DTC 35 and surging

[arveetek]

Had a new one happen twice today:

After work, I started the Tahoe to head home, and she started up normally, and then immediately started surging. RPM's went up and down all over the place, and the throttle seemed to have no input.

I shut the engine off, and then restarted, and everything was normal. After stopping by my folk's house for a bit, I started it up and it happened again. Restarted and everything was back to normal.

I checked codes when I got home, and the only code is DTC 35.

My D-tech FSD recently failed, so I installed my lightly used back-up Stanadyne FSD. I haven't experienced this symptom before, but is this probably another failing FSD?

Casey

[john8662]

Can you see historical codes or are you doing the paper clip?

Historical codes are what you want to figure out what did happen to led to any current DTC's.

Sure, I've had a few PMD's do what you're talking about, including the Solenoid Response time short code.

[racer55]

Often a code 35 can be a failing PMD-otherwise it's IP time-PMD is the cheaper fix first and not a waste since you should carry a good spare anyhow.

[Robyn]

This sure sounds like a failing PMD

How many miles on the IP ???

Seems you have sucked the life out of several PMD's lately ?????


Robyn

[arveetek]

I checked the codes via the paperclip method.

My Dtech FSD recently failed after 5 years. The current FSD is a used low-mileage Stanadyne unit that I keep as a spare. I've intended to order a new Dtech module, just haven't gotten around to it yet.

The current IP is a low-mileage rebuilt unit. Unsure of actual age or miles though.

Casey

[Robyn]

Probably the pmd then

[racer55]

Used PMD's are a crap shoot-they need to be proven by you with about a weeks worth of run time to know if they are good and have 0 symptoms of failure before you can trust 1 for a short time.

The ones I have gotten tended to take a bout 2-3 replacements under warranty before I got good 1's-After the return shipping new might have been better when you can get dormans on amazon for about $120..

[arveetek]

The used one I have was actually installed new by me on the City of Granby's work truck less than a year before the engine lost compression (nobody else could properly diagnose the stalling problem they were experiencing). I purchased the truck from them for parts, and kept the remote-mounted FSD as a back-up.

Even though it is low mileage, it probably has a lot of hours from idling around town....

Getting ready to order a new Dtech right now. I need one regardless of the issue....

Thanks everyone.

Casey

[john8662]

I purchased the truck from them for parts, and kept the remote-mounted FSD as a back-up.

If that's a Grey Module, it's done after being mounted on a remote PMD Cooler anywhere but in the bumper. They only like being mounted on the pump.

I'll bet PMD now for sure.

[racer55]

That is ridiculous-yes its tru that remote PMD's need to be mounted outside the underhood area but they have no clue about if they are on the IP or on a heatsink.

They may require that an additional ground be fastened to the heatsink and a battery ground for extra insurance-but thats all.

[arveetek]

It's a black PMD. I believe it was purchased right about the time the grey units were coming out.

I have a new Dtech unit in hand ready to install. Naturally, I haven't had an issue since those two times on Friday. Still, I don't like being without a spare FSD. I'll mount the Dtech and keep the Stanadyne unit as my emergency back-up.

Casey

[arveetek]

It's been a week since I had any issues. Then today, after lunch, I started up to return to work, and she suddenly went full throttle for just a split second while I was attempting to back up! Talk about making your heart jump! Then she did it again while starting to drive away.

I've read stories about the FSD failing and causing a full-throttle situation, but have never experienced it. Even though it was just for a split-second, it's very unnerving.

I'll be getting the new Dtech unit installed this weekend for sure!

Casey

[ginger743]

It's been a week since I had any issues. Then today, after lunch, I started up to return to work, and she suddenly went full throttle for just a split second while I was attempting to back up! Talk about making your heart jump! Then she did it again while starting to drive away.

I've read stories about the FSD failing and causing a full-throttle situation, but have never experienced it. Even though it was just for a split-second, it's very unnerving.

I'll be getting the new Dtech unit installed this weekend for sure!

Casey

Yup !! A real Heart stopper !

When mine did it and stayed at full throttle I was slowing down to fall in behind a car that was stopped at a stop light , my first thought was , " someone is gonna get killed out here " as I turned off the key !!

Jerry

[arveetek]

Yup !! A real Heart stopper !

When mine did it and stayed at full throttle I was slowing down to fall in behind a car that was stopped at a stop light , my first thought was , " someone is gonna get killed out here " as I turned off the key !!

Jerry

Yeah, no kidding! I prefer the stalling over the full throttle failure!! ;)

I didn't think I was going to make it home this evening... She started normally, and then just as I was about to pull out of the drive, she started doing the full-throttle-back-to-idle shenanigans. I restarted several times, but it wouldn't respond properly. I plugged in an even older FSD (original one that was on the engine back in '05; had it in the glove box, just in case), and then she ran good enough to get me home.

Might have to start packing three spare FSD's with me!

First thing on the agenda tomorrow: install new Dtech FSD.

Casey

[ginger743]

Yeah, no kidding! I prefer the stalling over the full throttle failure!! ;)

I didn't think I was going to make it home this evening... She started normally, and then just as I was about to pull out of the drive, she started doing the full-throttle-back-to-idle shenanigans. I restarted several times, but it wouldn't respond properly. I plugged in an even older FSD (original one that was on the engine back in '05; had it in the glove box, just in case), and then she ran good enough to get me home.

Might have to start packing three spare FSD's with me!

First thing on the agenda tomorrow: install new Dtech FSD.

Casey

I'm still running without a spare but I'm going to order 2 of them. To be sure that they are good before I store them in the truck as spares I'm going to run each one for a month to be sure I'm storing good spares. I don't drive much but a month should be a good test to verify that they are good.

Yup Casey, way to go ! Get a new one in there ! LOL

Jerry

[Robyn]

The full throttle failure is exciting to say the least.

I have had one failure, and it was at home with the hood up testing a bucket full of used PMD'S

Had been through about 5 or so and reached in and gave it a spin, WHAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA PHUT. :eek:

The thing red lined then the ECM shut it off, but not before the entire area around the house was choked with thick black smoke cough wheeeeeez. :D

I have see a couple Burbs go wild in the Grocery store parking lot too.

The one was hilarious, young gal had loaded the groceries in the back of the Burb, climbed in an lit the fire, Whhhaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa.

She had it in drive just as it went crazy, damned thing got over against a concrete light post base and there it sat, engine howling, black smoke pouring out and the rear tires screaming in protest.

Looked like a Friday night burnout contest.

Poor little sweetheart was scared to death. luckily she had a the driver window down.

Two of us ran over and screamed at her to turn the key off, noooooooooooooooooooo, she was way to far into white knuckle fever to even hear us.

The rig was tight against the post and not going anyplace, so I ripped the door open (thank gawd it was unlocked) stuck my hand in and shut it off.

The dude that was with me was white as a ghost, and the little gal in the rig likely needed a change of panties.

The entire lot was covered with a huge cloud of thick black smoke from the roaring beast.
The 30k miles off the rear tires added to the stench too :eek:

After the beast had been vanquished, I broke into nothing but giggles for the next hours off and on.

Her Hubby/BF or ???? had installed a 4 inch exhaust on the thing, and all the while it was trying to tear the world apart, it sounded awesome., with a deep throaty growl.

Took about half hour for the fire med boys to coax the gal from the rig.

A friend of mine heard the racket and came over to see WTF

He has a GM 6.5 and had a spare PMD.

The gal was from Seattle and the Burb was the ride home.

The PMD was on a remote on the manifold, so we swapped the PMD and switch the resistor.

Purrrrred like a kitten again

Gave her a 15 minute lecture on the ways of the force, and to just hold the brake and turn the key off, noooooooooooooo biggy.

She was not real sure about all this stuff, but calmed down and got back in and started the truck.

After a couple laps around the lot to get her confidence she headed out.

All's well that ends well eh ????:)

Fortunately, the full on failure is far more rare than the stall/fail to start type.

Many GM techs have never seen a full throttle failure.

A couple years ago the local GM dealer had one go off in the shop and fill the place with smoke and scare the hell out of everyone.

Life with an electronic 6.5 can be interesting to say the least.


Missy

[arveetek]

New Dtech FSD installed. Running better; easier starts; less smoke on startup. I'll keep ya updated.

Casey

[Robyn]

Happiness is a fresh PMD :D

[arveetek]

New Dtech FSD and I haven't had a single issue all month. She's running great!

Casey

[Whitectc86]

New Dtech FSD and I haven't had a single issue all month. She's running great!

Casey

sounds like you have other issues though, have you changed your fuel tank sock or dropped the tank to check it at least since you've been through at least 2 pmd's?

[phantom309]

sounds like you have other issues though, have you changed your fuel tank sock or dropped the tank to check it at least since you've been through at least 2 pmd's?

Eh???????

maybe change water pump too right? :D

[Whitectc86]

Eh???????

maybe change water pump too right? :D

Just preliminary checks for codes 35 and 36

Fuel System Air Leak Test
1. Install a transparent hose between the fuel manager/filter outlet and injection pump fuel inlet.
2. Start and idle the engine, observing the fuel for air bubbles.
-- If air bubbles are not present, stop the engine and go to step 6.
-- If air bubbles are present, stop the engine and go to step 3.
3. Check the lift pump suction line for air leakage:
-- Disconnect fuel pipe from the fuel sender and plug it.
-- Disconnect the fuel pipe from the lift pump, and install a hand held vacuum pump with gauge.
-- Apply vacuum to the fuel pipe and observe the gauge reading:
--- If vacuum does not drop, connect fuel pipe and go to step 4.
--- If vacuum drops, repair the air leak in the suction line and install the suction line pipe and hose.
4. Check the fuel sender for air leakage:
-- Remove the fuel tank.
Remove the fuel sender from the fuel tank, remove strainer and plug the bottom of the pickup tube.
-- Apply a vacuum to the upper end of the pickup tube, and observe the gauge reading.
--- If vacuum does not drop, install the fuel sender and fuel tank.
--- If vacuum drops, replace the fuel sender, install the fuel tank, connect the fuel pipe and go to step 5.
5. Start and run the engine, observing the fuel for air bubbles:
-- If air bubbles are present, stop engine and recheck steps 3 and 4.
-- If air bubbles are not present, stop the engine and go to step 6.
6. Remove the transparent hose and connect the hose of the fuel manager/filter outlet to the injection pump inlet fitting.
7. Disconnect the return hose from the injection pump.
8. Install a transparent hose between the injection pump and the hose of the return line.
9. Start and run the engine, observing the fuel for air bubbles:
NOTICE: It is OK to see a small stream of air bubbles on snap acceleration
-- If air bubbles are not present, go to step 10.
-- If air bubbles are present, replace the injection pump.
10. Stop the engine.
11. Remove the transparent hose and attach the fuel return hose at the injection pump.
12. Clean any fuel spillage.
13. Run engine and check for fuel leaks.



FINAL STEP- CLEAR DTCs

[arveetek]

sounds like you have other issues though, have you changed your fuel tank sock or dropped the tank to check it at least since you've been through at least 2 pmd's?

Been running fine since the PMD swap almost a year and a half ago.

You'll have to check my other threads to see about the fuel tank sock fiasco I had before that. Long story short, an aftermarket sock sucked shut while driving, causing fuel starvation symptoms. After shutting the engine off, it would relax and allow fuel to flow again. Took me several months to figure that one out. Put an OEM sock back in, and all is well.

By the way... I've owned this rig for 10 years, and have gone through 3 or 4 PMD's and one injection pump. I'm at 298K miles as of today.

Casey