Fuel trim cell

[DnI]

Hi long time member first time post i search and usually do find what im looking for, but can anybody tell me where the fuel trim cell reading should be at i got an 03 trailblazer with a I6 thanks ain advance:thx

[PROSPHOTO]

The ideal # is 0 an any cell, which indicates your air/fuel ratio is 14.7 : 1 (Stoichiometric air-fuel)

A positive fuel trim value indicates the control module is adding fuel in order to compensate for a lean condition by increasing the pulse width. A negative fuel trim value indicates that the control module is reducing the amount of fuel in order to compensate for a rich condition by decreasing the pulse width.


BTW...under User CP, please click "edit profile" & fill out all of your vehicle information for us :cool:

[DnI]

so if it suppose to be at 0 mine is at 22 how do i make it go back to 0 or is that impossible

[PROSPHOTO]

I'm guessing that's your long term fuel trim that's at 22.

You have to find and repair whatever is causing your lean condition, that's how you can get it back to 0 :yes:

Is your check engine light on? What prompted you to check your fuel trim?

[DnI]

i checked at work with the genesis reader and it was reading at 22 no check engine light i checked it cause im only getting like 10 mpg

[PROSPHOTO]

Your only getting 10mpg b/c the truck is dumping a much greater amount of fuel than normal to compensate for a lean running condition...it is possible that you have a lazy O2 sensor that's reading more on the lean side than it should. Next time you get your hands on the scanner, check the O2 sensors and make sure the #1 sensor is switching rapidly and evenly above and below [approximately] 450mV.

Before getting your hands on the scanner, check for any vacuum leaks under the hood :yes:

What engine/performance mods are done on your truck (if any)?

[ds8]

My interpretation of your problem is that you are reporting the fuel trim cell number as 22. If you are in FTC #22, you are operating open loop. That is why you are getting terrible mileage. Long term fuel trim and short term fuel trim are different things and they correct the fuel supply, but are not the same as fuel trim cell number. I'm not sure why you are in open loop. More information is needed.

DS

[AbsoluteZero]

On one of my GM vehicles the system would only correct +/- 20%. Haven't looked up the I-6 spec... If he's running in open loop for any period I'd think he'd get a DTC plus I'd think whatever scanner he's using should be able to determine if he's in open loop....

[ds8]

PE mode runs in FTC #22 and does not cause an error code, and if the conditions in table B0936 (Closed Loop Temp Enable are not met), no code will be set (unless there is a timer running too). These two things point to possible continuous PE mode operation, or an open thermostat/failed coolant temp sensor. Without more information, it is hard to tell what is going on. Have you been tuning your PCM?

DS

[DnI]

What other imformation do you guys need i have done no mods all stock for now i want to fix this promblem first before i go foward with mods. I will see if i can get a print out. i did get a temp sensor for the same reason ds8 said i will be doing a coolant flush and replace the thermostat also.

[DnI]

ok my fuel trim is at 22 in idle one i drive it drops to like 10 to 15 and my o2 sensor reads at 600's at idle and then drops 40's then at 800's at a slow rate. my co worker told me that i might have to reflash my ecu or get a new one what do you guys think

[ylab]

so if it suppose to be at 0 mine is at 22 how do i make it go back to 0 or is that impossible

At 22, you probably have a massive vacuum leak somewhere in the system....almost has to be. An injector failure should have set the CEL by now with the trims that high. I had the same issue with my Taurus a couple months ago and didn't know it until the CEL started coming on. You'll only get the CEL when the leak pushes the fuel trims beyond the ability for the PCM to compensate or over a preset limit....usually around 22-24 on most cars. (The raw numbers should be under 5-6, with typical numbers of .6-1.0 for a healthy engine. (GM runs these things a little rich to begin with).

Update: Just saw the last post, is that 22 when you first start the truck cold or warmed up, but just idling? (Little bit of confusion there, but the trims are still farther out than they should be). When COLD, the trims will shoot up until the coolant reaches operating temp and the O2 sensors come on line.

[DnI]

thats after an hour of driving fuel trim still at 22 at idle and injectors read that they all i believe at 3.00 or somthing like that per seconds if i remember right but all injectors where firing at the same rate