bryweb

NO BUS NO START INTERMITTENT

Vehicle - 2000 Cherokee w/96 motor, Stainless Dual Precat Header with all O2 Sensors hooked up, Viper Coil Swap - running a new Airtex Coil.

Did Engine swap about 3 years ago then the Jeep sat for 2.5 years.

Other issues; current e-fan squeaking when on, new generic fuel pump is a little loud. After fuel pump is pressured up I sometime hear it relay in the PDC click on and off quickly for a bit.

Recent Issues Fixed,

1. Due to Ethanol Sitting, Fuel Pump Replaced, Injectors Checked.
2. Had issue with coil cutting out at 3000 RPM's like Rev Limiter, Replaced JY with new Airtex and fixed it
3. Overheated one day when caliper hung up (new brakes, radiator, waterpump, thermostat, fan clutch)
4. Computer swapped for a 2001 Computer (had NO BUS, NO START with original 2000 Computer before it blew for Coil Issue)

NO START NO BUS - INTERMITTENT - Seems like engine heat or battery low are quicker to cause it to come up.

• This has been getting progressively worse, some days I would start it drive 10 miles, stop, and go to start it and it would not for an hour or so then started. Cranks, gets NO BUS on Odometer. NO GAUGES - I thought maybe it was heat related.
  
• I somewhat remember in the very beginning only once or twice getting no gauges no bus while driving and smacking the dash and it working again, but it has not happened in a long time while driving and this was after it sat a long time.
  
• Then the next day my daughter (her Jeep) would drive it stop and go all day and not have a problem.
  
• Then one day the battery got low and I noticed with a low battery it was NO BUS NO START all the time.

During the low battery time, and once when it was intermittent, I unplugged one at time and turning ignition off and back on each of the following and check NO BUS, and each time I still had it Crank Sensor, Cam Sensor, IAC, TPS, MAP, FAN, Coolant Temp, Speed Sensor, Trans Main Junction Connector, TCM, Coil, Fuel Pump, Antilocks (not in use), Drivers Door Plugs at kick panel (locks and windows), Dome Light and sensor up there, Hatch plugs (wipers, lock, etc) All connectors have been cleaned with CRC Automotive Electric Contact Cleaner!!! Dash Cluster connectors as well have been taken apart and cleaned.

All this time it never just died, it was always a starting problem.

Then a couple of weeks ago while I was on vacation my daughter grabbed her jeep from my house to move something and it died while driving down the road right after she left about 6 block away and would not start at all, even the next morning, so a friend dragged it home.

I went out a few days later and it would crank like before but still NO BUS NO START. So I was able to find another 01 PCM (PnP 1/2 day) and confirmed it did not have a SKIM, Installed it, it did not start at first, but while messing with things under the dash, column, and Cluster, I tried it once and it started and ran fine, then shut it off and it would not start again that day. Not sure if it was just fluke intermittent start or something moved.

I tried a different battery and crank sensor. this has happened with all 3 PCM, tried unplugging all the sensors to see if it got rid of NO BUS.

NOTE: Fuel Pump kicks on with key run, and so does E-Fan.

My OBDII Reader does power up when plugged in, but does not communicate with the PCM

I checked voltages at the DTC today with a new but cheap Sears Ohm Meter (My good one died and didn't want to use my free Harbor Freight ones)
Is the ohms off or correct, and what is my next step????? I am Lost and Frustrated.... and Googled Search my brains out for weeks.

I do have the 2000 Jeep XJ Factory Service Manual in PDF

All help appreciated

Bryan

The Jeep, my daughters trail rig.

CCKen

"Checking Resistance between 3 & 11 I got 61-62 ohm SHOULDN'T THIS BE AT 120 OHMS ?????"


It should be 60 Ohms. If it were 120 Ohms one of the termination resistors (PCM/Instrument Cluster) would be out of the circuit.


Remove the CPS connector and see if the Voltmeter and Fuel Quantity indicator come to life.


With the connector removed, measure the voltage at the body harness connector pin cavity with the Brown/Yellow tracer wire. You should see .015-.020 volts.


Probe the pin cavity with the Orange wire, you should see 5 volts +/- .5 volts.

bryweb

Will do, was hoping you would chime in, read many of your NO BUS replies, Thanks CCKen !!!

PS: I read 120 ohm was normal in one post, then 60 in another post.... my bad..... When re-read yours this morning as I printed all NO BUS threads and was highlighting what resistance and voltage checks to do this morning I read 60 ohms.

bryweb

Voltmeter only goes down to 20 volts.PS: I have NOT cleaned the two post grounds on block by CPS yet per instructions read, actually sliced my hand last week changing the bit in my die grinder to a brush, the wrench slipped and the palm of hand pounded it down on the work bench shoving/cutting the wrench into my hand (I should have got stitches - but butterfly it up and used a brace to keep wound together - ya I feel stupid ...LOL), hand is just becoming usable now but it has been raining last two days and jeep is in driveway at the moment. Will try to clean the grounds tomorrow.

Thanks

CCKen

As long as that hand is useable.....

bryweb

Ya, thankfully it was my left hand that got injured.... So I can still milk cows.... LOL

bryweb

Any suggestions regarding my voltage readings, or clean the engine ground posts first?

Thanks,

CCKen

The DLC voltage readings are a tad low but I think they are okay.


The resistance readings are jut a tad high but should be okay. There may be some resistance in the CCD Bus wires at the instrument cluster connection and/or at the PCM connection.


What do you mean by: "NOTE: Fuel Pump kicks on with key run, and so does E-Fan." The radiator electric fan should not kick on when turning the key to ON/RUN (engine not running).


The voltage readings at the CPS body harness connector looks okay. At least you don't have a bad clockspring (when taking the readings).


Grounds:


Yes, do the grounds at G101, and at G100, see pic.



.

.

bryweb

I know, its weird, but as soon as the key in run position the e-fan kicks on. Wish I remembered if it did it the times it starts, will try to pay more attention.

I cleaned connection G100 the day I messed up my hand, and will clean G101 today.

I will also take the cluster out and clean those connection again with CRC Electric Contact Cleaner.

I also saw some wire taps under the ignition switch, I will shoot a picture of those today, not sure what they were wired too (alarm maybe) as all custom wiring has been removed.

Thanks for the help

bryweb

I clean G101 today, took the bolts out, using the die grinder with a wire brush attachement and went at it on the bolts, nuts, block head, spade lugs, and sprayed CRC contact cleaner in the bolt holes and all the connection.

I cleaned the cluster connectors and tried it again, as well as tried a cluster I had out of a 99 XJ I had. Did notice that the Air Bag light was on and realized I never disconnected the Airbag Module to see if the NO BUS went away, so I will pull the console and try that tomorrow.

I also cleaned the PCM connectors again with CRC.

Still have NO BUS and NO START ISSUE.

PS: I unhooked the ground but left my Warn winch cables hooked up to separate battery terminals , when I was done I went to try to start it and it cranked with out me connecting the negative cable back to the battery..... WTF??? no negative cable hooked to battery and it cranked, must have grounded through the Warn battery cable.

Also I tried unplugging the coolant sensor, and jumping the pins in the coolant sensor plug with a paper clip, e-Fan just kept running as long as the key was in the run position.

Beyond unplugging the air bag module, do you have any suggestions for my next steps ??????

As always, THANKS !!!!!

CCKen

Looks like you have your hands full with trying to figure out how all those systems got buggered up.


The only thing I can recommend is to go through all the wiring and figure out what has been butchered then un-butcher it.

bryweb

OK - got it to start again today but still an issue.

Today I heard the ADC relay clicking constantly (I am hard of hearing), I know I swapped the ADC and FAN control relays before with each other, but today I pulled them both and replaced them with others I had.

Now the fan no longer runs all the time with the key forward and I no longer have a NO START NO BUS - IT STARTS

But I can hear the ADC relay buzzing for 2 seconds off 2 seconds buzz 2 seconds and continues on and off. ADC/PCM relay overloaded causing off/on buzz

So I started unhooking every sensor and plug I could, no help, pulled the cluster no help so then I pulled fuses (only ignition and ADC fuse stopped it in the PDC), so then I started pulling under the dash fuses and when I got to #25 the buzzing on/off heartbeat stopped.

#25 is the ABS (Not used anymore, completely unplugged, all fuses and relays pulled), Climate Control ???, Cooling Fan (Completely unplugged and all fuses and relays pulled), and Brake Switched (Unplugged under the Dash and at Drivers Rear Quarter all plugs unplugged)

If Fan is plugged in with the relay in, the fan will move just a bit every time the ADC buzzes.

Oh and if I unplug either of the two outer plugs on the PCM the buzz stops, but not the middle one.

I am guessing its a wiring issue, I believe I should be looking for a shorted wire but there is a lot of wire. Even with every plug I can find unplugged on the jeep and every relay unhooked it is still doing the buzz on and off with ADC relay plugged in.

And advice.

Thanks

Bryan

bryweb

Well let me start out by saying I feel like an idiot, BUT I FIGURED IT OUT.

It was a couple of problems and it costed me a couple of used PCM's ($35 ea)

Part of the issue was a bad Cooling Fan Relay, ASD Relay, and a different used PCM. Swapping out both relays instead of switching them fixed it to get my Jeep Running again along with the PCM, the second thing might have been an issue using a 2001 PCM in my 2000 (now that it is fixed I want to try a 2001 computer again just for grins). Oddly enough the whole fuse #25 issue mentioned above went away with different PCM - afterwards pulling the fuse had no effect.

BUT THE BIG THING was I finally found the Fuel Relay was giving me a weak ground where it should have been giving me 12 volts that I just figured out as a mechanic buddy came by and figured my Fuel Pump fuse was blown in the PDC (I swear I checked all the fuses at least once) - bad eyesight at old age is what I am blaming it on.

What was really strange is somehow the fuel pump was grabbing power via the PCM and RUNNING despite the blown fuse. This was causing the ASD relay to BUZZ and eventually blowing out PCM's.

So now the gauges work as soon as I turn the key, instead of only with the engine running, the ASD no long buzzes with the key forward but not running, and the Jeep starts much easier, before it liked a little gas when first started before it would idle.

I drove 4 hours from Tallahasseee to Tampa as Hurrican Mathew was hitting Florida Thursday and got (2) computers from the U-Pull-It in Tampa (closest place I could find a reasonable price one for my year ($40 ea), unfortunately one was bad (No Start), and the other one is not firing #1 injector (checked with a node light), so I need to return them both (to a closer LKQ U-Pull-It) location and now on a search for another computer.

Not real proud of screwing this up, but hopefully my mistake will help someone else learn - double check them fuses !!!! even if you do not think it is related (the whole time I heard the fuel pump kick on with a good pcm)

Thanks for everyone help !!!!

CCKen

Thanks for the follow up.


Yes, a lot of people say they "Checked" the fuses, only to find out the fuse was blown. The best thing to do when Checking fuses is to just replace them.