L67 going into limp home (I think)

[ev351]

HI all,

The L67 in my sierra has had one issue which i am finally going to try to deal with:

Every now and then, and I am trying to figure out when, but every now then it seems to go in to limp home. I have never had another holden do it, so i dont know what it feels like, but basically it almost does not have enough power to get out of 2nd gear at full throttle, it feels like a lot of timing is missing. Also, the rom has been tweaked to enable only one fan to be present and no BCM... this is not the issue as it happens only intermittently.

I had tunerpro hooked while cruising to try to narrow down the issue. At one point i noticed that the performance had gone bad, so i had look through DTCs in tunerpro and could only find one that said ' Malfunction Present - Present' But no other codes were set so I cannot tell what the issue is. Am i missing something? is there a place that error codes are stored in tunerpro so that i can see them later? It is like by the time i look the error has cleared, but its stuck in limp. All I do to clear it is drop power to the ecu for enough time to reset it and off i go again - for a while.

The only thing that i can see strange in tunerpro is one of the paramters that says "Set While Cranking -Set" This is always set, and im assuming that it should only be set while im trying to start the engine? Can anyone clarify what governs this?

Cheers,
\
Ev.

[VX L67 Getrag]

What Base file BIN are you using?

Where is the XDL of when you think it lost power?

You'd know if it's going into limp home by the fact that it actually doesn't move out of 3rd gear!

[ev351]

Oh, So if it goes to limp home, then it gets stuck in third is that correct? In that case i guess its not limp home. What happens is, that you can drive around normally... light throttle and everything is fine, but when you press it hard, the engine gets to about 4 or 5 thousand, and it just doesnt shit out of second, and its not like the box wont shift, its that the engine cant push to the redline so box is just waitong for the right speed to shift, but it never comes.
If I stop and unplug / reset the ecu, off it will go again. full throttle action.

And its hard to track down as its only intermittent. But it sounds like its not going into limp hope from what you have said. I will post the bin that im using if anyone wants to look at it, but i dont think think that it will be that as it has really just had VATS turned off and the fan strategy modified for one fan.

Ev.

[The1]

bin looks ok, post the log up.

[ev351]

Shall do, i left the laptop at work, so as soon as i go back there i will post some logs. Thanks for the input

Ev.

[ev351]

HI all, i finally got my laptop back after the holidays. I have spent some time logging the sierrra, and have posted the results.

So far i have not got a log of it not going properly under full throttle. But i have logged a fault which may shed some light on the subject. The fault is Engine speed sensor. It comes up under full throttle. The only other thing that i notice is that 'set while cranking' is always set. I assume this is related to the 'cranking' input which is pulled low during cranking? if not any input appreciated.

What is Engine speed sensor?

As soon as i catch it not going properly under full throttle i will post another log.

Ev.

[ev351]

AS you can see from the log, the code tha is set is DTC 71, i cant seem to find a code 71 for VS V6.. can anyone shed some light on this?

Ev.

[VX L67 Getrag]

Haven't had a look at the log but from my reference looks like an engine speed low fault code!

Check iac steps & so fourth!

[ev351]

So, does that mean that engine speed sensor is simply RPM? Do you know what conditions have to be met to set this code? The engine seems to be running very nicely so it seems that it would be sensor fault rather than an acutal fault?

[Holden202T]

it could be that the IAC is adjusted wrong and the ecm is trying to make the car idle lower than it will go because the butterfly stop has been screwed in, and as a result it sets a code because it can't get it to desired.

could be something else but that is just an example.

get the engine warmed up and idling in park/neutral and see what the IAC steps are, if its not 10-20 steps or more it may be part of the issue.