Wont go into closed loop

According to my ultragauge, my truck always stays in open loop and never reaches closed loop. However, other than the indicator on the display, there don't seem to be any other effects. I am averaging 20 mpg and as far as I can tell there is no lack of power and the check engine light is not on. Any idea what could be keeping it from getting into closed loop? or if it doesn't seem to be having any negative effects, should I not worry about it?

 

They are suppose to run in a closed loop... You may not have any negative effects (that you notice). How many miles on the truck? A open loop could be caused by many things... o2 sensors, vacuum leaks, bad plugs/wires.. When was the last time you checked these?

 

It has about 163,000 on it. I bought it around march with 155,000, and I haven't checked any of those myself yet. I'm not all that mechanically inclined, kinda learning all this stuff as I go.

 

when I'm on the throttle heavy, my UG shows that I'm in open loop, but when under normal driving (moderate throttle) it is closed. No adverse affects that I've noticed, but I'm sure its due to my o2 going bad..

 

When you go heavy into the throttle you will typically go into an open loop. Closed loop operation is typically for light throttle or idle condition. Lack of going into closed loop can be, as mentioned, due to not getting the correct feedback from several sensors, including O2 sensors, MAF sensor, air intake temp sensor (Part of the MAF sensor assembly usually) as well as the ECT sensor.

 

I typically go pretty light on the throttle for the sake of mpgs. If its not going into closed loop at all, what should I check first?

 

I would suggest looking at hooking up a scan tool to look at the data. See if something looks out of place.

 

used my ultragauge to check for any codes, and it turned up P0128. Its been showing that same code as long as I've had the truck, and my temperature gauge on the dash is also not functioning. I had it checked out by a mechanic a while ago, and was told that it was only showing that code because the gauge on the dash wasn't working, so at that point I just left it alone. Now I'm wondering if maybe that has something to do with the open/closed loop issue?

 

DTC No. P0128

DTC Detection Condition:
(a) Cold start
(b) After engine is warmed up
(c) Engine coolant temp. < 75C (167F)

Trouble area:
Thermostat
Cooling system
Engine coolant temp. sensor
ECM

If your engine isn't (or doesn't think it is) warming up, I don't think it will go closed loop.

 

The code is not because the gauge is malfunctioning... not exactly.

The gauge is possibly malfunctioning because of a faulty sending unit.
This seems to be confirmed by the code.

What does the UG indicate your temperature to be? A disconnected or bad sending unit could be the problem... or someone may have installed a 155 degree thermostat.

Quite often, when a vehicle has overheating problems, the owners will install a "cooler" thermostat thinking it will help (and it won't). People will also install cooler thermostats out of ignorance, thinking that cooler is better. It's not. An engine is most efficient when it's running on the edge of meltdown.

 

Makes sense I suppose...tomorrow I'll check the temperature through the ultragauge and see if it jumps around like the gauge on the dash

 

You sir, have the ultimate Split second tuning truck...

 

Mine will maintain closed loop under some pretty heavy acceleration.
Checking it out tonight on the way home climbing some hills, I had to hammer down enough to downshift AND get the engine to 3k before it went to OL.

On the bottom end, I haven't thought to look at idle, but it'll remain in CL on decel until it drops below 1900 at zero throttle. From there, "it depends".
If I'm just off the gas but slowing gradually (level or a slight decline), it'll stay in CL until 1500 when it drops into OL. If it's down a steep hill, then the engine braking kicks in and it drops into OL at 1900, but if any throttle is applied, it immediately goes back into closed loop.