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Discussion Starter #1
Ok, so after spending the past week searching and digging through everything I could find online, I’ve decided to try my luck here.
I commute daily in a 2006 IRL with a zzp stage 2 setup with roughly 186k miles.

Driving home normally, decide to pass a few folks before I hit my exit on the interstate... felt very weak and noticed it was only making around 2-3lbs of boost per the factory gauge.

I’ve replaced all the vacuum lines for the boost control solenoid and bypass valve, as well as the solenoid and valve itself. I’ve used my scan tool to change the duty cycle for the solenoid to 10% per the shop manual and the valve does not actuate. This lead me to check the electrical connector for continuity, which it does not have while the car is idling. Also, the bypass valve is closed, when it says it should be open. If I remove the vacuum line from the back of the solenoid and plug it (aka the bypass mod) the bypass valve opens fully at idle and builds boost while driving like normal.

Anyhow, it’ll pull a code (PT33) for the solenoid if I disconnect it while running and freeze all the sensor data for the other parameters that the PCM needs and they all fall within specs.

All my engine grounds that I can see look good, am I missing a ground or something in between the wiring where the boost control solenoid goes into the PCM itself? The fuse for Boost in the fuse block is good. I’m sort of at a loss at this point... any help would be greatly appreciated.
 

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Are you positive you got a good solenoid when replaced?
Maybe the diaphragm is stuck closed. Have you tried adjusting that?
 
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Discussion Starter #3
Are you positive you got a good solenoid when replaced?
Maybe the diaphragm is stuck closed. Have you tried adjusting that?
I’m pretty sure the solenoid is good, used a 9 volt battery to check it and it open and closed with no issues. It and the bypass valve are both brand new ACDelco parts.

As for the diaphragm, it moves freely when hit with vacuum or when the solenoid is bypassed.
At this point, it seems like the wiring to the solenoid has got to be the issue... there’s not continuity across the terminals at idle, the PCM is communicating with it (at least partially) because if you unplug it, it’ll throw the PT33) code.
 

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Did you recently do the stage 2?
I'm wondering if its a pcm issue? Did you send them your pcm first?
 

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Discussion Starter #5
I think it’s been a Stage 2 for about 3 or 4 years at this point. With the scan tool, all the checks of the PCM itself come back fine, but I may be missing something.

I got a chance to measure resistance in the old boost solenoid, which was about 3ohms, the new one is around 25, so maybe that was the original problem. I also used a vacuum gauge and pump to test the lines and values in the boost system, everything is fine physically.

It seems like the signal from the pcm to actuate the boost solenoid is either too weak or isn’t getting to the switch itself. As long as the solenoid is plugged in, no DTC’s are set, if I unplug it while the engine is running it throws the PT33 code.
 

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Interesting. Wonder if it runs through a fuse? I'm not near my redline otherwise I'd trace some wiring.
The quick searches I did showed either the diaphragm or the sensor itself
 
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Discussion Starter #7
Interesting. Wonder if it runs through a fuse? I'm not near my redline otherwise I'd trace some wiring.
The quick searches I did showed either the diaphragm or the sensor itself
Yeah, beside the boost fuse at position 14 in the fuse box, I can’t tell where the wiring runs. I’d guess my next thing to do is chase the wires back to the fuse block and then figure which pin it goes back to the ecu. I ordered a new connector and pigtail for the boost solenoid, maybe that’ll help. Strange stuff.

Thanks very much for your help, it helps having another perspective on this deal.
 

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The vacuum line plugged in the right spot? Iirc it goes in the top. Bottom is plugged. From the front side.
Any time man. It what were here for
 

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Discussion Starter #9
Yeah, vacuum lines seem to all check out. I’ve tried the trouble shooting method from the FSM for the boost system and everything physically and vacuum wise works correctly.

I’ve traced the signal wire to the pcm, seems like that is the issue. The Ignition 12v signal is good on the connector to the boost control solenoid, for some reason it looks like the control signal is not coming from the pcm, or at least it isn’t changing from 12v when I change the duty cycle of the solenoid. I’m color blind, so wiring stuff is a challenge. I’m thinking I may pick up a used pcm, get zzp to reflash it and go from there.
 

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Discussion Starter #10 (Edited)
Ok, so finally got few minutes to try to troubleshoot some more. After going through everything again, I think I’ve found the issue.

At idle, the boost control signal (from the pcm) is sending 14v, closing the boost solenoid which causes the boost bypass valve to close on the supercharger. It’s supposed to be fully open at idle (which means the boost control solenoid should have power from ign1 and nothing from the PCM, I think). To verify this I removed the PCM signal wire from the boost solenoid and substituted a wire to ground. This keeps the solenoid open, which causes the bypass valve to open at idle like it should.
Now my question is how is it getting the 14v signal from the pcm all the time? Is there a short or something in the pcm itself? I’ve probed the wire at the pcm connector and it’s the same voltage it is at the boost solenoid connector...

Anybody have any idea? Thanks.

Also just sent an email to zzp to see what they think, so hopefully can post their reply soon to hopefully help someone else looking at this at a later time.
 

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It almost seems like there's a short or a break in the wire and its not being grounded correctly so it's full voltage all the time.
Maybe zzp will be able to further see looking at the files.
I'm hoping this is the issue. Maybe try adding another ground to the pcm itself?
 
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