Code 61 during colder outside temp

[Wigert]

I get a code 61 (secondary*port*throttle*system*inoperative) during My morning driver to work but on the way home everything works fine. The temperatur difference has been around 15-20 degrees. This has occured everyday several days in a row. I have found a lot of information in the service manual but wanted to ask you guys if you have any experience that could point in any special direction regarding the different parts of the secondary system that could be the problem in this specific case.

Thanks!

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[XfireZ51]

Intermittent short somewhere or in a component.

[Wigert]

Originally Posted by XfireZ51

Intermittent short somewhere or in a component.

Hey

Thanks for the reply. So you think it is an electrical problem rather than a problem with the vacuum system parts? I thought maybe the colder temperatur would cause a leak in the system due to something shrinking, but thats is just my speculation... The code 61 appears while cruising in the highway after 5 min of driving in the morning. Very weird...

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[S.hafsmo]

From the other forum,

When DTC Code 61 sets, engine rpm is limited to 3K.

A vacuum sensor located under the plenum monitors how much vacuum is applied to the secondary actuators. By monitoring the Vacuum Sensor voltage output, the ECM knows how much vacuum is present.

During Full Power Mode when the secondary solenoid opens, the Secondary vacuum pump turns on at around 41 kPa/ 12hg to supplement engine vacuum. DTC61 will set if the vacuum drops below 21kPa.

During Normal engine power operation DTC 61 will set if any vacuum is present at the secondary valve actuators.

DTC 61 will set
Secondary air inlet valves are commanded closed (Secondary Solenoid closed) and vacuum sensor signal is between .74volts and 4.89 volts.

Secondary air inlet valves are commanded open (Secondary solenoid open) and vacuum sensor signal is less than 1.7 volts.

ECM monitors the secondary valve actuator sensor on the ECM Red connector Pin 12 a Gray/Black wire.

https://www.corvetteforum.com/forums...my-94-zr1.html


You mention this occurs while cruizing? As while the secondaries are not engaged? Could it be that the solenoid (which applies vacuum to secondary actuators) is leaking? Partially stuck open?
If it's the sensor, one might be able to disconnect the vacuum line to the sensor, and drive without activating the secondary system. I'd assume if the sensor is giving an intermittent false vacuum reading, it would give the code in spite of being disconnected.
If there is actual vacuum at the sensor, it should be possible to measure it at the hose end.


There are also multiple topics here on the .Net registery on this problem, just try this Google search link: https://www.google.com/search?q=%22C...:ZR1.net/forum

[32valvesftw]

The code appears after 5 mins on the highway in the morning? Heres what I think, when one first starts the car it runs in closed loop mode and does not utilize the inputs from all the sensors. when the coolant gets up to temp the engine runs in open loop and takes input from all the sensors. So I don't think its really temperature causing the issue, its just allowing the computer to show it you.
Im no expert on the secondary systems on these cars, so I can only suggest pulling the plenum and checking things.

[XfireZ51]

Originally Posted by 32valvesftw

The code appears after 5 mins on the highway in the morning? Heres what I think, when one first starts the car it runs in closed loop mode and does not utilize the inputs from all the sensors. when the coolant gets up to temp the engine runs in open loop and takes input from all the sensors. So I don't think its really temperature causing the issue, its just allowing the computer to show it you.
Im no expert on the secondary systems on these cars, so I can only suggest pulling the plenum and checking things.

Actually, its just the opposite. motor is running Open Loop when it first starts then goes to Closed Loop when it reaches operating temps. My point was that perhaps cold temps might be exposing an intermittent short which “disappears” with higher temps.

[Paul Workman]

Dom, It does sound "electrical". But, like the open vs. closed loop I think you're "180 OUT" (old electronics term means 'backwards') on the short vs. open (circuit). (SHORTS = something is gonna get HOT and burn...or melt a fuse @ the very least. OPENS = NO current flowing, e.g., a light switch, resulting in NOTHING is getting HOT.)

OP: Expansion and contraction with the changes in temp is more likely (I think) to cause an open when very cold, and reconnect when the metal expands with the rising temp. (Shorts vs. Opens: Shorts = high current and something will get HOT. Opens too can result in no voltage, but NO current. Nothing gets hot. (Just sayin!).

Starting with the vacuum pump (under the right headlight), is it working when very cold?

My approach would be to verify the vacuum circuit is sound and functional (See Marc Haibeck's site for his articles - one on vacuum leaks, but specifically on how to activate the secondaries while observing the actuators viewed from outside of the motor (i.e., w/o pulling the plenum).

Then verify the connector to the vacuum solenoid switch (under the plenum) is in good condition and the connection to the secondaries MAP sensor is also in good condition. (Note: the secondaries MAP sensor is attached under the ECM on a 90, but under the plenum on 91+

Course there IS a final solution to the whole vacuum and secondaries issue... (Do I have to say it??).

[XfireZ51]

Thank u Paul for “illuminating” me. Yes I was thinking open circuit.

[Paul Workman]

Originally Posted by XfireZ51

Thank u Paul for “illuminating” me. Yes I was thinking open circuit.

No prob!

[Wigert]

Yes it occurs after a couple of minutes while driving steady om the highway. I will have to find a vaccum pump to see if I have a leak.

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