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Discussion Starter #1
So I'm posting about 99 K3500. When I got it at the auction the only code that kept coming back was P1656. I've really not done too much troubleshooting yet other than to get the code.

It appears the only reason there is a vacuum pump is to run the wastegate. So if I delete the vac pump and get some sort of wastegate control I should be ahead, but what about the check engine light? I would like to get it to go out, so if other probems pop up...the CIL might give me a heads up.

Basically trying to upgrade and "bombproof" the truck but wondering how this works with the CIL.

Thanks

NH
 

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So I'm posting about 99 K3500. When I got it at the auction the only code that kept coming back was P1656. I've really not done too much troubleshooting yet other than to get the code.

It appears the only reason there is a vacuum pump is to run the wastegate. So if I delete the vac pump and get some sort of wastegate control I should be ahead, but what about the check engine light? I would like to get it to go out, so if other probems pop up...the CIL might give me a heads up.

Basically trying to upgrade and "bombproof" the truck but wondering how this works with the CIL.

Thanks

NH
Adding a Turbomaster, removing the vac pump and a 1" shorter serp belt will eliminate the electronic parts failure portion of the issue but you will need to keep the Solenoid plugged into the electrical system to avoid any CEL on the dash.
You can Tune out the turbo code(s) in the PCM and then disconnect the solenoid.

If you have not already done so, replace the Solenoid with an AC/Delco brand and go from there first.
 

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Discussion Starter #3
Just to be clear, we're talking about this..right?


Ac delco 214-637.

I tend to "blame" this module for the failure because if I clear the code it immediately comes back, even without starting the engine. So you would think that the only thing the computer is evaluating is the electrical signal to the module.

Is my thinking on the right track?

NH
 

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Yes.
 

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Discussion Starter #5
Trying to get my systems knowledge right. A turbocharger "boost solenoid" and the "wastegate solenoid" are the same thing, this is just Autozone doing some funky renaming or something. Right?




No...I'm not going to get aftermarket, just me poking around and being curious and making sure I'm not missing an extra solenoid.

Please confirm I'm on the right thing in the picture. One line goes down to vac pump and one line goes over to the wastegate.

NH
 

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Discussion Starter #6
OK and that's weird. The autozone links changed when I posted them or at least the top one did but it still goes to the "turbocharger boost solenoid".

Not trying to promote AZ, just being clear about the stuff I'm finding and questioning.

Thanks for all the help.

NH
 

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The code will not have any affect, just do as directed by Glagulator.
Hook up the Solenoid to the electrical connector.
The other side to the vacuum pump and disconnect the connection to the turbo.
Not sure if that is valid for the later model year, though.
 

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Discussion Starter #8
So here is a quick update. I put in a new AC delco solenoid and there has been an improvement but I don't think the system is completely fixed.

I disconnected batteries, swapped the solenoids and reconnected batteries. Then started up. I didn't try to clear the code prior to starting.

I shut it down, read the codes and since I saw passed but the history still had a fail I cleared them and thought I was good to go.

I couple of cycles later the CEL came on and I started reading again. The code was back. Sometimes it would clear and sometimes it would immediately come back. Then I started paying more attention to the "last test" status" and history. I was getting results all over the place.

Then I figured out if I cleared the code and then shut the ignition switch off, vice leaving the ignition switch "on" so OBD reader would stay connected, that I could usually pass a test but then later it would fail.

I really couldn't get a reliable/repeatable rhythm going so I decided to go for a test drive and watch "live data". The new solenoid is giving in put and my boost pressure is changing under load. So the system is operating at some level.

Then I tried reading and clearing codes while the engine was running. Now I found a pattern. If I got the engine started, then cleared the would stay cleared for the rest of the drive. Always. (always being the 4-5 times I tried).

Well sometimes I could shut it off and start it back and still get a good code (no code or it would say I passed) and sometimes it would say I failed, but I could clear the code and keep driving, CEL would not come back.

When I was reading codes without starting (key just turned forward), however the system checks itself it "fails" sometimes and "passes" sometimes.

Before it always "failed" and CEL light never went out. Although I didn't press through all these options, but I tried several to see if it was a "hard code" and it always immediately came back before.

So now I know how to clear the code and drive around without it, but sometimes it will come back after a shut down restart cycle and sometimes it won't. However, give it several cycles and it will be back.

So..what "test" does it do with the key forward but engine off. Whatever that is..it often (but not always) fails it.

I'm curious to troubleshoot and understand the system better. What should I do next?

Best,

NH
 

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Discussion Starter #9
Showing some of the various results. Really couldn't get a pattern going if I left the engine off.

Best,

NH
 

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TM will make sure that the turbo works overriding the needs for the solenoid and vacuum pump to make the turbo works.

I don't think it will eliminate the code.
As a matter of fact, in most cases, you will get a Turbo Solenoid code at certain band of speed but at least you know the turbo is working.

One thing about TM, it needs to be set properly.
The seller bought professionally made TM is easier to set since it has the correct spring strength and correct geometry.
The homemade TM will need a lot of tweaking and experiment with different spring to make it behave correctly.
It is easy for people to set the TM improperly and it will create different problems.
 

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Discussion Starter #12
Thanks for the manual. I just read through this. Tomorrow I will see if my scan tool will allow commands of the circuit on and off. So far I'm impressed with the things that tablet will allow me to do.

Anyway, is there any value in getting the engine started and then clearing the codes before driving (assuming I don't get it fixed soon).

I notice something about having a code would set "low power" or something like that in the manual. So perhaps it is trying to "protect" the engine by not powering up much.

Thanks again.

NH
 

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Some code will stay on, some will be off for a while.
Not sure which category the code that you have.

If you feel that it has low power then the code cause the turbo system not to work.

If you want to keep the vacuum system turbo actuator, then you need to troubleshoot it properly.
At any rate, it probably will not affect or ruin the engine.
 

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Discussion Starter #14
Right. If the turbo is not "putting out enough" that would actually be less strain on the engine..righ?

I see some guys have problems when they try to "overboost" the engine. Blow out headgaskets and such.

I hope to spend some time on this today and see if my scan tool can actuate the solenoid.

In my mind I would love to get it back to operating properly for "stock" before trying to modify things and perhaps compound problems or making things harder to troubleshoot.

Thanks

NH
 

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All I know is engine can run without running turbo.
The old 6.2L diesel runs without turbo and it does not put strain on the engine.

Now, the computer can limit the performance if there is a component in the system that is bad.
You need to check everything.
 

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Just thinking again, may be you want to measure the pressure or vacuum ability of the vacuum pump.
Then, make sure there is no leak in the vacuum tube.
Also, make sure you have not reversed the tube connection to the solenoid.
 

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Discussion Starter #17
Here are a couple update videos. Quick update. New pulley, new vac pump and new alternator. Alternator just went out, which got me looking more carefully and found wobbly pulley and suspicious vac pump.

Now you can see in video I get random ground and shorts when revving my engine on the test circuits with one test circuit always staying open.

Isn't there a thread on here with all the ground locations. My guess is that a good next step is to find a clean grounds and see if that cures things.

If not, start tracing wiring.

below is video showing bad pulley


below is video showing test results and changing test results as I rev


Last thought.

When replacing the alternator I found the wire from alternator to the battery had been twisted together and taped with electrical tape. The end on the alternator was 10 gauge and then end on the batter was 14 gauge. I made a new 10 gauge cable with new connectors on both ends.

So..someone has done some "quick" (read shoddy) wiring repairs in the past.

Getting better..little by little. Anyone got thoughts on next steps?



Best,

NH
 

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Discussion Starter #18
Noticed the ESO (engine shutoff test) changes when I rev as well.

I should probably go back and go through all test results to see what changes when I rev.

Best,

NH
 

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Here are a couple update videos. Quick update. New pulley, new vac pump and new alternator. Alternator just went out, which got me looking more carefully and found wobbly pulley and suspicious vac pump.

Now you can see in video I get random ground and shorts when revving my engine on the test circuits with one test circuit always staying open.

Isn't there a thread on here with all the ground locations. My guess is that a good next step is to find a clean grounds and see if that cures things.

If not, start tracing wiring.

below is video showing bad pulley


below is video showing test results and changing test results as I rev


Last thought.

When replacing the alternator I found the wire from alternator to the battery had been twisted together and taped with electrical tape. The end on the alternator was 10 gauge and then end on the batter was 14 gauge. I made a new 10 gauge cable with new connectors on both ends.

So..someone has done some "quick" (read shoddy) wiring repairs in the past.

Getting better..little by little. Anyone got thoughts on next steps?



Best,

NH
Grounds links can be found in the 6.5L FAQ:Grounds-Grounds-Grounds The importance of good grounds.....
I would go through all of your battery cable connections and grounds making sure they are all clean and tight.
Also, go through all of your engine harness looking for worn through wire insulation, corrosion, broken wires.
 

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In my case, I put a 2 gauge wire from alternator to battery on mine.
That is the charging cable.
If you don't want to spend too much money just measure approximate distance of cable needed and go the part store.
They usually have 4 gauge wire ready made battery cable with eye lug connector, that is better than 10 gauge.

A lot of information in the FAQ section on the 6.5L diesel.
You may want to spend a little bit of time each day reading there.
 
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