Need help with some codes

[Burbanaz]

Still getting DTC codes, driving me crazy especially because i keep wanting to use cruise control on trips but cant because of the SES light. Also i worry about reliability issues with my injection pump.

27-Accelerator pedal position sensor circuit fault
35-Injection pulse width error (pulse width short)
36-Injection pulse width error (pulse width long)
78-waste gate solenoid fault
72-vehicle speed sensor circuit fault (trans output speed)


Ive been trying additives for the last 3k miles hoping that it would clear up the codes 35 and 36 but nothing, so im thinking that my inj pump is just shot unfortunately unless anyone can think of anything else for me to try. Even though it drives perfect, starts great and has no drive ability issues at all. I replaced the waste gate solenoid thinking that would clear up the code 78 but im still getting it. It doesnt make any sense to me because i have a heath turbo master so i dont know why im getting a code 78 since i thought it just needed to have the solenoid on there to compete the circuit. I dont even really know what the code 72 is referring to so im going to have to look around. Code 27 im guessing i need to replace the accelerator pedal position sensor, does it only come as the whole pedal assembly?

 

[NVW]

Don't replace anything yet. First thing to do is check the grounds. http://www.thetruckstop.us/forum/showthread.php?17457-Grounds-what-are-they-amp-where-are-they

The code 36 is likely the one affecting cruise. A pmd can cause 35 and 36.

What model truck is it? What is the 8th vin #. F or S

 

[WarWagon]

You need to look at wiring and X2 on grounds as said above. After you price the Accelerator Pedal Assembly (APP) $$$! for code 27 I guarantee you will be checking wiring and grounds with a fine tooth comb. Also check the positive and negative battery cables as they like to soak up battery acid and corrode internally. I would also pull and clean fuse contacts.

Code 78 is boost like 6 PSI off the computer internal table. A Turbomaster without a tune can do this. Even with a tune and different turbo I can still get a code 78 now and then. Again it just means boost is out of range and the dumb computer doesn't know "why".

Your other codes can be from air in the fuel. Have you tested the lift pump and OPS per the thread in the technical library?

 

[handcannon]

Putting a boost fooler on would stop the code 78. You can very easily make your own boost fooler for less than $10. The main component is a 10K ohm potentiometer from Radio Shack, with a few inches of wire and crimp on wire connectors.

I just happened to remember that I have some pics from when I did my boost fooler.

Pic 1--- This is the ground wire for the pot, which I just put on one of the mounting bolts.

Pic 2--- The boost sensor is the black box that is on top of the upper intale hat. It is just slightly smaller than a deck of cards. There are three wires in the wire loom connector and the green wire in the center is the one to cut and wire the boost fooler in to. I used bullet connectors so that if in the future I want to remove the boost fooler all I have to do is disconnect the fooler and re-connect the wires.

Pic 3--- This shows the back side of the completed, and installed, boost fooler.

Here's a link. Post #3 has a wire diagram for the boost fooler.

http://www.thetruckstop.us/forum/showthread.php?589-6-5-Diesel-Technical-Library&p=61390#post61390

ps: this is for 94 and 95 OBD1 vehicles.

 

[Burbanaz]

Don't replace anything yet. First thing to do is check the grounds. http://www.thetruckstop.us/forum/showthread.php?17457-Grounds-what-are-they-amp-where-are-they

The code 36 is likely the one affecting cruise. A pmd can cause 35 and 36.

What model truck is it? What is the 8th vin #. F or S

yea i was thinking either the 35 or 36 were causing it because the SES light will come on at like 1800 rpm and go off under the speed. Its a 1994 k2500 Suburban 8th is F

You need to look at wiring and X2 on grounds as said above. After you price the Accelerator Pedal Assembly (APP) $$$! for code 27 I guarantee you will be checking wiring and grounds with a fine tooth comb. Also check the positive and negative battery cables as they like to soak up battery acid and corrode internally. I would also pull and clean fuse contacts.

Code 78 is boost like 6 PSI off the computer internal table. A Turbomaster without a tune can do this. Even with a tune and different turbo I can still get a code 78 now and then. Again it just means boost is out of range and the dumb computer doesn't know "why".

Your other codes can be from air in the fuel. Have you tested the lift pump and OPS per the thread in the technical library?

Ill go over wiring today and check my grounds. If the code 78 isnt the one kicking on the SES light it really doesnt bother me. I only have like 6-8 lbs at full throttle, i have the turbo master adjusted and a boost guage so i know im not running any dangerous boost levels or anything. I have recently replaced the lift pump because it wasnt working and replaced the OPS, is there another way to get air out of the system besides the normal bleed procedure?

Putting a boost fooler on would stop the code 78. You can very easily make your own boost fooler for less than $10. The main component is a 10K ohm potentiometer from Radio Shack, with a few inches of wire and crimp on wire connectors.

I just happened to remember that I have some pics from when I did my boost fooler.

Pic 1--- This is the ground wire for the pot, which I just put on one of the mounting bolts.

Pic 2--- The boost sensor is the black box that is on top of the upper intale hat. It is just slightly smaller than a deck of cards. There are three wires in the wire loom connector and the green wire in the center is the one to cut and wire the boost fooler in to. I used bullet connectors so that if in the future I want to remove the boost fooler all I have to do is disconnect the fooler and re-connect the wires.

Pic 3--- This shows the back side of the completed, and installed, boost fooler.

Here's a link. Post #3 has a wire diagram for the boost fooler.

http://www.thetruckstop.us/forum/showthread.php?589-6-5-Diesel-Technical-Library&p=61390#post61390

ps: this is for 94 and 95 OBD1 vehicles.

on mine is a 95 OBD1 vehicle so this should work and i already have this stuff laying around in a drawer in my garage so ill probably throw this on there. Thanks.


Thanks for the advice everyone, ill try all this stuff and hope it clears some of these codes up. The 35 and 36 are the ones that worry me the most, im hoping i wont have to replace the inj pump.

 

[WarWagon]

Put a clear return line on the IP to check for air. Do this before changing the IP as air causes all kinds of issues. A PMD can also affect pulse width as it controls this...

 

[Burbanaz]

went through a bunch of the grounds today and cleaned them up. The straps from the block to the frame are completely covered in crud from oil or something leaking all over them, would that effect them since they uncoated braided straps. I guess ill try and see if i can find a PMD maybe used or something. I wish i knew someone else with a 6.5 then i could just try it and see if thats the issues before i spend the money on a new one.

 

[Will L.]

Yes, remove and clean the braided ground straps. I had ECM/bcm problems in a gasser last year and that turned out to be the problem. The contact areas were fairly clean so it had to be the oil on the surface of the wire causing it. Electricity flows on the exterior of the wire not in it (think opposite of a water pipe). That is why a stranded wire handles more heat and current than a solid wire of the same mass.

 

[JMJNet]

PMD is never a wasted expense. IMO.

It will fail one way or another, we always suggest that people have one KNOWN WORKING PMD as spare anyway.

Who follow common sense this day!!! Look at the government of the greatest procrastinator nation in the world.

 

[Burbanaz]

Yes, remove and clean the braided ground straps. I had ECM/bcm problems in a gasser last year and that turned out to be the problem. The contact areas were fairly clean so it had to be the oil on the surface of the wire causing it. Electricity flows on the exterior of the wire not in it (think opposite of a water pipe). That is why a stranded wire handles more heat and current than a solid wire of the same mass.

Ok ill clean them and if their damaged replace them. Cant hurt.

PMD is never a wasted expense. IMO.

It will fail one way or another, we always suggest that people have one KNOWN WORKING PMD as spare anyway.

Who follow common sense this day!!! Look at the government of the greatest procrastinator nation in the world.

I never said it was a wasted expense, just hard to spend 300 bucks on something that may or may not be bad. Im going to buy one though and try changing it and if it is good still atleast ill have a backup

 

[NVW]

http://www.leroydiesel.com/Page_2.html

$210 without a heat sink.

 

[Burbanaz]

thats not bad, ill order one

 

[NVW]

The old black Stanadyne PMD's use the same extension as the Flight Systems (Dormer), the new Stanadyne (grey) use a different extension. Make sure what you have is compatible with the new one.

 

[Pruittx2]

I got mine from peninsular diesel on Ebay,, ext cable on Ebay,, and heat sink on ebay. $199,,, $20 $15
and put it up behind License plate. Done. Also consider the battery cable mod.

 

[Burbanaz]

Put a clear return line on the IP to check for air. Do this before changing the IP as air causes all kinds of issues. A PMD can also affect pulse width as it controls this...

Any ideas what clear line to use? does it need to be anything special because its flowing fuel? If there is air in the system is there a different way to bleed it besides the normal method when changing the fuel pump.

 

[WarWagon]

Hardware store and get any clear tubing 1/4". This is a temp thing for testing.
You either have a bunch of air bubbles flowing through, air, empty line from sitting overnight, or no issues. Once you bleed the system it stays free of air. Or you have a air problem. The system doesn't need a prime as the return line is also submerged in fuel.

Ideally you have nothing but clear fuel in the line and the next morning it is still full of bubble free fuel. After startup you may get bubbles with a minor issue.

 

[ak diesel driver]

my temp clear line has been on for several years

 

[handcannon]

Mine also.

Don

 

[Will L.]

I usually get my clear line from a local Stihl chainsaw dealer. It is actually slightly yellow, and called tygon fuel line. It is rated for gas, diesel, ethnonal. Another option is aircraft fuel line can be ordered clear (just google). Then the line can be left permenent.