Another No Gauges, no power to coils, no power to injectors - JeepForum.com
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post #1 of 10 Old 06-11-2021, 10:56 AM Thread Starter
gold01wj
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Location: Farmington
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Another No Gauges, no power to coils, no power to injectors

Hey everyone, been a long long time since I’ve even logged in here but I’ve started having a hell of a time with my 00 4.7 wj limited. 215K miles, I’ve owned it for about 100K and 10 years. Last week my wife was driving, started running rough. She cut it off and tried to restart. Got the no gauges, no spark, no fuel injector power at the fuse, auxiliary electric cooling fan running really slow for no reason. It will keep the sentry light, airbag light and check engine light lit. No codes present when I checked at that time. The scanner does have communication to the pcm. I figured it’s probably the crank sensor. Hook my scan tool up and it reads engine cranking speed just fine… let it sit for a while, unhook the battery and it started back up and ran for a little bit but eventually if I cut it off It wouldnt restart.

Last week I was unable to replicate it running rough. Battery is charged 12.6 volts. Engine cranks just fine. Again when the gauges don’t work it still registers crank speed on the scan tool.

I left it sitting for about a week and a half and actually went and bought a Yukon Denali for my wife to replace the jeep(was in the plans anyway) today I go to start messing with the Jeep and it fires right up. I let it run for 5-10 minutes and it starts running rough but doesn’t stall. I can keep it running by applying throttle. Runs rough for maybe 15 seconds and clears out. Cut it off, it starts right back up. Let run another couple minutes and it starts running rough again, i keep it running as before and this time I get a p01494 leak detection pump code… I say wtf that makes no sense. After running a few more seconds it runs rough again and I shut it off rather than powering thru it. Try to restart… yep no gauges, no spark no injector power, slow fan etc same as when It wouldn’t start for my wife last week. Pulling the battery cables and letting it sit for a while is not always a guaranteed way of getting it to re-fire. After 1 key cycle the Po1494 code cleared automatically and I’m back to no codes at all. This is the only code it’s thrown the whole time. When it’s not running rough it runs and sounds completely normal. When it gets to running rough it will backfire thru the exhaust a little bit and miss pretty good. Crank speed does not seem erratic or anything like that when it’s running rough.

I’m an oil field mechanic for a living with a previous background in automotive. This one has me stumped. I’m kind of leaning toward the pcm going out. Anyone have any suggestions. I’d like to get this thing running and sold in the very near future.


2000 wj limited Selectdrive, 17 Moabs.
72 Chevy K20
57 Chevy 3100
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post #2 of 10 Old 06-11-2021, 11:13 AM Thread Starter
gold01wj
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Another quick bit of info. After the first post I went back and started it back up. It had sat for about 15 minutes battery cables still hooked up. When I left it I had no gauges, spark etc. got back in it and it fire up and ran rough for a second or two then it wouldn’t idle at all. Foot in it and it runs smooth and sounds normal but let off the gas and it dies. MIL momentarily lights PO443 another wtf. Code clears its self after key cycle. Engine starts back up still running good but no idle. This time I kept it running a few minutes in the same no idle situation and don’t get any MiL or codes. Nothing is consistent in what it is doing, which further leads me to suspect the pcm is gone.
Also this jeep has never thrown a MIL light the entire 10 years I’ve owned it so I find it really hard to believe that the with everything else going on, the two evap codes I’ve gotten are real. Especially since both cleared them selves. I have not cleared any codes from my scanner at all. The sentry light will also come on and stay on sometimes when everything is warmed up and engine running, never had that problem before either.

2000 wj limited Selectdrive, 17 Moabs.
72 Chevy K20
57 Chevy 3100
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post #3 of 10 Old 06-11-2021, 08:09 PM
Bigrigr
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Sounds like a bad PCM......Waterluvr.....

'00LMTD-4.7l,242hd,D30,D44A,3.73's,True-trac front,Spartan rear,4" short arm lift,JK'sW/32's
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post #4 of 10 Old 06-11-2021, 08:37 PM
HAZCAT
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Pull your cables from the battery and just leave them off for at least 30 minutes. While you are waiting check all the ground points on the fenders and firewall to make sure they look good. I always pull them and scuff them up and reattach. check the plug and harness at the alternator and make sure that looks good. You may want to test the alternator to make sure it is operating correctly.

Then on the drivers side under the hood at the firewall, look down and in the tranny bellhousing is the CPS. You may need to take it out and clean it and also use a light and see how the flex plate looks if an auto or the fly wheel if manual. That is a good thing to check with these symptoms.

Then you may need to check the return line for the unused fuel going back to the tank. Is it leaking? Is it pinched?

leaving the battery unhooked for 15+ minutes will reset the computer. It should fire up if it is getting power and the CPS is reinstalled (don't lose the paper spacer or make a new one if you do so it sits correctly) after a few minutes or reaching operating temp the choke should kick down and it idle. At this point is when you were seeing the problem which is when the computer takes over and uses the sensors to tell it how to adjust.

Don't assume it is the computer. Or frankly even the part the code tells you. Other things in the system can be bad but it causes something else to fail and throw a code. And if the computer reads too low of idle speed or current in the system it will shutdown.

'84 CJ7, 44, 14 bolt, twin stick 300, 109"whl base, 4 linked
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post #5 of 10 Old 06-12-2021, 03:38 AM
Delta0
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Quote:
Originally Posted by HAZCAT View Post
Pull your cables from the battery and just leave them off for at least 30 minutes. While you are waiting check all the ground points on the fenders and firewall to make sure they look good. I always pull them and scuff them up and reattach. check the plug and harness at the alternator and make sure that looks good. You may want to test the alternator to make sure it is operating correctly.

Then on the drivers side under the hood at the firewall, look down and in the tranny bellhousing is the CPS. You may need to take it out and clean it and also use a light and see how the flex plate looks if an auto or the fly wheel if manual. That is a good thing to check with these symptoms.

Then you may need to check the return line for the unused fuel going back to the tank. Is it leaking? Is it pinched?

leaving the battery unhooked for 15+ minutes will reset the computer. It should fire up if it is getting power and the CPS is reinstalled (don't lose the paper spacer or make a new one if you do so it sits correctly) after a few minutes or reaching operating temp the choke should kick down and it idle. At this point is when you were seeing the problem which is when the computer takes over and uses the sensors to tell it how to adjust.

Don't assume it is the computer. Or frankly even the part the code tells you. Other things in the system can be bad but it causes something else to fail and throw a code. And if the computer reads too low of idle speed or current in the system it will shutdown.
Don't assume it is the computer. Or frankly even the part the code tells you. Other things in the system can be bad but it causes something else to fail and throw a code. And if the computer reads too low of idle speed or current in the system it will shutdown.

I think that bit of advice is excellent Hazcat.
Well worth saying a many times as it takes.
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post #6 of 10 Old 06-12-2021, 09:22 AM Thread Starter
gold01wj
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Thanks for the suggestions; Pulling the battery cables doesn’t consistently help. I’ve been playing with that since the very beginning. I’m definitely not trusting any codes I get right now don’t worry. Alternator wiring was removed and inspected which changed nothing, tried that yesterday morning. The alternator is about 2 years and 15,000 miles old; It charges fine when it’s running, even when it wouldn’t idle yesterday it would show 14 volts when I had my foot on it keeping it running around 7-800 Rpms. It will start and run as long as the gauges and everything else aren’t dead. Last night after it sat for that afternoon and evening it fired right up and idled like normal again. I didn’t run it any more than a minute or so. I’ve been pulling the cables when not working on it because there’s so much goofy electrical stuff going on that I don’t want to come out to a dead battery. Fender and firewall grounds are clean and undamaged. I’m going to try and do the passenger engine block grounds today if I get time. Crank position sensor appears to be functioning correctly as far as I can tell, I’m going to ohm it soon as I get time to mess with it some more. If I end up getting a pcm for it, what do you guys thinks about this?
https://www.ebay.com/itm/13375082339....c100889.m5204

I’ve read the mess that can be rebuilt pcm’s, if I’m reading it right, these are verified good oem factory units that are just reflashed with my vin.

2000 wj limited Selectdrive, 17 Moabs.
72 Chevy K20
57 Chevy 3100
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post #7 of 10 Old 06-13-2021, 10:35 AM
three_jeeps
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Quote:
Originally Posted by gold01wj View Post
snip
If I end up getting a pcm for it, what do you guys thinks about this?
https://www.ebay.com/itm/13375082339....c100889.m5204

Ive read the mess that can be rebuilt pcms, if Im reading it right, these are verified good oem factory units that are just reflashed with my vin.
IMHO, all replacement PCM's are a crap shoot. they offer a 60 day warranty which offers some protection, if they will refund your purchase.
At $140 it is a low risk compared to most other options.

then again, you could go to a u pull it and get one yourself and try it just to see if it fixes the problem, then find a place it reflash it if that is the cure.
J
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post #8 of 10 Old 06-13-2021, 04:41 PM
Waterluvr
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Quote:
Originally Posted by Bigrigr View Post
Sounds like a bad PCM......Waterluvr.....
You forgot the @ ~just noticed this.

Bad pcm is very likely, grab one from a yard and drop it in what should happen is the dash will operate normally in conjunction with a crank/start/run for 2 seconds and auto shut down from the skim module.

You can mail it to me and I'll give it a proper flash for you so it's plug and play, be sure and match the part number sticker on the used pcm to what you have installed currently.

The last two digits in the part number do not have to match, they can be anything from (AE-AJ) send me a pm with your email so I can get in touch if you need help.
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post #9 of 10 Old 06-13-2021, 10:02 PM Thread Starter
gold01wj
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Quote:
Originally Posted by Waterluvr View Post
You forgot the @ ~just noticed this.

Bad pcm is very likely, grab one from a yard and drop it in what should happen is the dash will operate normally in conjunction with a crank/start/run for 2 seconds and auto shut down from the skim module.

You can mail it to me and I'll give it a proper flash for you so it's plug and play, be sure and match the part number sticker on the used pcm to what you have installed currently.

The last two digits in the part number do not have to match, they can be anything from (AE-AJ) send me a pm with your email so I can get in touch if you need help.
Sounds great, Im going to go to the local yard hopefully tomorrow or Tuesday and see what I can round up. Ive read a bunch of your threads over the last couple weeks and was hoping you would chime in. PM incoming.
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2000 wj limited Selectdrive, 17 Moabs.
72 Chevy K20
57 Chevy 3100
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post #10 of 10 Old 07-22-2021, 06:43 PM Thread Starter
gold01wj
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Join Date: Mar 2013
Location: Farmington
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Just a follow up for others who may hit this point in the future. After searching the three big yards we have here with no luck and seeing the used prices at the various online junkyard sites, I went ahead and bit the bullet for a reman unit from Fs1. I tried starting it immediately before swapping the pcm. No luck, same old no gauges, no start, etc. swapped the pcm and it fired right up. Drove it around for a little bit at operating temp, no issues. Starts up every time with no issues now. Up for sale it goes tomorrow. Thanks for the help here and thanks waterluvr for our email exchanges and your input. I really wanted to use your services but the cost of the uses pcms at the online sites with no flash, were real close to the price of the refurb units that come flashed and with free shipping. Not to mention if it only lasts 6 months or a year or whatever, it won’t be my problem frankly. (I will obviously tell the new buyer that the pcm has just been replaced. Thanks guys. I anticipate this could be one of my last posts on this site. It’s been a good run on here and I’ve enjoyed the time spent here over the years. Keep on Jeepin boys and girls!

2000 wj limited Selectdrive, 17 Moabs.
72 Chevy K20
57 Chevy 3100
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