobilizer System (SKIS) indicator lamp gives an indication when the SKIS is faulty or when the vehicle has been immobilized due to the use of an invalid ignition key. The lamp is controlled by the Electro-Mechanical Instrument Cluster (EMIC) circuitry based upon messages received from the Sentry Key Immobilizer Module (SKIM) over the Programmable Communications Interface (PCI) data bus network. The SKIS indicator lamp uses a replaceable incandescent bulb and bulb holder on the EMIC electronic circuit board. If the SKIS indicator lamp comes on and stays on after the bulb test function, diagnosis of the SKIS and the PCI data bus should be performed with a DRB scan tool and the proper Diagnostic Procedures.
The SKIM sends messages to the EMIC over the PCI data bus to turn the lamp on for about three seconds when the ignition switch is turned to the On position as a bulb test. After completion of the bulb test, the SKIM sends PCI data bus messages to keep the lamp off for a duration of about one second. Then the SKIM sends messages to the instrument cluster circuitry to turn the lamp on or off based upon the results of the SKIS self-tests. If the SKIS indicator lamp comes on and stays on after the bulb test, it indicates that the SKIM has detected a system malfunction and/or that the SKIS has become inoperative.
If the SKIM detects an invalid key when the ignition switch is turned to the On position, it sends messages to the instrument cluster to flash the SKIS indicator lamp. The SKIM can also send messages to the instrument cluster to flash the lamp and to the Body Control Module (BCM) to generate a single audible chime tone. These functions serve as an indication to the customer that the SKIS has been placed in its "Customer Learn" programming mode.
The light staying on indicates a problem in the immobilizer system (other than a failure that would disable engine start-up). Best bet is getting it to a Jeep service department where they can pull up the immobilizer troubled codes with a specialized scanner, and properly diagnose the problem.
Here is the problem with my Jeep 2001 Grand Cherokee 4.0 and rough country suspension. Super bowl Sunday I drove it all around. Then monday morning went to start it and the key icon was on, it would start for 3 sec and shut off.
I disconnected battery for 20 minutes thinking it would reset.same keys with chip I've used for 5 yrs since I've owned the Jeep.(rebuilt motor at 90,000 miles ago) so I got the same result no start and skim key icon is lit on dash cluster. So I took it to dealer. They put it on there diagnostic machine and the mechanic said there was a bad ground under dash that was getting to much resistance. He got it to start after 3 hrs of messing with it. Now no dash clusters and they said they have no communication with computer on outside firewall nor to bcm or skim module. I was so mad they told me to take it with out paying for the services. Now all dash cluster worked before. I have all gauges not lights, temp,oil,coolant charging are gauges. I took a test light and have correct power going to the data connector. Now the dealer didnt show or tell me what wire was bad nor can I find the repair that he did. The rpm gauge doesn't work nor does the speedometer work along with all gauges and key icon is still on along with my MIL icon. HELP PLEASE.
Check your fuses to see if the mechanic blew any when he was trying to diagnosis the problem. Concentrate on fuse numbers 6, 9, 16.
Get back to me with your results.
all fuses under dash are good i didnt check the ones under the hood. should i check them also?
Yes, check all of the fuses under the hood and get back to me with your results when you can.
Will an ignition switch that is located on steering column be bad that would not reconize the key be the problem of no clusters working in the dash and not being able to get communication with the data port?
The key is recognized by the key cylinder and related immobilizer system and not the ignition switch. If the key is not recognized by the key cylinder then it will not allow the engine to start.
It is hard to diagnosis this problem with out me seeing what is going on. Who knows what the mechanic did to make the problem worse.
I am sending you some wire and plug schematics related to the instrument cluster and ignition switch. I hope they help.
The only thing you can do is to bring the vehicle to another dealer or reputable master certified mechanic and have him try to see what this mechanic messed up then they can diagnosis the original problem you had with the key. They have the specialized scan tool that will be able to help them diagnosis the problem.
The diagrams are listed below.
Is there a way to start that Jeep by bypassing the key security system? That is what the dealer did and we cant find the wire that was jumped to start the Jeep.
To bypass the system can cause more damage that you already have. This is a highly integrated system and should not be messed with if you don't know what you are doing.
Take it back to the mechanic at the dealer who did the job and demand it be put back into the condition that you bought it into the dealer so at least you can drive it.
They didn't charge you because they screwed up. Make them fix it.
Have a different mechanic work on the vehicle using their specialized scan tool to make the repairs. Without that scan tool it won't get fixed.