2004 Suburban PCM/Fuel Level Problem

[TylerHagerdorn]

I've never been able to get my fuel gauge needles on my 2006 all the way to the full mark. I just thought that's how they were. But now that remember, I did the cluster LED and maybe I installed the needle a little off. Lately I can't recall the last time I tried filling up at 37 gallons anyways.

I haven't tried on the 04.

You are correct on the fuel gauge needle being controlled by the Class 2 data, I just saw that. If the issue was only that it didn't go to the full line, I would say just pop the needle on the cluster and re-stab it on the right position.

My cluster is from ISS. They are the ones who started rebuilding GM clusters many years ago. GM was sending them to the dump when iss started having them send them to them to rebuild...so I doubt they'd let it go with the needle in the wrong spot... especially two in a row because the first one we thought was defective because the DIC screen was dim. And is still dim and can hardly see it in the sunlight but it was bright on their test bench and they put a brand new screen in it too. So I'm sure they tested it multiple times before being shipped out.

Sounds like it's the PCM needing flashed and updated.

 

[Rocket Man]

If the gauge has its full range of motion, you could remove and then install the needle to correctly display the fuel level. Simplest solution, might not be the correct way but if it works it works, and who would know ?

 

[Fomoodie]

Hey Y'all.

My 04 Suburban is driving me nuts. I'm not sure where to go from here. Heres what's been done.

New rebuilt cluster, new Delphi fuel pump, used PCM matching numbers and from a truck with matching RPO codes.

I had a junkyard PCM I installed on Saturday, then we installed a new Delphi pump. Then went and filled the truck up. Gauge was reading dead empty. We hadn't changed wiring, but upon research the PCM was from a VIN T GAS truck, which the pump connector is different so the fuel level wires must have been opposite. Because as we were driving, the fuel level would go like it was using fuel normally.

I installed my original PCM again and it wouldn't read past half. When I know my fuel level was 3/4 tank. I had suspicion that the PCM might have been bad on that circuit. So I hunted down a PCM from a VIN Z Flex truck with matching rpo codes as mine.

Installed it yesterday, did the security relearn and it runs, but the gauge will still not read over half. I'm just completely lost right now. I have 19 plus gallons in my 31 gallon tank, and should be 3/4 tank or close to it. It's driving me nuts because I know it has to be something so simple.

Where do I go from here? Nothing was obstructing the level in the tank. I know according to my diagrams that the fuel level sensor goes from the pump to C152, then to the PCM. PCM connectors are good. I have not gone and put more fuel in it to see if it'll move up past half. But it's just strange to me that it refuses to move any higher than half.

Sorry if I've discussed this before. I know my other threads were a bit different. We have to be close to finding our what the true issue is.

If you’re getting the proper voltage, I would suspect a lazy cluster motor. Ever change them? It’s very common on those clusters to crap out. Motors are cheap, requires some soldering skills. Plenty of videos online, plenty of guys test and repair them..

 

[TylerHagerdorn]

If you’re getting the proper voltage, I would suspect a lazy cluster motor. Ever change them? It’s very common on those clusters to crap out. Motors are cheap, requires some soldering skills. Plenty of videos online, plenty of guys test and repair them..

Did you not read the whole thread? The cluster is NEW. Purchased from ISS which is one of the best, they are the ones who started rebuilding them for GM back in the day. They have a contract with GM. It's not the cluster I can promise you that. As someone had previously mentioned here, it appears to be a PCM update issue...so I'm waiting for my vcxnano to arrive and I will do the updates myself and then I will update this post with my findings. Never thought that GM would have PCM updates for these trucks in 2023, but it's a crazy world.

 

[Rocket Man]

Did you not read the whole thread? The cluster is NEW. Purchased from ISS which is one of the best, they are the ones who started rebuilding them for GM back in the day. They have a contract with GM. It's not the cluster I can promise you that. As someone had previously mentioned here, it appears to be a PCM update issue...so I'm waiting for my vcxnano to arrive and I will do the updates myself and then I will update this post with my findings. Never thought that GM would have PCM updates for these trucks in 2023, but it's a crazy world.

Well I mean the updates were made available like 15 years ago so it’s not like GM is still updating this stuff- now that WOULD be crazy. They were done with this platform a long time ago.

 

[Fless]

Well I mean the updates were made available like 15 years ago so it’s not like GM is still updating this stuff- now that WOULD be crazy. They were done with this platform a long time ago.

So true, none of the calibrations for these has been updated in years. When I updated the calibrations in my '04 Hoe there was not an update for the cluster; it was either the original calibration or already updated.

At any rate, ISS would surely be applying any available calibration updates to the clusters they repair. A Tech 2 can read the existing calibrations for all installed modules.

 

[mattbta]

It’s the fuel calibration in the PCM that is updated. I did a compare and can see they tweaked the table a bit for the fuel level. I want to say the counts from the fuel sensor were changed to update the voltage sent to cluster, but I’m fishing on the Gulf and memory isn’t the greatest.

 

[Fless]

So it sounds like the next critical step is to verify, and update if necessary, the PCM with the latest calibration. "Latest" being probably at least 15 years old, but newer than what is in it now.

 

[xpage]

Curious to an update on this. I have an 04 with similar issues. Checked the fuel sender and voltages seemed fine. Burb wasn't used in a few years and it's a project vehicle. Thought it was the cluster motors and some others were giving wonky values. After replacement, same empty fuel and low fuel light is constantly on, even with a full tank. Wondering if I should start wire tracing or redrop the now heavy tank and replace the sender or fuel pump.

 

[Fless]

Curious to an update on this. I have an 04 with similar issues. Checked the fuel sender and voltages seemed fine. Burb wasn't used in a few years and it's a project vehicle. Thought it was the cluster motors and some others were giving wonky values. After replacement, same empty fuel and low fuel light is constantly on, even with a full tank. Wondering if I should start wire tracing or redrop the now heavy tank and replace the sender or fuel pump.

The low fuel light is the clue -- it's either the fuel pump "module" or the wiring. That light is on a circuit that is different from the gauge level circuit. You likely need a fuel pump, but be careful to get the correct one. The Flex Fuel pump is different from the "gas" pump. And don't be cheap; buy a good brand.