I have Grand Cherokee 1999 V8 4.7 220700 mphproblem: obd Give P 0505 1. Start good rbm at 750 as it heat rbm go up till 1500 2. When the heat come to middle oil pump fall down for a second and come back in middle quickly 3. Sudden die anywhere and all gauges down even when contact on 4. Give 3 signs: a. key original sign b. check gauges sign c. fuels pump sign. 5. After 15 min. These signs disappear all the gages go up normal the car normal start up. fix done: 1. Change iac motor 2. Crank Shaft sensor still the same Problem.

Fuel pump failure. Have someone open your gas cap an listen closely while you try to start the car. Your listening for a buzzing noises, if no noise pump has failed, very weak noise not enough pumping pressure to start the car. All 'n All "FUEL PUMP FAILURE"

You need to get it scanned with an obd 2 reader.

Try another inspection station. Contact Jeep for problems as this may occur more than you know.

Are any fault codes there? Sometimes O2 sensor can send this bad info to the ECU. Scanning OBD faults.

heater door servo's shot need to replace both

There are a lot of things to check:
- check ANY wiring connector at the engine incl. ECU
- check fuel pump pressure (45 to51 PSI, 2,95 to 3,2 at), there is a connector on the right fuel line, between injector 3 and 5.
- check the sensor on the crankshaft if installed the right way.
- check injectors for leaking
- check your vacuum system careful
- check your TPS
Check your OBD II-System, all functions Engine and Freeze Frame, Emission control etc.
You can check the OBD-System first. Connectors and Software for PC/Laptop are sold for $ 100 to $ 170 incl. OBD-connector and wiring. This is a one time investment that saves you lot of costs and time

What you brought is an tank and unit from 1995 JGC. from 1993 till 1995 they have the same fuel pump. 96'er Jeeps start with OBD - Systems and they have other fuel pumps. You can't change the plug ins, because you may have other fuel filter in your Granny. Check filter and fuel lines if they fit with the unit you brought. If not, you need another unit from a real 96'er Jeep

You need to check all the important fuses, the starter relay, the ignition switch, the neutral safety switch, wiring and starter itself, as well as block ground etc. Any shop you would take it to will need to test these items one by one till the problem is identified, using a volt meter or test light.Good parts and bad parts look the same 'till they are tested...though it would be nice if they turned purple or something when they fail, they don't.
If you want to fix it, start at the battery and work your way through the system 'till you find where voltage goes in but does not come out. That part is failed.
Shops don't guess...you shouldn't either.
good luck.
If you need help with testing a particular item, ask.

Change your Thermostat.

Ok it is obvious since the light is coming on you are getting power to the switch. It could be a heated seat relay. Im fairly sure jeeps use a relay after the switch that is where I would start. Check and see if the Heated seat relay, and fuse are good