Need Help with DTC`s

[Davis]

I was driving today and the engine missed and then the SES light came on so I checked the codes and then looked them up on the forum and could use some advice on why all the different codes although some of them could have been stored and I did not know it.

Codes are:

18 pump cam ref pulse error
35 inj pulse width error
46 MIL circuit fault
48 int air temp circuit low
49 service throttle soon lamp circuit fault

I checked the codes again with a scan tool to make sure that I was correct using the SES light flash method and I was. So I cleared the codes and rechecked and only 3 of them came back which are :
18 pump cam reference error
35 inj pulse width error
48 int air temp circuit low

The engine still has a long crank time and rattles a lot upon start up and has very low power.(limp mode)

Also the scan tool did show that while starting it lost 8 counts of cam reference each time I would start it.

So is it looking like a injector pump rebuild ??? The current pump has about 86,000 miles on it.

I have checked the grounds and checked plugs with no change.Also read on an old thread that a faulty Optical Sensor filter could cause the codes so I removed it and plugged it in directly with no change. So I cleared the three codes and took it for a drive again with scan tool . DTC 18 showed up at start up and DTC 35 came back but would only show up while the engine was over 1600 rpm not at lower speeds. So now only have two DTC`s 18 and 35. Which are both IP codes. Is there anything else that I could check. Also it is still running in limp mode. Thanks for any advice

[rapidoxidationman]

What happens if you take the Max E Torq E-Prom out of the electronics?

[Davis]

Have not tried that. Why would that affect anything since it has been installed about 8 yrs. Thanks

[Davis]

Finally got around to doing some more diagnosing and also talked with my stanadyne dealer and he added a few tips also.

Went step by step on the DTC 18 chart by GM and according to it all tests lead to faulty optical sensor or circuit problem.

I checked continuity on the pump cam reference wire from PCM to OS harness connector and that is good.

The stanadyne dealer told me to :

1) unplug the OS and run it and check what codes came up that way and it ran the same but had different codes ( 17,43,18)
2) remove the fuel filter and remove fuel in the housing and fill it with fuel conditioner and run it and see if that made a difference . I did but did not change anything.
3) remove the return line at IP and hook up a clear hose to check for air in fuel. I did and there was no air bubbles in the fuel.
4 ) clear codes again and recheck . I did and DTC 18 shows up immediately and 35 will show up when above 1500 rpm.Still in limp mode.

So still looking like optical sensor. I have two old core pumps I bought several years ago . What if I took the OS off one of those and tried it . What is involved with that ?

[Yukon6.2]

Hi Davis
I changed the optical sensor in my tow truck.Really no big deal,i belive i marked them both before removing them,like you i had a core pump to try parts.One day i will go back in and try an optical bump,suposed to give a little better performance???
But i also have the truck slated for coversion to a mechanical pump,oh well the list never ends.
Anyhow do a little searching and you should find all the info you need.
I believe Casey changed his own,and bumped it a bit.
If you have been doing work on your truck,replacing the O/S shouldn't be a problem.
Thomas

[Davis]

Heres an update. I have two donor core DS4 pumps and after finding an article on how to replace the optical sensor while in vehicle that is what I did. I removed one of the top covers on a donor pump and put it on mine and hooked everything back up primed the fuel system and fired it up on 2nd spin so I knew something was already better. I checked the voltage while cranking at the PCM and it was back in spec close to the .5 volt . Also cleared codes and no other codes are showing up and the engine runs great.

[Yukon6.2]

Right On:D
Lots of nay sayers on replacing it yourself.
I had a huge sense of relife when mine started and idled like it was supposed to.
Thomas

[arveetek]

Yes, I did replace the optical sensor in mine, and yes I did the "optic bump" as well.

From my experience, replacing the sensor is doable. However, I would avoid the "bump." While I did notice more power and better throttle response, it messed with the tranny shift timing as well as cruise control. I could never get it where I wanted it. After replacing the injection pump at a later date, I'm back to factory specs and like it that way.

Basically, it made the throttle pedal too touchy.

Casey

[ttpost]

Im in the same boat , do u have a link to the article on sensor replacement ??