I'm taking my truck in for new rear axle seals tomorrow morning. I believe the guy has a scanner, question is what can we look for and check and what can we change and what should it be changed to?


Can we play with the timing using the scanner and if so what should i set it at? Any help would be appreciated.


I'm not 100% sure here but from some of the posts i've read sounds like i might have an armature problem, sitting idleing for 15 min's or so it'll just suddenly surge for 1/2 second and calm down? Does it to many times to mention during the day. Thoughts?


Fuel delivery? Whats factory? What changes can we make with the scanner only? I won't be getting another opportunity for awhile here.Edited by: CanadianRigger

TDC Offset value - (-.5deg)


Desired and Actual timing - (+3.5deg) Watch this during engine surge incidence.


FS Closure Time for +- 1 least significant digit stability - (1.88ms) Watch this during engine surge incidence.


Fuel rate - (8-11mm3) at idle. Watch this thru engine surge incidence,


Engine Coolant Temperature - (200deg), or so. Watch this during engine surge incidence.


History DTC's for Cylinder Imbalance - does not give MIL.


Any other History codes.


If Boost fooler hooked up, adj to oem setting.Edited by: gmctd

Thanks GM, will see what i can do, hope he knows how to use it. Can timing be changed with the scanner, don't have to move the pump do we?


Foolers not hooked up yet, no bloody time with work! Grrrrrr.......

Snap-on MT2500 can, Tech-I and Tech-II can, majority of others cannot change TDC Offset, but search TurbineDoc's posts - he gives the factory approved method of re-learn without a Tech-II.


Needed if inj pump is adjusted.


Re-check my prev post for further data - I edited it for such.


Coolant temp variation to low can cause Cold Advance, with timing and fuel increase, can appear to be surge.


Closure Time variation can happen with sudden Cold Advance, but if temp is stable, can indicate Fuel Solenoid problems which will cause fuel rate variations.


PCM normally adjusts fuel rate per-cylinder at idle to compensate for changing loads, such as AC on, PS use, change to gear range from nuetral, etc.


Cylinder Balance codes result from this when PCM is unsuccessful at keeping up, for one reason or other. Edited by: gmctd

CR,


Look at the 3 APP values while idling, should be .50v,4.5v,4.0v or so then step on the pedal and notice if the values drop or rise. Drop is normal. A rise is a fault.


If you had the pot. hooked up you could verify it's opperation by watching WGDC ans MAP volts as you very the lever.

Not exactly true, QM - the low voltage increases, the high voltage decreases.


It's to ensure variance is actual demand, and not fault.

CR,


Here is what I did that worked for my 98 GMC may be of use to you


http://dieselplace.com/forum/forum_posts.asp?TID=2688&KW=Turbine+Doc

Well the guy wasn't any good with the Snap-on MT-2500 scanner, didn't have a clue when it came to diesel. Any ways all i got from him was he cleared the codes 236, 237, 238. Not sure here on what they are but we looked at them and it was all turbo stuff, i'm assuming that was from when i was playing with vacuum lines trying to get more boost but chime in here and let me know.


On another note i got the old 95 back from the hospital, seems to run alright but i'm getting code 34 from it now? Whats that one?


Thanks guys


Oh ya, TD to run that learn on the comp do i need a scan tool or can this be done without? I wasn't clear on your post weather it was required or not. Thanks!

34 could be the stepper timing motor is sticking after sitting so long - try running it awhile, see if it clears up.


Second thought, could also be they've left something out of position, and it's interfering with the stepper motor - check down in there with a strong flashlite, make sure no tubing or hose is up against stepper mech.


Passenger-side, between head and inj pump, down low.


You're probably right on the DTC's for the 2000 truck - no MIL means they've healed themselves.Edited by: gmctd

P0236, 0237, & 0238 are all turbo/boost related codes,


0236 is performance delta of 20 kPa from desired


0237 is boost sensor low volt or <40 kPa boost for 10 sec


0237 is boost sensor high volt or > 202 kPa boost for 2 sec

P0236, 0237, & 0238 are all turbo/boost related codes,


0236 is performance delta of 20 kPa from desired


0237 is boost sensor low volt or <40 kPa boost for 10 sec


0237 is boost sensor high volt or > 202 kPa boost for 2 sec





202 Kpa? Thats like 29 lbs of boost? How'd that happen?

pot switch

PCM reads PSI Actual, based on Zero (0) pressure - just subtract Baro from the reading to give correct Boost value.


Values are probably bogus, as you indicated you were altering some things with the system, but could be due to the offset with the 'fooler'

Think of a way that the voltage could spike. The switch resists voltage. More likely short or sensor giving a high reading.

Boost signal voltage would go Hi if open ground.


Signal voltage would go Lo if open +5v.


Loose connector, intermittent wiring connections - happens when doing stuff amongst the various contraptions needed for control and feedback.


PFM, dude.....


P Effin' M........Edited by: gmctd