Intermittent Dead Gauges Ignition ON - JeepForum.com
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post #1 of 17 Old 09-14-2019, 10:29 PM Thread Starter
AjRagno
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Intermittent Dead Gauges Ignition ON

2005 LJ Auto/240,000 miles

Iíve been dealing with this for a while without resolution, so I think itís time to ask for help. Iíll also happily retest as necessary.

Symptoms

  • Turn ignition from OFF to ON
  • Gauges do not move
  • Fuel pump does not prime
  • SKIS light come on then goes off
  • Fuel light comes on then goes off
  • SKIS light comes back on solid
  • Fuel light comes back on solid
  • Turn ignition to START, engine starts, and all gauges come up

This is only an issue when turning the ignition from OFF to ON. I have never had any problems once I start the engine.


MIL

The MIL is supposed to illuminate solid with the ignition ON and then turn of when the engine is started. When the gauges are dead, the MIL does not initially illuminate but does come on when the ignition is turned to START and then immediately turns off when the ignition returns to RUN.

I have noticed that when the gauges are dead, if I just leave the ignition in the ON position, the MIL will come on after a while.

PCI Data Bus

When this occurs, the Data Link goes down, but I do not get a NO BUS message.

Initially I focused on the PCI network modules (Cluster, SKIM, Airbag module, Radio). I don't have a scanner capable of communicating with the the PCI modules, or a way to test the PCI Bus wire, but unplugging each module and cycling the ignition doesn't affect the issue.

Ignition

The actuator pins are intact. I have 12V+ at the ignition switch. Replacing the ignition switch and also cycling it with a screwdriver did not help. I have also tested with 3 programmed keys.

5 Volt Reference

I get 5.02V at TPS, MAP, CPS, CKP, and Speed Sensor. Iíve also unplugged all without affect.

Grounds

All grounds and ground connections have been cleaned and the wires/cables tested for resistance. This includes the battery terminals, harness and grounds, the engine to body/hood grounds and wires, the instrument cluster ground and ground wire.

Battery and Alternator

The battery is 1.5 years old and settles to 12.65V. The alternator charges at 14.2V. Coincidence or not, the alternator did begin to fail about 2 weeks after this issue started so the alternator is now relatively new.

Fuse Panel and PDC

All fuses in the fuse panel and PDC have been tested. Iíve also tested and swapped the ASD and Fuel Pump relays without affect.

I have power to fuses 9-14 behind the glove box. The 25A Ignition Switch fuse has battery voltage.

One thing I have found when the gauges are dead is that, without fail, if I remove the 20A ASD fuse, as soon as it's reinserted, the fuel pump primes and the gauges come up.

Is there anything else I could test or check without back-probing the connections at the PCM?

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post #2 of 17 Old 09-15-2019, 11:48 AM
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Great video showing exactly how it is behaving.

Everything seems odd but the one thing that stands out to me is pulling the ASD fuse (not sure how you happened upon that but might be very helpful). I assume that is fuse 9 in the PDC, right? If so, besides the ASD it also is the constant (B+) power to the PCM. By pulling it, then putting it back in, you are essentially resetting the PCM. I’m not sure what that means but here are a couple thing to try which might (or not) narrow it down.

I assume when you pull & replace the fuse you have the key on the whole time. If so, try it with the key off, then see if the gauges come on when the key is turned on. If it works with the key off that would be like disconnecting the battery then reconnecting it.

Also, try pulling the starter relay. Then turn the key on. If the gauges are down (as expected) turn the key to start & hold it there. Do the gauges respond? If not, release the key back to run position. Gauges?

Report findings & I may be able to advise further…
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post #3 of 17 Old 09-15-2019, 05:16 PM Thread Starter
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I appreciate the feedback.

Yes, this is fuse 9 in the PDC, and I am removing and reinserting the fuse with the ignition ON.

I happened upon this while testing for power at the terminals with ignition ON and noticed that when I reinserted the fuse, the cluster chimed, the fuel pump relay (I assume) clicked and I could hear the fuel prime. As I kept testing, doing this restored gauge function every time. I'm also certain that there was power at the terminals or I would have made a note of this in my records.

It wasn't until testing again last evening that I noticed after removing and reinserting the ASD fuse that the MIL flashed 10 times to indicate that the emissions control system is not ready for testing. I had performed TSB 25-001-07 a few years ago, and because this involved wiring for the ASD and Fuel Pump relays as well as the PSD fuse, I wondered if that may be the issue. As part of my troubleshooting, I did re-perform this TSB.

You are correct in that removing and reinserting this fuse with the ignition ON does have the effect of resetting the PCM, but it seems to only reset the ASD circuit. The trip odometer and radio are not resetting.

I will try removing and reinserting the ASD fuse with the ignition OFF. Because the issue is intermittent, it may take a while to confirm the results.

Very clever to suggest disabling the starter. I've tried to determine if something is happening in the START or RUN position to wake up the PCM, but I don't believe I've tried this previously.
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post #4 of 17 Old 09-15-2019, 07:10 PM
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OK, good so far.

I did not realize this is intermittent. I did notice it failed 2 times but not the 2nd of 3 tries but did not relate that to being intermittent but does make sense now. How often does it happen? After sitting for an extended period (days)? Mostly just first thing in the morning? Mostly when restarted after it is warmed up? I did notice in the video the temp gauge was up to about 160į or so.

Yes it is like resetting the PCM by disconnecting the battery but you are correct, its not exactly the same for the rest of the circuits.

I suspect this is PCM related so that is why I noted it that way.

I’m not saying bad PCM but related in some way.

Seeing the video I noticed that all of the normal cluster related functions appeared normal as far as timing out the chime & brake light, etc. The SKIM warning (line through the key) would be more like PCM, through the SKIM module so I am not too concerned about that at this point. Same with the CEL.

We are on the same page regarding the run vs. start waking up the PCM.

There are 2 possible issues I see in that area depending on results key to start without the starter relay. So post results as you can & will go from there.
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post #5 of 17 Old 09-15-2019, 07:55 PM Thread Starter
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Yes, this issue is intermittent, meaning it does not happen every time, but it does happen every day.

It first came up in early May. All I noticed at the time was the SKIS light so I went back inside and grabbed a spare key. When I put that key in the ignition, everything was normal so I thought it was resolved, but then it happened again a few days later with the spare.

As far as the conditions: I drive my Jeep every day, but because I work from home, I'll often take short trips. It has never happened the first of the day, but if I drive to the store about 2 miles away, it's almost always an issue when I get back in to start it for the drive home. It always seems to happen if I take a few short trips, but sometimes it's the 1st restart, other times it's the 2nd or 3rd.

I have considered it may be an issue with the battery, due to the short trips, but I've had the battery drained to as low as 12.3V while testing and it's still intermittent.

At one point, I did remove the PCM and clean the pins and connection terminals as well as the battery wiring harness. After that, I kept detailed notes (date, time, temp, location, mileage). I did this for about a week and this issue did not return during that time. About a month later, it started happening again so I check my notes and found that it was not an issue if I took longer trips (20 minutes+).

When I recorded this video, I believe I had been starting my Jeep in my garage and letting it run for a minute, then turning it off and trying again so I could record a video. That's why it's not at operating temp.

Update

It took a while to get the gauges to act up today. When they finally did, I removed the starter relay and, yes, the gauges do activate when the ignition is turned from ON to START.

With the ignition OFF, I also removed and reinserted the ASD fuse and then turned the ignition to ON. This was done 6 times today and each time, the gauges activated normally. All in today, I probably cycled the ignition from OFF to ON at least 50 times and the issue only occurred once. It will be a while before I can confirm the results of this action.
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post #6 of 17 Old 09-15-2019, 08:35 PM
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Just to be clear, with the relay pulled & with the key on the gauges were dead. Then you went from on to start & the gauges came up. Right?

From there it did not happen again?
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post #7 of 17 Old 09-15-2019, 08:57 PM Thread Starter
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It's a bit more detailed.

I cycled the ignition from OFF to ON quite a few times. I even started the engine a few times and then went for a short drive. During this process, the gauges came up normally every time. After returning to my garage, I again cycled the ignition from OFF to ON and again started it a few times. Finally, this issue occurred, once. When it did, I left the key in the ON position, then removed the starter relay, got back in and turned the ignition to START and the gauges immediately came up and remained normal after the ignition returned to ON.

After this, I left the relay out and again repeatedly cycled the ignition from OFF to ON. The issue did not come up again after repeated attempts over 5 minutes so I stopped trying and put the relay back in. I then went back to cycling the ignition and also started the engine a few times but the issue did not come up again.
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post #8 of 17 Old 09-15-2019, 09:36 PM
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OK, good. That make sense since there is nothing to actually cut the B+ power to the PCM between run & start which would duplicate the removing fuse 9 as you were doing. It also eliminates the starter engagement (somehow) causing the “reset”. So it apparently “resets” when 12v is supplied from the ignition switch to the PCM. That appears to happen through PCM (black) connector C-1, pin 30 which comes from a splice (S-172) in the pink/orange that runs from the ignition switch to the starter relay. I do not know the actual function of this feed but think it is unique to ’05 & ‘06s.

How & why this function causes what I will call a “soft” reset, I’m not sure but will have to think it through bit more & post tomorrow.
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post #9 of 17 Old 09-15-2019, 10:17 PM Thread Starter
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Thanks. This certainly does narrow things down.

I see the PK/OR wire also runs to the Airbag Control Module and the Passenger Airbag On-Off Switch. I don't have the On-Off switch in my TJ, but I have noticed that the airbag light does not always come on during the bulb check.
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post #10 of 17 Old 09-16-2019, 10:58 AM
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That pink/orange wire is on a different circuit which comes from fuse 9 in the fuse block (powered in run/start) so should not directly have an affect on the overall problem. It is interesting that the light check is intermittent. Always have to consider a possible connection to this but I don’t see it.

On a possible related note, you mentioned having power to fuses 9-14. Fuses 9-12 have run/start power, 13-14 have run/acc power. Were you considering something related to that?



More info needed. Is it true that once you get the no gauges happening, no amount of key off, key on will wake them up. Only by starting it will they come up (not counting pulling fuse 9)? I believe that is the case. If so here is my next thought…

Back to the reset with starter relay pulled. When you then turn it to start you also have the “run” circuit engaged (through fuse 12 in the fuse block). I wonder if that will work without having the key on power to the PCM.

When you do get the no gauges you could turn the key off & try tapping into that pink/orange wire & give it 12v power to see if that, in fact does reset the gauges without the key on. If you want to try is you could pull the starter relay & with the key off jump across the 30 & 87 relay socket terminals. That will engage the starter but also “back feed” power to C-1 pin 30. Then pull the jumper & turn the key on. Maybe a better way would be to pull fuse 12 so the PCM does not get key on power, leave the relay in & turn to start, then reinsert the fuse & try again.

I’m not sure what that will tell us except it is more data which might lead to something.


New thought.

I wonder if it is related to the distance driven as you indicated or maybe actually the time between shut down & restart. Saying maybe it is related to the temp of the PCM (& under hood temps). I have seen some (not many) problems apparently related to PCMs having issues mostly when above certain temps.
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post #11 of 17 Old 09-16-2019, 05:21 PM Thread Starter
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There was a tread about a similar issue a couple of months ago. In that case, it was an '06 LJ Auto that died while driving. Dead gauges (same as mine), but their issue also involved crack but no start. I was following the troubleshooting steps suggested there. Whether the gauges were working or not, I still had power to the fuses so I figured the problem was not there.

When the gauges stop working, if I am away from home, I will just go ahead and start the engine. I can't say with absolute certainty, but it seem that if the gauges are not working, repeated cycling from OFF to ON does not have an effect. I have found however, that if I take the key out and just wait a few minutes and try again, the gauges will activate.

I'm checking my notes and I do see that removing and reinserting fuse 12 activated the gauges. But unlike the ASD fuse, the result was not consistent. I will perform the steps you suggested as well.

Time between shut down and restart seems to be the most common factor. This made me wonder if there is a faulty capacitor in the voltage regulator circuit. I don't know however if the voltage regulator used to wake up the PCM is the same regulator that sets battery charge rate.

OPERATION - IGNITION CIRCUIT SENSE

The ignition circuit sense input tells the PCM the ignition switch has energized the ignition circuit. Battery voltage is also supplied to the PCM through the ignition switch when the ignition is in the RUN or START position. This is referred to as the ignition sense circuit and is used to wake up the PCM. Voltage on the ignition input can be as low as 6 volts and the PCM will still function. Voltage is supplied to this circuit to power the PCMís 8-volt regulator and to allow the PCM to perform fuel, ignition and emissions control functions.

I am assuming that the wake up that occurs in RUN should also occur in ON (the manual does not list ON as a position).

I bring up the voltage regulator because I did have an intermittent issue with P0622 (3-5 times over 2 years). When it became a consistent issue in late December, I tracked it down to the alternator field wire grounding out on the engine block. I spliced in new wire but the alternator always made a lot of noise even after this and then the code returned and the alternator began to die a couple of weeks after the current issue started. I have not had the code return and the new alternator seems to be working fine.

I know that voltage spikes kill PCMs, but short of replacing the PCM or adding an external voltage regulator, this is just a theory.
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post #12 of 17 Old 09-16-2019, 07:00 PM
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A quick clarification. I often use the term key “on” or ignition switch in the “on” position when the correct term is “run”. It seems less confusing to most people to say on (as in turn the key on, turn the key off). So if that is causing some confusion I thought it should be clarified. All of my references to key on would mean key to run position.



Yours is the first I have seen where with no gauge movement it will actually start.



It is logical to assume the ignition sense would be activated by the switching to run, not necessarily the start but since that would appear to happen when the fuse 12 power is involved it might not be so. It says run or start. Either way this is not waking up your gauges, yet it still starts. It almost seems like the PCM is not awake or at least the PCI bus in not active until it gets a start signal, apparently from the C-1 pin 30 input. Sometimes these things need to be sequenced properly & it acts like that is not happening. When you turn the key, the run sequence has to come before start so obviously the start needing to wake the gauges (PCI bus?) is not proper otherwise the gauges would never come up until the start.

Where does that leave us? The run circuit in the PCM is open & needs the start circuit to get things going? And only intermittently?? Going back to temperature related?

We think we are beginning to know what is happening. But why is the real question, and how to fix it.



A question about the P0622 code & finding a shorted generator field control wire. If that wire was shorting to ground it would cause the alternator to charge at max voltage. Did you have that and actually see or get voltage spiking? As you said, PCMs do not like spikes which applies to most electronics in general.

By any chance did the alternator “noise” coincide with high voltage readings?
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post #13 of 17 Old 09-16-2019, 08:02 PM Thread Starter
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We're on the same page with ON vs RUN. I like to make the distinction that RUN means the engine has been started whereas ON means that everything normally powered with the engine running functions (HVAC, turn signals, sensors, etc.), but the engine has not been started.

Since the Ignition Sense Circuit is activated in RUN and START, I've wondered if once the ignition position switch hits START, is the power then sent from the battery instead of a capacitor.

I have also considered that the Ignition Sense Circuit is sequenced, but I'm not sure how to test. If the PCM sends a signal to the fuel pump for example, and does not receive a return response, does this keep the Ignition Sense Circuit from activating.

Temp related, maybe. The issue did start in Spring, but it's occurred (or not) from temps in the mid-30s up to 110į inside my garage.

When I had P0622, I never noticed it was overcharging, but instead under charging. The first time it happened, I only noticed the Check Gauges light. Later on, I noticed when the Check Gauges light came on, the voltage dropped then immediately came up to normal. This was an intermittent issue. It wasn't until this past December that it became constant and I tracked down and fixed it (same day). These photos were taken the day it became a constant issue.

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post #14 of 17 Old 09-16-2019, 09:49 PM
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That is the problem once you get into the PMC, how to test. There is very little reliable info on the internals, especially the NGC PCM that is in the ’05 & ‘06s. My process in diagnostics is do not start with “the PCM is bad”. Test every known way until you are lead to the PCM as last component standing. Pretty hard to prove they are bad unless you can pin down a missing output. Understanding sometimes the missing link is internal & can’t be proven. These are even difficult to open compared to earlier ones so something like a leaking capacitor is difficult to find & other components hard to identify their function.

Looking further I see that the bad wire for your charging problem is not the ground side but the hot side. So spiking voltage would not be the issue. If that wire was grounded it could overload that circuit, I guess a driver, & possibly damage the PCM’s regulator but hard to see how that would relate to this issue, but possible, I suppose.

As for temp related I am referring to the PCM temp which is much more related to under hood temp than the ambient air temp. I think the under hood temp will be pretty close to the same depending on the time the engine is running & the engine load regardless of the outside temp. And the cool down will be somewhat faster on cool/cold days than hot.

As for the fuel pump control which is the same as ASD control the PCM switches the relay coil ground on or off based on the key on & crank sensor signals. It can throw various codes but do not think it has any other way to shut them down. As long as the engine is being cranked or is running the PCM should keep the relays energized.
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post #15 of 17 Old 09-16-2019, 11:04 PM Thread Starter
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The under hood temps are definitely up there. My Jeep operates at 210 (according to the gauge), and after shut down climbs just beyond the 210 dot. If I place my hand on the PCM after driving though, it's too hot to hold it there.

I made a couple of short trips today (4 starts) and didn't have any issues. I waited 5+ minutes between shut down and restart each time.
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