turbo sensor

[copcarguyP71]

Hi everybody newbie here but have owned our '99 diesel suburban since 2001. Wife got home tonight and said the check engine light was on. I read the comuter and it kicked out the following.

Turbo/supercharger
Boost sensor A Ckt
Rng/perform

Can anyone tell me what this is, cause, repair or troubleshooting? We had the injector pump done in December and I changed the vacuum pump in december as well. I do not think the vacuum would have anything to do with it but I am willing to learn on this one. Thanks fer lookin!:confused:

[copcarguyP71]

Also if it helps the specific code was P0236

[Robyn]

Possible wastegate solenoid issues and or vacuum issues to the solenoid or the wastegate.

Check the vacuum pump to be sure of good steady vacuum (26 inches and steady at the pump)
be sure the lines to and from the pump, wategate, solenoid (On LH VC near the rear) and wastegate actuator are good.
If all is well there then suspect the solenoid.
Could also be a possible fault with the boost sensor on the air plenum.

Hope this helps

Robyn

[copcarguyP71]

be sure the lines to and from the pump, wategate, solenoid (On LH VC near the rear) and wastegate actuator are good.
If all is well there then suspect the solenoid.
Could also be a possible fault with the boost sensor on the air plenum.

Hope this helps

Robyn

LH (ok left hand)...VC? ya lost me on that one.

[copcarguyP71]

OK so I think I pulled the hose connection at the solenoid...drivers side toward rear under the plastic bonnet. I do not have a vacuum gauge but it seems like it has a good bit of suction on the orange hose coming from the pump. I am not sure what the next troubleshooting procedure would be but I cleared the code and I will wait to see if it comes back. Ny further info is certainly appreciated.

[a5150nut]

LH (ok left hand)...VC? ya lost me on that one.

Valve Cover

Check waste gate or movement and check line to waste gate for vacume

[DA BIG ONE]

I have same year and different things happen to give the issue you have;

Maybe your boost sensor (2 bar) is just tellin you of over boost condition to which you can install resistors at boost/map sensor, or JK's boost fooler.

I've knocked around the 3 bar boost/map sensor for awhile now.................

[copcarguyP71]

I hate to be a "parts changer" but I am thinking about just changing out the boost solenoid and vacuum lines since it does not seem like either is big money and see what happens then. Before that I think I will stop by AutoZone and grab up a vacuum gauge just to be sure that the new vacuum pump I installed last month hasn't taken a dump on me. I know there should be 26" of vacuum on the orange line from the pump, is there any way to "trick" the solenoid so that I can check full vacuum at the wastegate actuator?

Any other thoughts?

[copcarguyP71]

Come to think of it back around christmas time I was driving the truck in wet weather (not sure if that matters) and I was having trouble getting boost when I hit second gear. Off the line the boost was fine but a couple of times I really had to mash the pedal to get the boost up after I hit second. That was before I changed the vacuum pump though so maybe unrelated but I am not sure.:confused:

[332bill]

Copcarguy, I had the same issue on my '99 burb. I am pretty certain it was the same code, just a P0236, nothing else. I went through the diagnostic procedure in my shop manual for that code and it indicated it was the the boost sensor on the intake (everyone was saying it was the wastegate solenoid). I replaced the boost sensor (also called MAP sensor by some) and it fixed the problem, no more code. I can scan the diagnostic procedure for you if you want. A warning on the boost sensor, don't buy it from GM. Auto parts stores have it for about 1/2 price.

Bill.

[332bill]

As a little extra info, I was getting good vacuum from the pump, but little or none from the wastegate solenoid. The solenoid was fine, boost sensor bad.

Bill

[Robyn]

Buy the gauge and do the checks real quick just to be sure.
The sensors can and do go south. Better to be sure of the issue before spending the $$$$ :D

The wategate solenoids are known to go away and this can cause a boost failure and the code to set.

Robyn

[copcarguyP71]

332bill...yeah if you could let me know the deal on the diagnostic procedure that would be great.

I reset the codes and my wife drove it for about an hour+ highway and in town today and the code did not come back. This one may be one of those phantom problems but hopefuuly I can flush it out in the open.

[332bill]

Copcarguy, I'll scan it and e-mail it to you, but it won't be until Friday. I noticed you don't have an e-mail address in your profile, so send me an e-mail through my profile and I can respond back.

Bill

[copcarguyP71]

Go ahead and send it to rob@trm911.com

Thanks.

[mitchedo]

I've been troubleshooting a similar problem. I didn't see it mentioned here, and I've never seen it anywhere when I've searched, but the vacuum wastegate actuator should hold 5 inches of vacuum. If you don't have a vacuum gauge, then just suck on the line until the wastegate just closes, and plug it with your tongue and see if it holds. If not, the actuator is wasted. Mine would close if partially closed by hand, but would not hold vacuum. I was shocked at the obscene price for the thing, $389 from the stealer, $235-ish from GM Parts Direct. I got a used one. Most folks replace the factory system with a spring, but I have smog nazis to deal with.

S code engines measure barometric pressure with the EGR sensor; F code engines measure barometric pressure at key-on, engine off using the MAP sensor. Boost is calculated by the difference between the baro reading and the boost reading while the engine is running. A difference of about 3 psi (20 Kpscl according to the manual) from desired (internal to ECM, about 7-8 psi from what I can find) and actual will set the boost code. The shop manual troubleshooting guide has the actuator check before the solenoid check. I'd do that one first, then vacuum checks for the pump and solenoid.

[copcarguyP71]

OK so here's the follow up on the situation. It kicked the code again today so I picked up a wastegate solenoid and replaced it as a matter of course. I also checked the vacuum coming out of the vacuum pump at the WG solenoid. I had 24 inches but I know Robyn had said 26 so is this a big deal for the 2 inch difference? For what it is worth this is from a new/rebuilt pump and not factory new GM piece.

Good info on checking the diaphram of the WG! I will check that next if it happens again. What is the best way around this? I know the spring replacement for this whole mess sounds like a possibility. What are the pros and cons of this system versus the factory vacuum system? Also who makes the best conversion kit for this mod?

Sorry for all the questions but y'all are a bit longer in tha tooth than I am with this stuff.

[Kenneth]

Heath Diesel makes an excellent conversion kit to the spring called the Turbomaster. It sells for about $100 and installs in about 15 min. I have it on my truck and it works great. Although, if you can keep the factory vacuum setup that would be good. In my case, my vacuum system went to crap and I just replaced it with the turbomaster cause it was cheaper. Talk to John Kennedy at Kennedy Diesel and he can explain the advantages of the factory vacuum system vs. the turbomaster.

[copcarguyP71]

Thanks Kenneth! I appreciate the info. Yeah so far I have a new vacuum pump (the old one was totally dead) and a new WG solenoid so I guess I might as well stay the course. Do you notice a performace difference or lag time with the Heath spring kit?

[copcarguyP71]

**BUMP**

Sorry for the bump but does anyone think that the 24" of vacuum I have at idle is a real problem in lieu of the 26" that was referenced earlier in the thread? Since this is a new/rebuilt vacuum pump I would like to know if I need to take it back to the store. Any help is much appreciated.

[JohnC]

24 inches from the pump is fine. You should not (ever) have 24 inches at the wastegate control, though. It should be about 15 at idle.

[copcarguyP71]

OK thanks...I'll check that tomorrow

[mitchedo]

This would be an easy fix if you had a scan tool with the GM add-on pack. I have AutoEnginuity, but I think OBD2 would work just as well for less $$$.

After I replaced the faulty vacuum servo, I diagnosed my problems by watching the following sensors while driving:

Baro
Boost
Wastegate solenoid duty cycle

Turns out my solenoid was a little sticky. I started up the truck and saw it had 0% duty cycle. I whacked it with a screwdriver, and the duty cycle went to 100% and I watched the wastegate close.

Now, while driving, all seems fine. I can't imagine diagnosing the thing without knowing what's happening. I'll replace the solenoid when the weather gets warmer. If the vacuum at the vacuum servo is always too high (your solenoid doesn't do its job) then you would set the code for too much boost. With the scan tool, you can watch the solenoid duty cycle, and boost. The boost should come down as the duty cycle goes down.