Intermittent Code 61 Ideas

[GOLDCYLON]

Hi there GC needs a little help. I getting an intermittent SES light that wont hard set but always leads back to a code 61 (Secondary port throttle system error). Would a bad or non working vacuum pump cause this issue? It happens the most of the time when the Cruise control is set and the car has to pickup speed in 6th gear. As the car has to accelerate the SES light will illuminate and when the car levels off in terrain the light goes away. Im reading the troubleshooting section of the FSM and it appears when the Vacuum secondary actuators lose pressure that the ECM commands the air pump to kick in to compensate.

From what im reading either one of these actuators are suspect, as is a check valve, Air pump, secondary port actuator and the tubing. Asking if anybody else outthere has seen this repeat symptom. Is there a check for just the vaccum pump. I dont know if it ever comes on as my fans race on almost immediately in my car due to the prom setting. Just looking for ideas and any been there's and done thats. out there Thanks Daryll :happy1:

[jonszr1]

darrell, 2 things have you tried having someone turn the ignition on but not to start with you out by the vac pump .if it working it should go on for a very short period and then shut off. and 2 you can override the prom setting by taking your valet key and turning it off. then go put it in cruize control on the freeway and see what happens that will narrow it down for you . oh yeah there is also a fuse for the vacpump on the inside of the drivers wheel well . ck the service manual just to be sure . the fuse was out on my 92 when i first got it .dont know why it blew but replaced it and never had another problem . hope this helps

[jonszr1]

also the corvette action center has a really good and quick troubleshooting guide in the zr1 section

[tomtom72]

Daryl, I know you don't want to hear this but an intermittent 61 usually is vacuum related....usually. Figure the control solenoid is an on - off switch, so electrically it has to set a hard code if that side of it fails. If the vacuum side has a soft failure, like crap in it, then the 61 becomes intermittent. Likewise if the pull off canisters have soft failure in the rubbers, then maybe an intermittent 61 happens. Oh, also the second MAP sensor under the ECM where the ECM monitors the level of vacuum during secondary operation...that could also be the source of a 61, or any of the vacuum hose connected to any of the stuff under the plenum for the secondary system....which then goes back to the pump & any issues it could have.

JMHO
Tom:o

:cheers:

[GOLDCYLON]

Tom there is a seconary MAP sensoner under the ECM? I had no idea I thought there was only one behind the plenum. Is that on the underside of the ECM bracket?

[GOLDCYLON]

I would much rather chase a vacuum connection/leak than an electrical connection/leak :thumbsup:

Agreed

[QB93Z]

GC, I am not sure if the Code 61 is related but here is what I observed on a 1994.

There is a pressure switch that monitors Secondary Vacuum and turns OFF the Secondaries if they have been commanded ON and the Secondary Vacuum drops too low to hold the secondaries open.

During acceleration, the Secondary system would cycle on and off. I had a scanner connected to the car during operation. What was happening was that a bad check valve between the secondaries and the other vacuum uses allowed vacuum "loss" when manifold air pressure went up (throttle valves wide open). The secondary vacuum pressure switch would sense rising pressure (loss of vacuum) and would shut off the secondaries. I believe that a code occurs from that event.

Jim

[bdw18_123]

Daryl, I know you don't want to hear this but an intermittent 61 usually is vacuum related....usually. Figure the control solenoid is an on - off switch, so electrically it has to set a hard code if that side of it fails. If the vacuum side has a soft failure, like crap in it, then the 61 becomes intermittent. Likewise if the pull off canisters have soft failure in the rubbers, then maybe an intermittent 61 happens. Oh, also the second MAP sensor under the ECM where the ECM monitors the level of vacuum during secondary operation...that could also be the source of a 61, or any of the vacuum hose connected to any of the stuff under the plenum for the secondary system....which then goes back to the pump & any issues it could have.

JMHO
Tom:o

:cheers:

So that's what that is. I saw that under the ECM on my '90 ZR-1, looks the same as the primary MAP sensor (minus the silver bracket). Was wondering why there was a second one. Good info, thanks Tom!


Tom there is a seconary MAP sensoner under the ECM? I had no idea I thought there was only one behind the plenum. Is that on the underside of the ECM bracket?

Here is a picture of the one on my Z:

http://i13.photobucket.com/albums/a292/bdw18_123/STA70076-1.jpg

[GOLDCYLON]

Jim I think that is certainly possible. I need to set aside the time to trouble shoot all these areas. I have a new Pump, one new silver metal actuator that works and a new Secondary throttle black plastic actuator. Now I know why a lot of folks are eliminating this system and pinning back the secondaries

[Pete]

When your on the throttle does it shut down at 3k?
If so check your power switch make sure it works/stays on.
Put a scanner on the car check the volts on secondary MAP it needs to be below 3.6 volts.
Otherwise you have a vacuum leak search and find leak,also check vacuum actuators put vacuum to them make sure they open by 7" of vacuum and stay open,they don't usually go bad but if your in there might as well check them.

Just a thought you sure you plugged in the electric plug to the vacuum solenoid. Done that once:)
Since then i yanked the secondaries.

Pete

[Paul Workman]

The casual reader of this and other ZR-1 boards quickly pick up on the fact that the 15-20 year old vacuum circuit is one if not THEE most common nags associated with the LT5s.

Parts not used don't cost anything and they seldom break!

http://i185.photobucket.com/albums/x220/6PPC_bucket/tech%20files/ZR-1009.jpg

I'm using Marc Haibeck's secondary elimination chip b/c it has several other drivability features really worth the $$: The fans come on early, the idle, especially on startup is handled nicely, fueling and spark advance minimize power loss when the engine is at normal op temp, and a couple more features too...Not to mention no more finicky secondary naggings! Eliminating the damn things is a consideration. And, there just might be a few more ponies in there when the throttle rods and plates are out of the air stream!

http://i185.photobucket.com/albums/x220/6PPC_bucket/tech%20files/ZR-1007.jpg

P.

[GOLDCYLON]

When your on the throttle does it shut down at 3k?
If so check your power switch make sure it works/stays on.
Put a scanner on the car check the volts on secondary MAP it needs to be below 3.6 volts.
Otherwise you have a vacuum leak search and find leak,also check vacuum actuators put vacuum to them make sure they open by 7" of vacuum and stay open,they don't usually go bad but if your in there might as well check them.

Just a thought you sure you plugged in the electric plug to the vacuum solenoid. Done that once:)
Since then i yanked the secondaries.

Pete

Hi Pete no it does not shutdown at 3K. My Power key is defeated at the Prom level so its always on. The pump works and I now have the answer to what that Brrrraaaaap sound is when I turn the key before I start the car. I thought that was a Battery ECM sound to be honest. I pulled the rubber hose to the pump and it immediately started pumping when I tried to block the tube next to the oil filter.

I checked the hose connection at both MAPs I am convinced one of the Metal vaccum actuators is toast and time for a plenum pull. Jim check valve is also a certain possibility. :dontknow:

[GOLDCYLON]

So that's what that is. I saw that under the ECM on my '90 ZR-1, looks the same as the primary MAP sensor (minus the silver bracket). Was wondering why there was a second one. Good info, thanks Tom!




Here is a picture of the one on my Z:

http://i13.photobucket.com/albums/a292/bdw18_123/STA70076-1.jpg


Great pic. I remembered that when I replaced my ECM holder about 6 months ago. I had no idea where that line went too until I traced it down. However dood... where the hell is your brake fluid lol?

[Pete]

If you need the vacuum actuators,i have 2 brand new actuators i will sell $250 for both.

Pete

[GOLDCYLON]

I'll keep that in mind thanks Pete

[Dynomite]

I checked the hose connection at both MAPs I am convinced one of the Metal vaccum actuators is toast and time for a plenum pull. Jim check valve is also a certain possibility. :dontknow:

When you say toast ......do you mean you think the bellows is leaking or the acutator is stuck and not working......or.....the vacuum line connection is leaking?

Do the secondary actuators look like they are functioning when you look down through the plenum?

I know you are aware of this but......
I checked the secondary actuators using a dull sewing needle alongside the pin C17 (pink with black stripe 1991) where it is connected to the ECM. I used a small aligator clipped electrical wire attached to the sewing needle. I turned on the ignition switch and then grounded the other end of the aligator clipped wire while looking straight down (each side) between middle two intakes using a flashlight. As you ground the end of the aligator cable you will see the vacuum actuator pull the secondary linkage ;)

Paul Workman......I am thinking of your suggestion eliminating the secondary actuator control system and having Marc program/reprogram my chips (yes I have a couple) :mrgreen:

In your last post in that thread http://www.zr1.net/forum/showthread.php?t=9370&page=8 was that idle issue taken care of....did you have Marc program the chip for secondary injectors on at idle? Are the secondary injectors programmed in sync with the primary injectors or how does that work?

It IS as simple as removing the secondary vacuum pump associated hardware, actuators, and even the throttle plates too!
P.

I assume you mean each throttle plate in each secondary and elimination of the shafts also using your shaft removal technique?

I would pull the shafts and plug the holes....Marc program the chip accordingly :thumbsup:

Did you eliminate the secondaries before or after porting and did the fact you eliminated the secondaries have any effect on how you ported the injector housing?

I just sent Marc an e-mail

Back to you GC :thumbsup:

Hi there GC needs a little help. I getting an intermittent SES light that wont hard set but always leads back to a code 61 (Secondary port throttle system error). Thanks Daryll :happy1:

[GOLDCYLON]

I think one or both of the metal actuators are leaking. Or the pump is not compensating for a low pressure demand in 6th gear. I suspect this is causing the intermittent Code 61

I have found all the charts in the FSM and will pull out the Tech 1A this weekend. Flying out of town again tomorrow but will be back soon. At least it appears it can be diagnoised to just before the point of a plenum pull. Hopefully its something simple.

[bdw18_123]

Great pic. I remembered that when I replaced my ECM holder about 6 months ago. I had no idea where that line went too until I traced it down. However dood... where the hell is your brake fluid lol?

:mrgreen: There is fluid in the reservoirs, it's just low. Was like that when I bought the car.

[Paul Workman]

Paul Workman......I am thinking of your suggestion eliminating the secondary actuator control system and having Marc program/reprogram my chips (yes I have a couple) :mrgreen:

In your last post in that thread http://www.zr1.net/forum/showthread.php?t=9370&page=8 was that idle issue taken care of....did you have Marc program the chip for secondary injectors on at idle? Are the secondary injectors programmed in sync with the primary injectors or how does that work?

No, I haven't latched the secondary relays; still controlled by the ECM. Neither I nor anyone with the secondaries removed has had an SES event (yet) that would shut down the secondary injectors. But, once I get the LT5 back in, it will be back on the radar as a "todo" this season.

I assume you mean each throttle plate in each secondary and elimination of the shafts also using your shaft removal technique?

Yep. Use the Dorman 555-108 freeze plug and a socket way smaller than the plug to drive the plug in place. (Thank Pete for that bit of info)

I would pull the shafts and plug the holes....Marc program the chip accordingly :thumbsup:

Did you eliminate the secondaries before or after porting and did the fact you eliminated the secondaries have any effect on how you ported the injector housing?

I pulled the secondary hardware after porting the top end, before semi-porting the heads (in place). The secondary ports on the heads are at 36mm (stock). The secondary plates would not necessarily have had to come out, but I did remove them for better air flow, and because I radiused (is that a word?) the transition between the IH and the head, somewhat, to soften the bend between IH and the head.

The primary side is another question: That too is 36mm at the IH outlet. So, the head is opened up quite a bit to mate with the IH. From what I gather, most simply go down into the head, maybe a half inch to blend. I was working in a phased approach: always intending to port the heads, at a later date (Phase-II). As an interim step, what I did was create a smooth transition from the input of the head all the way down to the valve guide; about 3-1/2". (Man! I do so wish in retrospect that I had dyno'ed the car before pulling the heads (to fix a valve issue). I'd bet a steak dinner the net result of the P&P with the taper in the heads was worth significantly north of the 30 or so hp gain that is typical for a P&P.)




As for the heads,

I just sent Marc an e-mail

Back to you GC :thumbsup:

:happy1:

>>

[tomtom72]

Good morning guys!:wave:

Yes, that MAP under the ECM bracket is what our ECM uses to monitor the state of vacuum during secondary operation. The vacuum hose attached to it originates at the T-ee fitting at the left actuator. Also, now I'm not 100% sure on this but I'll post it as a "beware" kind of thing.:o

The MAP under the ECM I think is a different part number. Not sure, but I remember doing something and trying the electrical connector on my spare MAP sensor from behind the plenum, and it seemed not to want to plug into the MAP's socket???? This is a big "not sure about this" on my part. I think I was just doing a let's see if this works thing, and I couldn't get the plug in my spare plenum mounted MAP.....I was kind of surprised, but I have never revisited this issue to nail it down:o I will this weekend if I have a chance, now that I'm thinking about it. I was doing my own diagnosis of a hard 61 about three years ago, and I brought all my spare parts with me to the garage I rent so as not to forget anything I might need. As usual, I was in a hurry to get the 61 cleared up as it was a week before my first Carlisle and I wanted to take the Z. My 61 was the ECM.

:cheers:
Tom

[XfireZ51]

GC,

Also possible to strap actuators open and then re-do calibration for secondaries
on at any point off idle. Also, use an electrical plug to feed the ECM a signal that deals with need for vacuum.

[Dynomite]

But, once I get the LT5 back in, it will be back on the radar as a "todo" this season.


Thanks Paul :thumbsup: .......your LT5 is not "in"?

Marc came right back to me on secondaries (Marc is extremely fast) :thumbsup: ......which reason #1 (which I am sure he doesn't mind me inserting here) is applicable here :mrgreen:
I would say that removing the secondaries is not a bad idea. A few years ago we dyno tested removing the secondary throttles and found nothing. There are three situations where removing the secondaries are useful. 1. If you are having a problem with them that you can't fix, they can be eliminated. 2. If you can't find a repair part. 3. If you have removed them to port the heads, you can save time and not reinstall them.

Removing them does not effect the idle, fuel economy or torque over 1500 rpm. I believe that they are an advantage for an emission test.


Good morning guys!
My 61 was the ECM.

Tom

Tom....at what point did you quit chasing vacuum leaks and switch ECMs? I assume when you switched ECMs in the diagnoses you moved your chip to the ECM you switched in ;)

Where did you pick up the second ECM? :happy1:

GC,
Also possible to strap actuators open and then re-do calibration for secondaries on at any point off idle. You are saying recalibrate the chip secondaries on at every point except at idle?
Also, use an electrical plug to feed the ECM a signal that deals with need for vacuum.
When I look at the engine Vacuum diagram I see MAP sensor, Fuel pressure regulator, PCV valve assembly, A/C vacuum tank, Differential pressure switch, Vapor canister control valve, and a line to brake servo. So there are lots of needs for vacuum :dontknow:

[tomtom72]

Hi Cliff.

At what point? Ya know.....:o...I'm doubly embarrassed because the hard 61 set while I was out with the car. I was doing a 2nd gear exit ramp / on ramp and the SES light popped up and instantly I was limited to 3k rpms....it was as if I had dropped an anchor!

Okay so I limp home, 25 miles and plug in my scanner. (I already knew the code number from my Gordon jumper kit that I keep in the car.) I even tried the clear code option and it resets in an instant, and the car is idling! I should have known right then that my issue was electrical. The speed of light? If it was a vacuum issue I would have had to wait for the code to reset. Sometimes I can be sooooo dumb!...well, most times actually.:sign10:

Anyway, vacuum differential sensor = MAP under the ECM bracket. I use the FSM chart and waste 1/2 a day running the DTC 61 diagnostic chart only to find that nothing is wrong except for the ECM. I swap ECM's and viola no 61.

I bought the ECM as a spare when I first got my car back in late 04 from a chevy dealer.

Sometimes I think God is trying to tell me that I should not own any corvette, let alone a ZR-1.:cry:

[scottfab]

......the fact that the 15-20 year old vacuum circuit is one if not THEE most common nags associated with the LT5s.
Parts not used don't cost anything and they seldom break!
P.

What does that do to resale? How do you keep your son or guest driver from using to much HP.
I think I'll keep mine the way it is, more for the guest driver :dancing
After all GM has all those expert engineers and they would not design it that way unless it was right............ well someone said that way back when.
I don't believe it. Just thought I'd throw that in.:dontknow:

[phrogs]

well since I don't have guest drivers Im removing my secondaries Im sick of the BS of dealing with them.

I have been getting a Code 61 at high RPMS and with a moded motor I don't feel that one more thing is going to hurt it at all.

Makes my plenum pull all the more enjoyable!

My spare 90 chip just went out in the mail about an hour ago to go to Mark.

[tomtom72]

I was just thinking about this "ditching the secondaries" thing. I mean no offense to anyone with MHO.
I think that any one interested enough to actually want to own a ZR-1 knows already about the advantages that not having all that crap under the plenum to mess with are real. The people that are totally outside our community will probably not even realize that the stuff isn't installed until they have to pull the plenum. I'm sorry but the people that are potential "casual" ZR-1 owners don't know enough about the LT5 before buying. They want a garage queen and since they are not going to drive the car that much, they'll never know!:p

And lastly, and the biggest BFO to me anyway....is that I just realized that my car has passed NYS smog Nazis inspection the last four years with the power key in the "FULL POWER" position! And the NYS test on OBDI cars is a chassis dyno load test thru a simulated city/highway loop. The numbers were not so good, but they were not over the limits! :icon_scra

[John Boothby]

I am looking for the secondary MAP sensor that is under the ECM. Anyone know the pn and if it is available from the dealer? If not, does anyone have one to sell?

Thanks.

ps: I replaced all secondary plumbing/actuators/solenoids and check valves under the plenum. All was fine for a few months, then an intermittent Service Engine Soon lite. I traced down using the red SM and Tech 1A to the solenoid under the front of the plenum. I replaced that, but soon after got another code 61. Now I think it might be the sensor under the ECM. By the way, the lite only comes on when all the parameters for the secondaries are good and I step on it. What about the MAP sensor behind the plenum? I don't show any leaks. ie using a vac gauge and the actuators work when hooked to a hand vac pump.

[tomtom72]

John, I just used my parts CD to look up the GM P/N's for the two MAP sensors, and then searched at GM Parts Direct and came up NLA on both.

The two MAP's have different P/N's on my parts CD.

I'm going to say that this is going to require research that I'm not sure how to do.:o


RockAuto.com says that the ACDelco P/N is 16231141 for the intake manifold differential sensor. I just don't know which MAP that they are talking about.

sorry:redface:

Tom

[John Boothby]

Thanks for the effort. I guess I'll have to make some phone calls. I am not sure that these are the problem, but since I redid all the secondary vac plumbing I might as well replace the MAP's also. That is if I can find them.

[XfireZ51]

I am looking for the secondary MAP sensor that is under the ECM. Anyone know the pn and if it is available from the dealer? If not, does anyone have one to sell?

Thanks.

ps: I replaced all secondary plumbing/actuators/solenoids and check valves under the plenum. All was fine for a few months, then an intermittent Service Engine Soon lite. I traced down using the red SM and Tech 1A to the solenoid under the front of the plenum. I replaced that, but soon after got another code 61. Now I think it might be the sensor under the ECM. By the way, the lite only comes on when all the parameters for the secondaries are good and I step on it. What about the MAP sensor behind the plenum? I don't show any leaks. ie using a vac gauge and the actuators work when hooked to a hand vac pump.

John,

Before replacing the Diff MAP sensor, any chance you could put a Mity Vac on it and scantool. By applying suction, you could read if sensor is reacting correctly. The Lean O2 condition is obviously due to secondary injectors not coming on when the threshold TPS x RPM is reached so params for secondaries are not being met. Are secondaries holding vacuum with Key On? I had a similar thing happen a couple of years ago and it turned out to be fuel pump. The sock filter was pretty filthy

[John Boothby]

By scantool are you refering to a Tech 1? I do have one with correct ECM cartridge. The system is holding vacumn. The pump comes on for a few seconds when the key is turned on and then shuts off and stays off.

[XfireZ51]

By scantool are you refering to a Tech 1? I do have one with correct ECM cartridge. The system is holding vacumn. The pump comes on for a few seconds when the key is turned on and then shuts off and stays off.


I wouldn't mind having a Tech 1 myself. Yes, it's a scantool. When you go Key On and secondary pump cycles, what is the reading for the Diff MAP sensor voltage? If the pump is shutting down, that tells me sensor is reading correctly and signaling ECM that there is sufficient vacuum to run secondaries. That would lead me to think it's not MAP sensor. If secondaries were not operable you would get a code 55? I think as well. If just getting code 61, then it's a Lean O2 condition which is shutting down the secondaries. So the issue is why is A/F going lean.

[FULLPWR]

Hey John,
I just replaced both on my 90 with ACDELCO's,

under the ECM
the acdelco box it came in states the same no. for ac/gm
ACD# 16232241
GM# 16232241


MAP SENSOR back of plenum
ACD# 213-1545
GM# 12569240

:cheers:

Luis

[Dynomite]

Daryl, I know you don't want to hear this but an intermittent 61 usually is vacuum related....usually. Figure the control solenoid is an on - off switch, so electrically it has to set a hard code if that side of it fails. If the vacuum side has a soft failure, like crap in it, then the 61 becomes intermittent. Likewise if the pull off canisters have soft failure in the rubbers, then maybe an intermittent 61 happens. Oh, also the second MAP sensor under the ECM where the ECM monitors the level of vacuum during secondary operation...that could also be the source of a 61, or any of the vacuum hose connected to any of the stuff under the plenum for the secondary system....which then goes back to the pump & any issues it could have.
JMHO
Tom

So that's what that is. I saw that under the ECM on my '90 ZR-1, looks the same as the primary MAP sensor (minus the silver bracket). Was wondering why there was a second one. Good info, thanks Tom!

Here is a picture of the one on my Z:

http://i13.photobucket.com/albums/a292/bdw18_123/STA70076-1.jpg

Hey John, I just replaced both on my 90 with ACDELCO's, under the ECM the acdelco box it came in states the same no. for ac/gm
ACD# 16232241
GM# 16232241

MAP SENSOR back of plenum
ACD# 213-1545
GM# 12569240

LuisJust putting all this together :wink:

[John Boothby]

Thanks bro's!!:cheers:

[GOLDCYLON]

I want to close this post out. I had broken #5 secondary port throttle valve shaft. It was broken in two at the center screw point. Must have been a factory fatigue flaw. Or maybe I hammer the secondaries too hard :dontknow:

Thanks to the ZFDoc for getting me back on the road and to Andrew for supplying with the secondary parts. Next go around the entire secondary system is coming out ;)

[GOLDCYLON]

I assume no broken parts were sucked into the cylinder :neutral:
Sounds like you already started to remove your secondary with another option on how to remove secondary valve shafts :D

Luckily no the parts were just floating around :censored: