Code P0640 for 1995 SC

I'm trying to help a friend with a 95 SC and has a code P0640.
It is a quad driver circuit but don't know which 4 circuits are involved for troulbleshooting.
Unless I can use my 98 FSM.???

P1640 QDM circuit. P0640 doesn't exist.
schematic


flow chart


Hope it helps Rick.....

Did I write down the wrong Number.?
Dyslexia can now be added to my list of ailments.
Thanks a lot Scott, no wonder I couldn't find out anything on this.
The Actron Scanner that I used on the 95 to pull the code, does just that- give you a code with a very brief description.
Is the above data from AllData or Mitchell's.??

The guy I'm helping with this is a Foreign car Technician and a very good one. But when he accepted this Riv. in for what he thought was going to be a simple diag by hooking up his Snap-On equipment, he found he didn't have the key or what ever was necessary for him to down load data from a 95 Riv with OBD 1.5.
He took it in knowing he had never had a problem with my 98 as far as hooking up diag equipment and reading the issues.
He didn't know anything about GM's OBD 1.5 though.
So I agreed to diag and do as much as I could to repair this if he changed my LIM gaskets.
He just did Heads on an NA Oldsmobile with a 3800 last week and because that was so easy, he said yes without hesitating.
Wait till he finds out just how much more work my car will be.
Less room in the engine bay and having the S/C make a big difference.
But a deal is a deal.
Anyway thanks very much for the info and hopefully I can pinpoint the problem on this 95 quickly without the use of a Tech 1.

If you have a boost gauge on it and are only seeing 4-5 psi max, then its the boost controller. If its the full 7-8 then its one of the other three.
(I've had the same code in the past, for me it was the boost solenoid)
As to if you wrote it wrong, I have heard of the 1.5 throwing codes that don't exist, but refer to the closest "legal" one)

Thanks Karma.
If I should run into any issues do have the 95 FSM Book #2 ????

Rickw wrote:

Thanks Karma.
If I should run into any issues do have the 95 FSM Book #2 ????

I wish I had it, does Abaddon?

He has access to either Alldata or Mitchell's or both. not sure.
I think this guy, who has the car in his shop, has AllData. It should be enough as long as they don't keep calling out the use of a Tech 1 to activate certain things while trouble shooting.
I can do a work around with some jumper wires if I'm careful and disconnect the PCM first.

I have Mitchell btw.....
It's funny....on '96 and older cars I can copy and paste schematics and flow charts. '97-newer I can only paste flow charts, as the "newer" schematics (Mitchell's) are in full color and require an SPD viewer which I had to dl to my comp.

Np on the help. GL!

Rick,

Have a look at the code 1640 write up i did you will find more info on how to diagnose the solenoids.

https://rivperformance.editboard.com/series-i-scans-tuning-f14/write-up-series-i-code-1640-finding-a-fault-t6819.htm#101917

Nigel

Abaddon wrote:

I have Mitchell btw.....
It's funny....on '96 and older cars I can copy and paste schematics and flow charts. '97-newer I can only paste flow charts, as the "newer" schematics (Mitchell's) are in full color and require an SPD viewer which I had to dl to my comp.

You mention the need to download this SPD viewer.
This explains why I can only print certain stuff from Mitchell's, the rest can only be viewed. I thought it was my penance for bootlegging.
Could you steer me in the right direction for this download and then hopefully I'll be able print some stuff here, at home, as i have access to Mitchell's for all years and be able to print and bring copies to the job.
Thanks again,
Rick

nigelf wrote:

Rick,

Have a look at the code 1640 write up i did you will find more info on how to diagnose the solenoids.

https://rivperformance.editboard.com/series-i-scans-tuning-f14/write-up-series-i-code-1640-finding-a-fault-t6819.htm#101917

Nigel

Nigel,
Thank you very much for sharing your experience with this code.
Hopefully I'll be able to follow what you did and solve this problem as well.
Cheers,
Rick

I read in Nigel's thread that the boost control solenoids are no longer available new, is this true. Anybody know.???
Just in case I find that to be the problem, I'll know I have to find used or get it through the after market. Nigel got his from Rock Auto based on his post.
Thanks Again, this has been a tremendous help already and I haven't even started on the car yet. But I'm hoping I can test the Boost Control Solenoid, find it bad, order one and replace with ease.
I Hope,
Rick

Rick I called my local Buick dealership and they checked their system and were able to find one for me. This was less than a month ago and I paid about 40 dollars for it plus the shipping charge from California. It helps if you make friendly with the parts guy or they often won't bother. I think I still have the number of the place that had it. Let me know if you want it and I'll dig it up for you.

Thanks Derek, I'll let you know. As soon as I'm done troubleshooting this car.
Probably be Monday or Tuesday before I get back to it.

Guys,

The boost by pass solenoid I use was a part specified for a Mitsubushi!. Its produced by AC Delco and the only difference was the mounting bracket, which can be swapped easily. I found this on an EVO forum and they recomend replacing thier original (OEM) with this part as "the BUICK" part was a better performer under load.

from Rock Auto ACDELCO 214474 (214-474) Turbocharger $ 52.89

i hope that is a little clearer.

Nigel

That's much clearer.
Good to know there is an alternative P/N from ACDelco.

hello ppl hope all is well!!Driving around today with my windows up and the ac on auto I threw a p0640 code. I parked the car ran my obd-1 reader and this code came up, shut down the ac and about 15 minutes later the light turned off.All suggestions welcome.stay healthy take care!!!Is the circuit hard to replace?Still trying to figure the cruise control out.i got my new FSM , learning as I go. can a tech 1 pinpoint the problem?

Rivieraz wrote:

hello ppl hope all is well!!Driving around today with my windows up and the ac on auto I threw a p0640 code. I  parked the car ran my obd-1 reader and this code came up, shut down the ac and about 15 minutes later the light turned off.All suggestions welcome.stay healthy take care!!!Is the circuit hard to replace?Still trying to figure the cruise control out.i got my new FSM , learning as I go.   can a tech 1 pinpoint the problem?

No such code for our cars.  Has to do with intake air heater circuit, which AFAIK, our cars don't have.  See if that code is even listed in the 95 FSM, it isn't in my 98.

https://www.obd-codes.com/p0640

it is not

took some time but it's fixed, it was the boost bypass valve. the beast is runnin like a top!!ZZperformance

Great sleuthing... please post more details...

well the only other thing to notice is when i took off the bypass valve acuator i put my finger over all the vacuum ports and pushed and pulled on the metal rod there was no resistance it moved freely up and down my mechanic said the internal valve was shot .also i had to put a elbow vacuum line on, the top vacuum port is on the side where the old vacuum port is on the very top of the bypass  acuator .I bought it at ZZPerformance m90 acuator 79.99

ok.  Good that you figured it out.  I have an actuator I pulled off a low mileage Park Ave but I am still waiting for my actuator to fail...