C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Closed Loop

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Old May 17, 2008 | 06:27 PM
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Default Closed Loop

Any way to tell if Im in closed loop without a scan tool?

Thanks
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Old May 17, 2008 | 06:40 PM
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I can tell by the sound and the idle speed. What is your concern?
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Old May 17, 2008 | 06:42 PM
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Originally Posted by jsup
Any way to tell if Im in closed loop without a scan tool?

Thanks
Use a paper clip to jumper a and b on the diagnostic link.
The check engine light will flash quickly in open loop, then switch on and off evenly when in closed loop.
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Old May 17, 2008 | 07:14 PM
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Originally Posted by Pete K
Use a paper clip to jumper a and b on the diagnostic link.
The check engine light will flash quickly in open loop, then switch on and off evenly when in closed loop.
Jump while the car is running?
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Old May 17, 2008 | 07:16 PM
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Originally Posted by pkazsr
I can tell by the sound and the idle speed. What is your concern?
I put in a heated 02 sensor. When 65Z01 ran a scan we were not getting activity from the O2 sensor and the voltage was .04V, not the .8-.9 we would expect to see. Plus there was no other O2 activity.

So I said fk it. I put the stock one back in the collector and I want to see if I'm going into closed loop.

I ordered the cable to interface to the ECM. I have also downloaded Datamaster which gives 20 free records.

However, I don't have that stuff yet and I wanted to see if the car is going into closed loop today.
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Old May 17, 2008 | 07:21 PM
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Put the ECM into field service mode and watch the SES flases:
-jumper ALD A&B (upper right) with a paperclip
-start the engine and wait a copla mintues
-the SES flash rate will drop from 2Hz to 1Hz when it enters closed loop mode; this takes a set time, coolant temp high enough and the O2 sensor working
-the On & Off duration will tell if it's running rich or lean
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Old May 17, 2008 | 07:41 PM
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65Z01,
Isn't that pretty much exactly what Pete K said? And how do you tell if it is running rich or lean by the SES flashes?
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Old May 17, 2008 | 07:55 PM
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Yea, I just wanted to step by step thing to be sure the ign. is off before inserting the paper clip.

The SES On duration indicates Rich condition; the Off duration indicates Lean condition. So 1Hz flashes of equal duration measn she's closed loop at stoch A/F ratio.

This test info is from Ben Watson's book on Chevy FI, ISBN 0-7603-0422-X.
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Old May 17, 2008 | 08:02 PM
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Thanks guys

Rain is holding up, I'll try it.
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Old May 17, 2008 | 08:21 PM
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When you return from the test drive check the SES flashes at idle and then raise it to say 2k RPM hold steady and check again.
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Old May 18, 2008 | 10:48 AM
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After my H/C swap I put in headers with heated O2s. Datamaster showed only one side was working properly. I checked all the wiring and connections and couldnt seem to get the one O2 to read as fast as the good one. I put in a 1 wire O.E O2 on the side that wasnt working properly. Bingo! It only takes one side to trigger Closed loop. In theory since the O2 signals go back to the ecm, it should only take one to activate closed loop. FYI
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Old May 18, 2008 | 04:00 PM
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Originally Posted by bobmic93
After my H/C swap I put in headers with heated O2s. Datamaster showed only one side was working properly. I checked all the wiring and connections and couldnt seem to get the one O2 to read as fast as the good one. I put in a 1 wire O.E O2 on the side that wasnt working properly. Bingo! It only takes one side to trigger Closed loop. In theory since the O2 signals go back to the ecm, it should only take one to activate closed loop. FYI
I did the same exact thing. I put in the original 1 wire non heated, bang closed loop.
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