DTC's P1686 P1687

SOURCE: 2000 jeep grand cherokee laredo showing code

Diagnostic Fault Code (DTC) P1686 has a generic description of "No SKIM Bus Nessage Received".
Diagnostic Fault Code (DTC) P1687 has a generic description of "No Instrument Cluster Bus Message"

P1688 is either not a valid code for your vehicle, or the manufacturer failed to provide specific information for it.
Basically, what is going on here is that you have a problem in your computer network communication bus. Or to put it more simply, the "phone line" is down. Your computers in your vehicle are having problems talking to each other.

"SKIM" stands for Sentury Key Imobilizer Module (AKA security module). The Instrument cluster and the SKIM are not communicating with the Powertrain Control Module (PCM) for sure, and possibly also not communicating with the Body Control Module (BCM). There may also be problems with other modules that share the same data lines.
This MUST be diagnosed with a scan tool that can access the entire computer network. You must find out which modules can communicate with the scanner and which ones cannot. This is necessary to determine the possible location of the fault.

SOURCE: 2001 Jeep Grand Cherokee stalled & will not start

check the battery to make it is fully charged and also put some dry gas in the gas tank

SOURCE: 2004 Jeep Grand Cherokee. Keeps stalling, engine

P0505 means the whole Idle Control system, not only the IAM. Check all related sensors (i.e. crankshaft sensor). Check with a voltmeter direct at the connector of the IAM if you get any signal. Remove the IAM from the TB, connect him, let someone switch your ignition key to ON. The IAM need to drive in/out for a short time to find the right position. Hold the IAM near a hard part, that they cant drive out completely! If IAM works fine, check the fuel pressure, check and clean your TB ( if not done yet). If that doesn't work, come back again please