View Full Version : Tech 2 ?
Does the Tech 2 tool allow you to modify/calibrate the E-F lines of the fuel gauge?
DmaxMaverick
12-04-2015, 20:30
No, it doesn't. It is a GM fuel gage. You'll have to resort to paper/pencil, or commit the formula to memory. Or, do like the rest of us, and guess.
However, if your needle has just moved out of the blue, to a new range, you can use a Tech II to compare the BCM/PCM reported fuel level % to the gage reading. If the gage matches the %, then the sender is going away. If they are different, then the gage is going away. In any case, the gage is a dumb-slave, and only indicates (supposedly) the % of the fuel level data in an analog display.
Gauge has a 25% error / reading low by 25%
My 07 classic 2500 was dead on, my 07 NBS 2500 has a 25% low error.
DmaxMaverick
12-04-2015, 23:37
Sounds like a tank sender error. Perhaps the float is bent, defective, or something. If it's consistent, but just regularly off by a specific level, I'd suspect the sender. It could be the gage, with the needle off position. Bad parts happen, even when new, on a new vehicle. A check with a Tech II would identify the source.
I think this is the age old "why do I only put 2x gallons in my 26 gallon tank when I refill at the low fuel light" thread.
I believe from a possible email conversation the tank takes 19 gallons from the low fuel light. I don't recall what I add to my 07, but I seldom run to the low fuel light. Not sure if and why the new body style would be any different.
I could recalibrate the gauge to go deeper, but a larger Titan tank (and recalibration) is the ultimate answer. That way you can get the range and still leave several gallons in the tank.
Are there separate sensors for the low fuel light and the gauge indication?
Checking accuaracy of gauge so I have a reference point. It just seems to go down so fast....
Off by 1/4 tank
DmaxMaverick
12-08-2015, 08:14
There is only the one sensor: the fuel level sender in the tank. The "gallons used" in the DIC does not use the sender value, but the "miles remaining" uses the value to detect a fuel fill and fuel remaining. Check this value against what it should be after a full fill. If it seems about right with your average MPG (for previous 50 miles) and actual fuel remaining in the tank, the gage is probably the problem. If it calculates well short, then the gage is likely suspect, but that may not be accurate if it isn't obvious, such as missing 1/4 tank of fuel while parked or stable driving on a level surface.
If that doesn't help......
If it is indicating 1/4 tank less than (actual) full to empty, but is relatively linear, the gage or sender is suspect. You'll need to check the datastream fuel level % value with a Tech II or similar scanner. If it matches the gage indication, the sender is failed/failing. If it tracks the fuel level in the tank, but is about 1/4 different than the gage, then the gage is failed.
The sensor voltage to gallons is mapped out in the ECM which then drives the dash cluster.
Accuracy is only generalized, but good enough in most cases. Now if a guy were to run until empty, then add fuel until the charted voltages are achieved it could be mapped out I guess.
I don't see that we have the attachment upload capabilities that many other forums do or I could upload a screen shot.
The other week I was checking fuel gauge accuracy. Tank = 26 gallons
Used 19 gallons low fuel light turned on gauge pegged at empty. I continued for another 120ish miles until DIC showed I used 24.5 gallons. Then I was getting nervous and filled up.
Dealer told me 4-5 hours labor to diagnoste. At 115/hr ouch.
This is such a Great Group
Can the fuel gauge be repaied or are we talking a whole new cluster ?
DmaxMaverick
12-08-2015, 17:40
OK.
The fuel level and low fuel indicators both operate off of the tank sender. The DIC fuel usage does not, and is only useful for diagnosis if the average fuel mileage and miles remaining are calculated in. If the low fuel message and fuel gage both indicate the same (low fuel message and empty on the gage), but you still have ~7 gallons in the tank, I would suspect the tank sender. While a IPC stepper motor failure isn't unusual, it doesn't look like it at this time. It should be confirmed with a scanner before throwing time and money at it.
4-5 hours to diagnosis a fuel gage issue is insane. It takes me 15 minutes or less, or maybe up to an hour if it's a real bear (wire harness damage, for example). 4-5 hours is enough time to diagnose the cause, then replace the tank sender and IPC, including a couple union breaks and a leisure lunch. Insane.
Alittle ove 1/4 tank left, indicates 13.1 gallon used
At 1/8 left 16.7 gallons used
At E 19.0 gallons used/ 46 mile range/ 18.7 mpg which does not cculate into 7 gallons. Is there anyway to diagnose without a Tech2 tool?
DmaxMaverick
12-09-2015, 01:45
Alittle ove 1/4 tank left, indicates 13.1 gallon used
At 1/8 left 16.7 gallons used
At E 19.0 gallons used/ 46 mile range/ 18.7 mpg which does not cculate into 7 gallons. Is there anyway to diagnose without a Tech2 tool?
Yes. With that info, it looks like a tank sender. I still recommend verifying with a scanner. There are MUCH less expensive options (~$20), than a Tech II. Email me and I'll let you in on the secret.
Alittle ove 1/4 tank left, indicates 13.1 gallon used
At 1/8 left 16.7 gallons used
At E 19.0 gallons used/ 46 mile range/ 18.7 mpg which does not cculate into 7 gallons. Is there anyway to diagnose without a Tech2 tool?
Are there any aftermarket devices, ECM programmers etc on the truck?
H&S?
Truck is all factory, no programmers.
I purchased truck used 07 w/35,000 miles.
Added a Prodigy beake controller for towing.
Have no clue what H&S?
Purchased this year w/35,000 miles
The reason I ask is that most tuners affect the DIC calculations (put not the gauge itself) to the positive side, but some (H&S) seem to skew the opposite direction.
Tell if the truck was tuned prior to my ownership?
Hard to say. Look for obvious signs like exhaust mods. Otherwise all a guy could do is try to read the contents of the ECM and compare to a stock base file.
Are the tech 2 only ac powered?
What is the procedure to get to the fuel levels info on a Tech 2. ?
DmaxMaverick
12-15-2015, 07:44
It is powered through the OBD II diagnostic port (integrated with the connector), or AC/DC with the adapter. To view the fuel level, a simple menu navigation to the data category is all.
If you have an Android device (phone, tablet, etc.), you can use any number of aftermarket OBD II adapters and an app to view nearly all of the vehicle data, as well as read/clear trouble codes. I use, and like, the ELM327 Bluetooth adapter with the Torque Pro app (Google Play Store). Interfuse (ebay) is a decent, inexpensive distributor. There are similar options for Windows and iPhone devices, but the software sucks, is marginally functional, and what does work (painfully), isn't free or inexpensive. Torque Lite (free code reader) and Torque Pro (less than $10) are highly functional and feature-rich.
Are the tech 2 only ac powered?
What is the procedure to get to the fuel levels info on a Tech 2. ?
I thought that I posted, but must not have.
Hard to say where to start, but I guess what I would do is look in the data tables and see if you can find the fuel level sensor readings in volts.
I might try to start with the tank empty. Not that I recommend this, but run until it stops. Add 3-4 gallons or whatever cushion you want and then take another reading. Add one measured gallon at a time and take your readings with each step. I don't think that the voltage readings are buffered, but be mindful of this and watch to see if the reaction is immediate or dampened.
Fuel tank Level remaining 74%
Fuel Level Sensor 1.6 volts
I will test at various levels and post...
That coincides with 18 gallons more or less.
Gauge dropped just 2 needle widths less than 1/2 tank in this next 6.5 gallons used. Should be at 1/2 tank but it is 2 needle widths above 1/4.
Fuel remaining 35%
Sensor Volts: 2.1 volts
8 or 9 gallons remain according to the scale.
The gallons used needs to be treated as an estimate not a hard measured fact. They can vary greatly or they can be spot on.
I see that on the scale at 2.1v should be 8 or 9 remaining. We'll if I go by the fuel used vs pumped back in the gal used meter is very accurate. So would this indicate the fuel level sensor is going goofy or it could be in the gauge. 1/4 tank error is not acceptable to me. I'm hoping I can evaluate without guessing....
Dropping the fuel tank seems to be a PITA if un-necessary.
Thank You
Unfortunately like I stated earlier the only real way to know is to empty the tank add your safe cushion and add a measured gallon at a time and take readings.
You'll want good funnel, a 6 gallon or so can, and a means of measuring/dispensing 1 gallon (or 1/2 gallon) at a time. You could probably use a pitcher for this part. When the big can is empty you'll just have to go for more.
DmaxMaverick
12-21-2015, 08:08
From all the information you've provided, I (still) see this as a problem with the tank sender. Everything lines up, except the actual fuel tank level compared to the indicated level and ECM data. The only "incorrect" data is the actual level, and ONLY the tank sender can produce data for that.
Dropping the tank is a PITA. Removing the bed is less of a PITA (and easier than it sounds). This allows for an easier R/R of the tank sender and close inspection and repair of all the associated connections. You don't have to empty the tank, and the truck remains drivable for testing, etc. during the repair, whereas tank removal requires complete reinstallation and removal (again) to make corrections and/or additional repairs.
I removed and tested sensor:
Results:
52.5 ohms - 200 ohms range
52.5 ohms full tank
5" off bottom of tank, 200 ohms/OL
Is this normal or is sensor range wrong?
I had the meter set on th 200 ohm scale, i must additional test on the 2K scale....
I changed the tank level sensor and all seems normal now.
Thank You for all the input.
How did the metal float arm look? I've seen some come out scary rusty.
DmaxMaverick
01-12-2016, 16:04
How did the metal float arm look? I've seen some come out scary rusty.
That must be a regional thing. Every one I've seen looked like new, or better.
Float arm looked normal / like the new replacement. No Rust.
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