2001 QC 4.7 AT 2WD ~270kmiles

Has been happening for years (5+)... upon start up the fuel gauge remains buried on Empty maybe 1 out of every 25 starts. There have been periods where it happened more frequently (multiple times in a row) and other times when it doesn't happen for a few months... There is absolutely no difference in how it starts and if the gauge registers on start up it works as long as the truck is on (meaning it never fails after starting if it worked when I started it). Similarly if it fails upon startup it never 'kicks in' at any point while the truck is running... I think it happens most frequently when the tank is 1/2 full or less... I'm one of those people that hates filling up... I've never run it out of gas but I almost always let it get to where the fuel light comes on before I fill up...

I've learned to work around this... but if it's something fairly easy to fix I'd like to... I presume it's an issue with the fuel level sensor which I understand is part of the fuel pump assembly... with the miles on my truck it's apparent the pump will eventually need to be changed... just thought there might be another [easy] fix so why not ask the experts!

 

given the symptoms produced...I actually highly doubt it is the fuel sender. Reason being: The sender is an active, mechanical device. It's constantly moving up and down and fuel sloshes in the tank (the PCM delays/buffers the cluster significantly to reduce slosh wiggle). It never goes to full empty when sitting, it always sits at fluid level.

Likewise, if this was a chassis electrical fault, it would alter states while running as connection made and unmade.

As a result, I'm going to say that this is either a PCM or cluster issue.

Next time you notice that the fuel gauge doesn't command at key-up, run the cluster through a self-test. On GM's, it's common for a gauge stepper motor to just go kaput. Dodge not so much...but check for the sake of checking.

If that verifies, then it's an issue in the PCM.

Is there any common times when it doesn't work? Wet, dry, cold, hot? Low battery voltage event?

 

Thanks... how do I 'run the cluster through a self-test'? Are you talking about doing the key test (on/off, on/off, on)? I just learned about that today reading through random posts here... I'm not aware of common times this happens... other than I think when tank is 1/2 or lower (and not 100% positive on this)... I will say it was worse a year or 3 ago and seems to happen less frequently in the past year or so... but still randomly occurs...

 

To test the cluster, hold the trip/reset button down, and turn the ignition on, the test will initiate, and you let go of the button. Will run all the gauges thru a full sweep, and all the lights will test.

 

Ok.. thanks... just so I'm following:

So the next time the fuel gauge doesn't register upon startup I should:
1. Turn truck off
2. Hold trip/reset button down and turn the ignition on (not starting the truck)

This will initiate the test cycle... I'll obviously pay special attention to the fuel gauge... if it fails to move or go through the full range that would point to a cluster problem... but if it passes I'm not sure it confirms proper cluster functionality since this is such an intermittent occurrence... but certainly worth testing... thanks!

 

May have to wait until it is a bit worse....

 

Yep... Agreed... But I'm learning some great stuff here in a very short time!

Just did the cluster test and the key code thing... All gauges/lights/sounds appear good and for the key test all I got was 'P done'.

Obviously this problem is a little annoying but doesn't cause a significant problem as I've lived with it literally for years and it hasn't gotten worse...

The only time this causes an issue is when my wife borrows my truck... She's my opposite... Never lets her car drop below 1/4 of a tank for fear of running out... And every time she needs to borrow my truck (you guessed it) it's either very low on gas or the gauge isn't working... Usually the former

Heck... I didn't even know I had a starting issue until she borrowed my truck about a month ago and she couldn't get it started in the home depot parking lot... After waiting a couple minutes it started and got her home... Of course my response was "never had that happen to me" and I drive it daily. The no start problem has now happened to me 3 times since... All 3 times I simply turned key off and tried again and it started right up... One of those times I did have to cycle key a 3rd time to get it to start. So I know it's going bad but not bad enough to debug yet...

Sorry to ramble... Point was only that although I've gotten used to the nuisances of my truck (intermittent fuel gauge, no AC on lowest fan speed, power windows only work from driver's door, etc) and although my wife only uses it once every couple months, if something is going to fail it will be when someone other than me is using it!

 

What's it do when you have a no start? Oddly enough..might be related.

 

Pretty much nothing.. engine doesn't turn over... no clicking... in fact it happens so infrequently that it always catches me by surprise and I find myself wondering if I turned the key far enough or maybe didn't hold it long enough... my immediate thought is 'user error' but I know it's not...

I realize it's possible the 2 issues could be related but the gauge problem has literally happened for years while the starting issue just started about a month ago...

 

Maybe a issue in ignition /electrical .