• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Help. Stranded and Late for Work.

98NWCherokee

NAXJA Forum User
Location
Portland, OR
1998 Cherokee XJ
4.0
AW4
2WD with 8.25 rear axle
165k

Yesterday I drove the Jeep all around town with no problems. On my last errand, when I got back into the Jeep I noticed the power door locked cycled once on their own. I didn't think much of this and continued home. Parked in the garage where she's sat until today.

I go to start and nothing. No click, nothing but the emergency brake light. I notice the dome light is dimmed so I assume dead battery. I hook up a jump box and the moment I give the system power the door locks start cycling like crazy non-stop. I yank the fuse for the PDL's and now that's stopped at least. I still have a no start condition. I get no MIL and the only gauge that moves is the oil pressure gauge. I also hear a LOUD rapid clicking from under hood. I suppose it could be the starter solenoid, but it sounds SO fast. Is the battery just that dead? I find it hard to believe I've blow my CPS and develop an electrical gremlin in one night.

Help! Thank you.
 
I say have your battery tested and check connections and go from there. Doe's it fire up with the jumper pack on?
 
I was able to get a ride to work.....getting home is another story.

I'm thinking that the power door lock wire in the door loom chaffed and caused a short to power. Without my knowing, the door locks were probably cycling all night long until the battery died.

What I don't understand though, is why it wouldn't jump. I pulled the fuse and put a 50 amp jump box on it.
 
worth mentioning......if the battery is in really, really bad shape, jump box won't be enough. this happened to me when my red top optima shorted internally/lostacellorsomething a couple years ago. swap the battery out for a known good one and clean the terminals.
 
Thank you everyone for your suggestions. I'm still at work and will be until 2300 hours. When I get home I'm going to remove the battery from the Jeep, connect it to my 10 A charger for at least 3 hours and then problably drop it down to 2 A while I'm asleep. I'll clean the connections and check my engine grounds. The battery is about 5 years old and it's an Autolite battery.
 
Update...

As soon as I got home at 11:15 I threw the charger on it...10 amps. I went down to check it after about 90 minutes of charging. I did not try to start it, but I did notice the dome light was very dim and when I went KOEO I again had no gauge bump except the oil pressure gauge. I would think after 90 minutes I would start to see some power going back into the battery.

So, tomorrow I'm thinking I'll throw the battery from my other car in and see what happens. Then I'll take the old one to have it load tested.

I really hope it's just the battery. The door lock chaffed wire issue can be dealt with later. I need this Jeep to run for the next 4 weeks while I finish school.

Thanks and keep any suggestions coming. I'm relying on a 26 year old car to get me to work at the moment.
 
Got the battery load tested today.

It's rating was 650 CCA
It's output was 5 CCA

Needless to say this is part of the problem. A replacement 850/700 CCA battery is in my trunk to be installed tonight.
 
Update:

I put in the new battery and now I have a crank with no start condition. The fuel and volt gauge do not move at all and I get no MIL at all. I don't get NO BUS and the odometer reading does appear. I disconnected the CPS connector and checked the gauges.....nothing with KOEO. I swapped out the ASD and fuel pump relay and made no difference.

I'm very confused as to how this can manifest itself along with the crazy power door locks all at once. Since the CPS connector disconnect test did not bring my gauges back does that mean the problem likely lies elsewhere? Could I have a short in one of the door switches dragging down the whole system? The fuse is still out for the power door locks. Could a failing ignition switch cause this?

Please help. Thank you.
 
Last edited:
Is the PCM supposed to get warm/hot? With the key on the front of the PCM (towards the grill) gets hot in about a minute.

Can the CPS still be bad if the gauges don't come back when disconnected?

Really hoping i can get some direction here guys.
 
Last edited:
Hate to ask but have you checked all the fuses in the Power Distribution Center and also in the Junction Block?
Don't know about the PCM getting warm... I will check mine (01XJ) after I go for a ride to the store.
Your instrument cluster should do a lamp test for about 3 seconds when you first turn the key to on.
 
Thanks for the reply McQue. My test light and DVOM is at school along with all my tools. I know a visual inspection of the fuses is not conclusive, but they look alright and don't appear burnt.

I can do the bi-directional gauge sweep from the driver's seat and all the gauges work when going through the self-test. After that, I get just the odometer reading and the parking brake light.....no gauges no lamp test when key on.

I'm wondering if I had one problem and then caused another. When I hooked up my schummaker battery charger up to the old battery I initially put it on the 50 Amp engine start function. As soon as I did this I heard was sounding like a loud clicking from the starter/PDC area. It wouldn't do it constantly and I couldn't quite hone in on it's location. Could this have shorted something out.....like the CPS?? My old battery was only pushing 5 CCA so maybe it couldn't hold enough of a charge to energize the relay coil??? I'm reaching here I know....

I'm having it towed to my school/shop tomorrow morning so I can do some proper testing. At least I know I'm starting with a good battery. My connections appear clean.
 
Update:

Got the Jeep into the shop and started testing.

I have no spark and no fuel, although the fuel rail is pressurized.

Fuses are good and power at ASD and fuel pump relay checked with test light (ruling out ignition switch).

I have NO 5 volt reference on the shared signal line.

I've pulled the IAC, MAP, TPS, VSS, EVAP purge solenoid, low pressure AC cut switch, cam position sensor, crank position sensor and NO 5 volts.....just trace voltage.

I have battery voltage and a good ground to the PCM. The PCM still gets warm to the touch near connector A anytime the battery is connected.

So, it would seem to me that I have a bad PCM here. I don't want to replace it however just to have it blow again because I have a short somewhere. Should I do additional testing on all the sensors to make sure I don't have a short somewhere that could render a 2nd PCM a paperweight.

I put the door lock fuse back in and they cycled once and stopped. I hit the switch and they all worked. I removed the fuse again. So, my theory as it sits goes 2 ways.....

1. I had a short to power in the door lock circuit which drug down the battery. When I jumped it, either do to age just dumb luck the PCM fried.

2. The PCM shorted internally initially, dragging the battery down confusing the door lock module with questionable voltage.

Thoughts?
 
Last edited:
Maybe you should check the heath of your CCD Data Bus.

Refer to the schematic below.

You'll need a high impedance digital VOM.

Study the schematic.

Turn your ignition switch to RUN (ON) engine not started.

Using your voltmeter, touch DLC pin cavity 3 (+ probe) and pin cavity 4 and or 5 (- Probe), you should see around 2.49 volts (perfect system).

Touch DLC pin cavity 11 (+) and 4 or 5 (-), you should see 2.51 volts, again perfect system.

You should never see as low as 1.8 volts or as high as 2.8 volts on either CCD Bus circuit.

You may see the CCD Bus (+) and (-) circuits pretty close to each other but if you have a good voltmeter you may be able to dig down to three decimal places and see a .01 differential; between (+) and (-).

Check this out and get back with your results so we can see what you are dealing with.

Cheers






DLC.jpg
 
Thank you Sidewinder. I will check that for sure....but let me ask a follow-up question. Can I assume the CCD bus is down because I could not communicate with a scan tool? I think I forgot to put that in my list of tests, but I did hook up a MODIS to the DLC and got no connectivity. I'll still do the test as you suggest.

I see the RKE module is involved here as I do have the overhead console and that does relate slightly to my door lock issue. I was struggling to find a connection between the door locks and the crank but won't start problem........could that be it? Could a shorted RKE module pull down the shared 5v reference?
 
The PCM generates the 5 volt supply for the sensors... My PCM does not get hot like you are describing. I would check resistance measurements on the 5 volt line to signal ground to see if you can find a short circuit. IF no short circuit and still no 5 volt output, I would agree that your PCM must be fried.
 
So check resistance for all the sensors on the shared 5 volt line? Can you think of any that I missed? Looking at my Mitchel diagram it doesn't look like the O2 circuit shares the 5v line but its hard to tell.

Would they all be OL, or should there be resistance specs for each sensor?

I definitely want to rule out a short in case I drop a new/used PCM in it.

Any ides on PCM costs? A quick search online looks like they're under $200....what about flashing?
 
Last edited:
Check resistance from the 5 volt line to ground. It should not read a low resistance. I would check it by unplugging the Map sensor, and then check resistance from the harness connector 5 volt pin, to ground. You have not missed any 5 volt sensors as far as I know. You want to match the PCM to your year vehicle and options, like type of transmission, type of key entry, Air conditioning, etc. Dealers can flash the VIN # and mileage for a fee. If you search hard enough you will find places you can send your PCM and they will send you back a refurbished one ready to go once you provide them with all the info they need to flash it properly. But first you have to prove to yourself the PCM is bad. Long shot would be to open the 5 volt circuit coming out of the PCM and connect a temporary 5 volt feed to the harness side only to see how your symptons change. Maybe you can use and old personal computer power supply if you haver the skills for this type of test. It may or may not help you more cleary decide the PCM is dead. At this point you dont have much to lose.
 
Thank you Sidewinder. I will check that for sure....but let me ask a follow-up question. Can I assume the CCD bus is down because I could not communicate with a scan tool? I think I forgot to put that in my list of tests, but I did hook up a MODIS to the DLC and got no connectivity. I'll still do the test as you suggest.

I see the RKE module is involved here as I do have the overhead console and that does relate slightly to my door lock issue. I was struggling to find a connection between the door locks and the crank but won't start problem........could that be it? Could a shorted RKE module pull down the shared 5v reference?

Any module in that schematic can corrupt the CCD Bus. If it is found that the CCD (+) and or (-) circuits are not within spec, the process is to , in turn, disconnect the modules until the voltge(s) return to spec. The one that does return the voltage is the bad guy.

The Instrument Cluster is the last one to be disconneced because it is the Bias and Termination Resistor module.

Do the voltage test and see what you get.
 
Back
Top