OKAY CHEROKEE FORUMS,

I live in Las Vegas and currently drive a 1998 jeep Cherokee sport 4.0 liter. everything is pretty stock as far as the motor goes (tranny flex-plate will need replacement soon). it has 240k+ thousand miles on it... but it still runs very strong. I have done most of the work under the hood myself. I would say on a 1-10 scale of how comfortable I am under the hood, I would be a 8 or 9. Electrical stuff worries me because of how hard to trace it can be. So now, right into the problem.

SIDE NOTE: THE CAR RUNS FINE. NEVER DIES OR SHOWS SIGNS OF HAVING ELECTRICAL PROBLEMS. THE CAR LIGHTS DO FLUX/DIM WHEN LISTENING TO LOUD MUSIC OR WITH THE WINDOWS ROLLING DOWN THOUGH.

Recently its been time to re-smog my jeep but the check engine light was on. FAILED TESTING. I took it to the parts store and they tested the battery and the alt. for me. both parts passed the hand held tests. I then double checked fuses, nothing blown. They ran the OBDii tester gave us three codes... P1682, P0622, P1698. All related to the voltage reading. Voltage not with 1 volt of the target. BLAH, BLAH, BALH... The meter on the dash reads vertical the entire time. Around 14 or 15 I think. (I can get a more detailed reading if needed.)

Now I know a bit about volts and stuff like that under the bonnet.

THREE MAIN THINGS>>>> BATTERY/FUSES, ALTERNATOR, or ECM.

So I took my battery to an Interstate state place to have it tested. the said it had a dry cell. So I bought a brand new battery. checked the terminals on the battery. The negative terminal is pretty beat up and I can provide pictures if needed but the connection looks fine. no corrosion on the terminals. I hoped the battery would fix the issue, 150 dollars later...
Check engine light back on after less than 10 miles.

So then I ordered a new ECM from B&R AUTO WRECKING. They tested the computer before shipping it to me. So I slapped the new ECM into the jeep myself. 3 screws and clips later the computer was installed and I started to drive cycle the truck. 108 dollars later...
No check engine light for 5 miles. then it kicked back on the day afterwards.

I am going to take the truck back into the local store to get the codes checked again, and to pick up a New Alternator for it. I'll be 150 dollars short after that new alternator.

Any ideas on what could be causing this issue?

ANY INFORMATION IS HELPFUL GUYS THANKS.

 

STOP THROWING PARTS AT IT

Codes are:
P0622 (G) Generator Field Not Switching Properly An open or shorted condition detected in the generator field control circuit.

P1682 Charging System Voltage Too Low Charging system output voltage low.

P1698 No CCD Messages Received From PCM Bus communication failure to PCM. A "Companion DTC" was set in both the ECM and PCM.



P1698 can be caused by a whole host of issues, usually a short or a poor ground.


My course of action would be:
1) remove the alternator and get it BENCH TESTED at the local auto parts store - this is free
2) clean up all the ground points - one is battery (-) to the fender, one is from near the oil dipstick to the battery (-), and the other is rear of the valve cover to the firewall. In each case disconnect the wire and inspect for any corrosion, and sand the connector terminal till it's nice and shiny. Do the same for the mounting point.
3) check the red wire from the alternator to the underhood distribution center - clean the terminals just like the grounds.


My feeling is the alternator has lost a diode or 2, which also explains the lights dimming under high load, and it needs to be replaced. But like I said, get it tested first before buying a replacement

 

A big thanks Dukie,

I WILL KEEP YOU UPDATED.

 

Just to add to dukie's post you also have 2 grounds on the coil and the mounting ares between the starter and the engine block is also a ground point. Also check the wires to the starter they can also cause some of the symptoms that you are having.