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I am new to this and in need of some advice.

I just purchased a 1999 Jeep Cherokee 4.0L, with 211,000 miles and have some electrical problems. I noticed that one of the two green wires on the back of the alternator had been cut and ran to the negative side of the battery. I fixed it and spliced the wire back together so its like it was from the factory. When you start the Jeep it runs really rough and stalls sometimes. The check engine light comes on as well as the check gauges light.

I tested the codes with my scan tool and it is throwing a P0123 TPS sensor high input code, and a P1698 No CCD Messages Received From The TCM code.

I bought a new battery and replaced the terminals. I did a complete tune up (Plugs, wires, cap, rotor, air filter, oil, etc.) Changed the TPS sensor and still the same thing. I'm not sure where to turn next and don't want to start throwing money at different things and hoping for the best. Any ideas on what I should try next? Also I tested my charging system and the new battery shows 0 volts. I'm testing the alternator tomorrow, but don't think that would cause all my problems.

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  • My gut reaction to what you've written is poor / bad earthing. It could be any number of things but my first port of call would be to clean up and grease all of the points where cables earth to the body, engine block, gearbox, etc etc...
    – Steve Matthews
    Commented May 19, 2016 at 8:45
  • the ground strap that goes from the valve cover to the firewall frequently breaks on these it may not explain the codes but it's worth a look. also check the harness where it wraps around the rear of the valve cover.
    – Ben
    Commented May 19, 2016 at 11:41
  • one of the wires you repaired is probably the field wire for the alternator check for 14v on that wire at the alternator plug.
    – Ben
    Commented May 19, 2016 at 14:29
  • Did you have these problems before you fixed the alt wiring?
    – Moab
    Commented May 19, 2016 at 15:15
  • Moab- yes the problems were the same before I started messing with the jeep.
    – Flexin
    Commented May 23, 2016 at 3:18

1 Answer 1

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For the TPS codes, it's probably a ground issue. Check for ground on the orange/dark blue wire.

If you have ground on that wire disconnect and examine the connector for damage or a pin that's come loose.

If you don't have ground you're going to have to examine the wiring harness especially around the rear of the valve cover. There is a splice in the harness that sends TPS signal to both the transmission computer and the engine computer.

As to the alternator. The wire that was cut, the only one makes sense would be the computer controlled ground wire (dark green/orange) on the alternator plug. Disconnect the plug and with the engine running there should be a pulsed ground signal or constant ground with the plug unplugged.

If there isn't inspect the wiring. If the wiring is OK replace the engine computer.

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  • Ben- thats good info and I will do more testing tomorrow and see what I find! Thank you everyone for the help.
    – Flexin
    Commented May 23, 2016 at 3:23

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