Lunchbox07

My 98' cherokee sport has been broke down for awhile. All my asd components and my gauges are not working. Check all fues and relays. I believe my options are a bad wiring harness or the computer. Does anyone know of something I should check before I go with one of those???

car5car

what is ASD?

Lunchbox07

Automatic shutdown.

CCKen

I take it you have the FSM wiring diagrams for your Jeep. And I take it it won't start.

Are you getting 12 volts at pin socket 86 of the ASD relay recepticle in the PDC when the key is in the RUN position. Same for the fuel pump relay. The ignition switch powers the ST-RUN bus from fuse 2 in the PDC. If there is no power from fuse 2 to the ignition switch in the RUN position there will be no power to the ASD or Fuel Pump relay control coils or to the PCM thru fuse 11 in the Junction Block.

The ST-RUN bus A-21 also powers the instrument cluster thru fuse 9 in the Junction Block.

If the ignition switch contacts for A-21 are bad you won't have ASD, Fuel Pump, or Instrument Cluster, let alone no PCM.

Lunchbox07

No I dont have a wiring diagram. But yes when I turn key to on position. The gauges (volt meter, fuel) dont come on. The fuel pump dont kick on but we know its good. Mechcanic said my asd (automatic shutdown) components werent working as well. All it does it crank but wont fire. My last resort is the pcm/ecm or bad wiring. I believe.

car5car

good luck

CCKen

How do you know the fuel pump isn't working? Some fuel pumps are very quiet. The pump will initially turn on for 1 to 2 seconds to prime the fuel rail just before starting when you turn the key to RUN or START, then when the engine starts it will run continuously. Crawl under the Jeep just below the fuel tank and have someone turn the ignition key to RUN and listen for the pump (you'll need a quiet environment to hear it sometimes). If you can hear the pump run for a second or two you're okay; if not, you do have a problem with the electrical circuit(s).

As far as dead instruments and the engine not starting, the Crankshaft Position Sensor (CPS) has been known to create these problems. A quick check is to disconnect the engine harness connector from the CPS pigtail connector, turn the key to RUN and see if the gauges come to life. If they do it can be assumed the CPS is bad and should be changed. If the gauges do not come back to life further trouble shooting is requird.

Try these two things and let us know what you find.

Lunchbox07

Ok. I will try this. But where is the CPS? I dont know much about it.

car5car

bellhousing driver side(transmission)

Lunchbox07

Ok thanks.

hbracing13

Make sure that your battery is fully charged too. Crank sensor cam sensor will to it too. I know you can do a cluster self check, I don't know if you can do it or not, but you hold down the trip and reset button and turn the key to run, and in about 5 sec or so code should pop up, where your od reads.
Also the cluster the connector they get a hairline crack on the solder joints and touch them up, if that the case.
(I'm on the app so don't know what year you have)

CCKen

Location of CPS connector:

Lunchbox07

Ok. I unplugged the CPS at the engine harness. And turned the key to the run position and everything came on. So hopefuly changing the cps will fix my issue.

CCKen

Outstanding.

Did you check out the fuel pump yet?

Edit: Don't cheap out on the replacement CPS. Get a quality one from ther Dealer, or at least NAPA.

Try the replacement CPS before removing the old one. Plug it in and see if the instrument cluster works.

Lunchbox07

The fuel pump worked when I unplugged it and tried it. I found on another forum that said. That the pcm sends power somehwere at first turn of key and it goes thru the cps. It said if the cps does not send a signal back to the pcm within a couple seconds the pcm cuts the ground off to the asd and fuel pump relays. So therefore no power to anything. Hopefully will have fixed tomorrow.