Trip computer shows incorrect fuel usage

Hey everybody,

I just got back from a long trip to texas. Ended up putting about 3k on the 2003 truck (w/ duramax) and I noticed everytime I'd fill up, the trip computer would say I consumed about 19 gallons, but when I filled up, it was taking about 24. So, for my 26 gallon tank, the consumption was off by 5 gallons! I need to know if this is a common problem with these trip computers, or if it may be a sign the injectors are starting to go out. My 7 year warranty expires in May, and I'd love to get them replaced under the warranty.

i have the same issue with a 01 grand prix gtp, it'd say i used less fuel than the pump would say i put in, anybody have an answer, don't own the car anymore just curious

Hi,
My wife's 91 seville sts had the same issue.
So the computer knows how many times each injector was activated and computes the useage. But if the injectors are squirting more or less fuel than they are designed for, the results end up wrong. I replaced the injectors on her car and the figures are correct now.
Some times you can do a relearn for the computer and it might correct this.
On her car, I could run a test for injector leakdown and found two bad ones that weren't bad enough to run bad, but did reduce mileage. Also measures the resistance of each injector with a digital meter and found several that were too low. (I guess that made them stay open longer.)
Bob B

Hey everybody,

I just got back from a long trip to texas. Ended up putting about 3k on the 2003 truck (w/ duramax) and I noticed everytime I'd fill up, the trip computer would say I consumed about 19 gallons, but when I filled up, it was taking about 24. So, for my 26 gallon tank, the consumption was off by 5 gallons! I need to know if this is a common problem with these trip computers, or if it may be a sign the injectors are starting to go out. My 7 year warranty expires in May, and I'd love to get them replaced under the warranty.


these injectors have a bad history...and a very expensive one...best get this repaired before the warrantee expires

The question is, is the incorrect fuel usage enough in its own right to make the dealer replace the LB7 injectors? Or is there a greater burden of proof that I need to fulfill?

The question is, is the incorrect fuel usage enough in its own right to make the dealer replace the LB7 injectors? Or is there a greater burden of proof that I need to fulfill?

this needs a injector leak test ...that is what will expose the problem not just the mpg discrepancy

I'm more inclined to have the factory do the leakdown test now. The reason being, my oil is up about half a quart above full with 4000 miles on the oil change. I'm hoping this is sufficient to get the dealer to do the injectors. Any thoughts?

I'm more inclined to have the factory do the leakdown test now. The reason being, my oil is up about half a quart above full with 4000 miles on the oil change. I'm hoping this is sufficient to get the dealer to do the injectors. Any thoughts?

I don't work on these engines but I have friends that do...this is not good as the oil is being contaminated with fuel....could also be very damaging...

I took it to the dealer yesterday. The diesel tech says it's extremely rare that a tiny bit of fuel leaks into the crankcase. Based on my fairly normal dipstick level and the injectors not being over +- 4 on their diagnostic scanner, they declined to service the vehicle further. Looks like I'm gonna have to break it good to get them replaced. Any ideas? I've got till the end of August to break them!

Just thought I would ask, did you go with a larger tire then what came on it? if you did and didnt have it calabrated then that could throw it off. This is my opinion, I wouldnt try to have them brake so I could get them replaced under warranty because with my luck they would die about a month after it expired then I would have to pay for it.

I took it to the dealer yesterday. The diesel tech says it's extremely rare that a tiny bit of fuel leaks into the crankcase. Based on my fairly normal dipstick level and the injectors not being over +- 4 on their diagnostic scanner, they declined to service the vehicle further. Looks like I'm gonna have to break it good to get them replaced. Any ideas? I've got till the end of August to break them!


do an internet search for injector failures with your engine...you will find many ....download and print these and also gather info on the testing technics used to determine this..then go back to the dealer who said , "this is rare" , and watch how his attitude will change....

never do this alone....you must have a witness....this adds to the pressure as now it is impossible for them to deny what was said/done..

The one thing I tried to get him to do was the balance test to see if high return rates existed and he said because it didn't fail the +- 4 test that GM prevents him from even running it. I think he's full of it, and I intend to take it in again mid-summer, assuming my injectors hold up until then. Otherwise I will have a lawyer assist in the matter. In the mean time, do you know of anybody that has had good luck in the Minneapolis area at getting dealerships to do the injectors with little hassle?

The one thing I tried to get him to do was the balance test to see if high return rates existed and he said because it didn't fail the +- 4 test that GM prevents him from even running it. I think he's full of it, and I intend to take it in again mid-summer, assuming my injectors hold up until then. Otherwise I will have a lawyer assist in the matter. In the mean time, do you know of anybody that has had good luck in the Minneapolis area at getting dealerships to do the injectors with little hassle?

I would also get this refusal to do the proper tests in writing...or at least have a witness to back you up, if it is needed...with the legal action you may be forced to take..

try calling the local BBB and tell then that you need to find help resolving this and follow their suggestions....

Lawyers are last resort,,,the best way to avoid unnecessary legal costs is to get everything in wrtting and always back up your case with witnesses....

IF ITS NOT IN WRITTING IT DON'T EXIST...

If the warranty you mention is the special policy for DMax injector failure on the 01-04 LB7, it only applies to a high fuel return rate condition...

Condition
Some customers of 2001-04 model year Chevrolet Silverado; GMC Sierra; 2003-04 Chevrolet Kodiak and GMC TopKick vehicles, equipped with a 6.6L Duramax Diesel (RPO LB7 - VIN Code 1) engine, may experience vehicle service engine soon (SES) light illumination, low engine power, hard start, and/or fuel in crankcase, requiring injector replacement, as a result of high fuel return rates due to fuel injector body cracks, ball seat erosion, or high pressure seal extrusion
This special policy covers the condition described above for a period of 7 years or 200,000 miles (320,000 km), whichever occurs first, from the date the vehicle was originally placed in service, regardless of ownership. The repairs will be made at no charge to the customer.
Important: This special policy only covers the above noted failure modes, which are identified by high fuel return flow.

any other complaint/condition will not be covered under the special policy provisions. To check for high fuel return rates, the tech uses the same hand held device...most likely a TECH II...that was used to look at the balance rates ie...+ - 4 and just commands the fuel pressure to max. If it reaches at least 158 mpa, then there is no excessive fuel return flow and the injectors will NOT be replaced under warranty.

If you brought your vehicle to a GM dealer and stated what you stated here, you should have been informed that there would be a diagnostic charge to verify the condition and what would be required to correct it. If your complaint fell under the special policy provisions, then no diag charge would be charged to you. This is where many of the driving public confuse recalls, special policies and the specifics... and what they should and shouldn't have to pay for.

Just go back to your dealer or even another GM dealer and ask that your truck be checked for fuel in the crankcase. Say nothing else. Like I mentioned previously...its pretty cut and dry to determine whether the return rate is excessive and it doesn't take very long to do. If it is, you'll be covered. If it isnt, expect to pay for the Dr visit. <G>

Good luck