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Jon
Jon, ASE Certified Technician
Category: Jeep
Satisfied Customers: 310
Experience:  Master Chrysler/Jeep/Dodge Tech
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Ive changed the fuel filter, crank position sensor, cam

Customer Question

ive changed the fuel filter, crank position sensor, cam postion sensor on my 2000 jeep grand Cherokee 4.7. still showing po320 and po725 code failures....help!!!!
Submitted: 1 year ago.
Category: Jeep
Customer: replied 1 year ago.
it is difficult to start it wont idle properly the rpm goes up and down like it breathing. then it starts popping and stalling between 2500rpm and 3000rpm.
Customer: replied 1 year ago.
I tested the fuel pump right off the bat by disconnecting it at the manifold it is fully operational.
Customer: replied 1 year ago.
there is also a strange humming sound somewhere under the hood when I do actually get it started, it sounds like something electrical making the humming sound. I have not attempted to leave the driveway since the symptoms began out of nowhere, besides it will die if I try.
Expert:  Jon replied 1 year ago.

Hi, do you have a scan tool?

Customer: replied 1 year ago.
that is how I am getting the codes, po320 and po725
Expert:  Jon replied 1 year ago.

Ok, if you go into data display, is the crank sensor signal showing not present when you crank the engine?

Customer: replied 1 year ago.
I'll check it in the next hour
Expert:  Jon replied 1 year ago.

Ok, I'm guessing it will not be present considering the codes you have. If it isn't, check for 5 volts with a meter on the orange wire going to the crank sensor. Also check for 5 volts at the orange wire at the cam sensor. Let me know what you find.

Customer: replied 1 year ago.
I'm still working on it. Out of town till tomorrow. Will try tomorrow
Expert:  Jon replied 1 year ago.

Ok.

Customer: replied 1 year ago.
23 on orange wire from crank sensor
Expert:  Jon replied 1 year ago.

OK, that's a problem. I don't have a computer near me right now but unplug the crank sensor and recheck it. If it doesn't go up to 5 volts or very close, try unplugging all the other sensors 1 at a time and recheck. It could be a sensor shorting out that 5 volt supply.

Customer: replied 1 year ago.
All the other sensors?
Expert:  Jon replied 1 year ago.

Cam, crank, MAP, and TPS look like they're on that orange 5 volt supply. Try unplugging those and recheck for the 5 volts.

Customer: replied 1 year ago.
I will today and get back to you
Expert:  Jon replied 1 year ago.

Ok

Customer: replied 1 year ago.
Replaced map sensor appears to have fixed problem running fine.
Customer: replied 1 year ago.
Stalled once at stop light. Other than that, running good. May replace throttle position sensor as well, your thoughts?

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