Code 61 with secondary system removed?

[scorp508]

What are the chances the value names themselves are slightly misleading? I don't have a commented/disassembled file to read. I'm working on creating one in spare time, which isn't much lately. . Just disassembling has been slow as I only have a few mins to work on it here and there and that doesn't work well.


According to the FSM, at least in '94...

<41 kPa triggers the electric vacuum pump to run provide more vac if the secondaries are commanded in FULL mode.

<21 kPa triggers DTC 61 in FULL mode.

Any vacuum in NORMAL mode triggers DTC 61. Would they use <101.4 kPa to define any vacuum.

With XFire's conversion we see two values eerily close to two known FSM conditions: (1) start the vac pump if under 41 kPa and (2) set DTC 61 if under 21 kPa.


What if min vac to open meant to start the vac pump and was not related to the secondaries themselves? Just throwing it out there.


A value close to <101.4 kPa somewhere else to define "any vacuum" to set the "any vacuum in normal mode set DTC 61" using XFire's conversion would still be a 1-byte value of 254 or 0xFE hex, while Todd's conversion would require a double-byte value coming in at 302.


On a wild assumption it would be stored near these values, it may not be, I don't see an 0xFE next to these two values in BMCB, but there is a 0xFA (250 dec, 102 kPa) and a 0xF0 (240 dec, 99 kPa) nearby. I don't see a double-byte 120E (302 dec) nearby or anything similar.


Thanks for letting me nerd out a bit.

-b

[tpepmeie]

Originally Posted by scorp508

What are the chances the value names themselves are slightly misleading? I don't have a commented/disassembled file to read. I'm working on creating one in spare time, which isn't much lately. . Just disassembling has been slow as I only have a few mins to work on it here and there and that doesn't work well.





According to the FSM, at least in '94...



&lt;41 kPa triggers the electric vacuum pump to run provide more vac if the secondaries are commanded in FULL mode.



&lt;21 kPa triggers DTC 61 in FULL mode.



Any vacuum in NORMAL mode triggers DTC 61. Would they use &lt;101.4 kPa to define any vacuum.



With XFire's conversion we see two values eerily close to two known FSM conditions: (1) start the vac pump if under 41 kPa and (2) set DTC 61 if under 21 kPa.





What if min vac to open meant to start the vac pump and was not related to the secondaries themselves? Just throwing it out there.





A value close to &lt;101.4 kPa somewhere else to define "any vacuum" to set the "any vacuum in normal mode set DTC 61" using XFire's conversion would still be a 1-byte value of 254 or 0xFE hex, while Todd's conversion would require a double-byte value coming in at 302.





On a wild assumption it would be stored near these values, it may not be, I don't see an 0xFE next to these two values in BMCB, but there is a 0xFA (250 dec, 102 kPa) and a 0xF0 (240 dec, 99 kPa) nearby. I don't see a double-byte 120E (302 dec) nearby or anything similar.





Thanks for letting me nerd out a bit.



-b

I will post the relevant code section a little later. I have another GM document in hard copy form at home, which I can double check the conversion. Not with me at the moment though.



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[XfireZ51]

I believe u are way ?overthinking? this. If ur objective is to keep the secondaries open in all conditions except idle and decel, then what was sent is what is working for many users. U will likely never see 10.41kPa unless perhaps ur on Mt. Everest or 104 unless ur using FI in which case u need a 2 or 3Bar MAP sensor.

[scorp508]

Originally Posted by XfireZ51

I believe u are way ?overthinking? this.

Oh I absolutely am, I love details to a fault! In addition to fixing things I love the learning opportunity of tearing things down to their most raw components.

If ur objective is to keep the secondaries open in all conditions except idle and decel, then what was sent is what is working for many users. U will likely never see 10.41kPa unless perhaps ur on Mt. Everest or 104 unless ur using FI in which case u need a 2 or 3Bar MAP sensor.

I was in the middle of writing a similar paragraph when you replied. If these values are only ever used to control if the secondaries should be allowed open/closed based on kPA, then 100% in agreement. I was going down a path in my head of whether or not these are also used to set DTC 61, but it seems unlikely, and those values are probably in another address.

[tpepmeie]

I said several posts back that the ?fix? was correct. Scorp seemed to have a desire to learn more so I was just sharing what I have.


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[scorp508]

Originally Posted by tpepmeie

I said several posts back that the ?fix? was correct. Scorp seemed to have a desire to learn more so I was just sharing what I have.

I appreciate it, Todd. You're correct I love to learn the ins and outs. With this community being limited in size I worry about the day folks start to disappear and want to suck up as much brain food as I can.

[tpepmeie]

Here is the relevant code, from BFXB. BMCB same, but addresses are different in that due to code changes:

LD55D	BRSET	DIAGMW3;BIT0,LD5CF	1=MALF 61 ACTIVE (VAC TOO HIGH TO CLOSE PRT THR)	
				
	LDAA	ADPTVAC	                 PORT THROTTLE ACTIVATION VACUUM	
	CMPA	KKVACCLS		MALF 61: MAX VAC ALLOWED TO CLS PRT THROTTLES
	BHI	LD56E		
	BCLR	DIAGMW3;BIT6	         1=MALF 61 ACTIVE (VAC TOO LOW TO OPEN PRT THR)	
	BRA	LD5D2		
				
LD56E	LDAA	M61TMR	        COUNTER FOR M61 (PORT THROTTLES)	
	CMPA	KKCNVPTM		MALF 61: MIN VAC PROBLEM TIME TO SET M61
	BHI	LD57B		
	INC	M61TMR	                COUNTER FOR M61 (PORT THROTTLES)	
	BRA	LD5D2		
				
LD57B	BRSET	DIAGMW2;BIT0,LD5D2	1=MALF 56 ACTIVE (PORT THROTTLE VACUUM SENSOR FAIL)	
				
	BSET	DIAGMW3;BIT0	            1=MALF 61 ACTIVE (VAC TOO HIGH TO CLOSE PRT THR)	
	BRA	LD5CF

[tpepmeie]

I have confirmed the correct conversion for that variable, by referencing another GM document.

ADPTVAC (kpa) = N * (1/2.70045) + (-28.764/2.70045)

simplified to

ADPTVAC (kpa) = N * .37031 - 10.6516

Thus the thresholds for Code 61 are:

85*.37031-10.6516 = 20.8kpa
38*.37031-10.6516 = 3.4kpa

[scorp508]

Originally Posted by tpepmeie

I have confirmed the correct conversion for that variable, by referencing another GM document.

ADPTVAC (kpa) = N * (1/2.70045) + (-28.764/2.70045)

simplified to

ADPTVAC (kpa) = N * .37031 - 10.6516

Thus the thresholds for Code 61 are:

85*.37031-10.6516 = 20.8kpa
38*.37031-10.6516 = 3.4kpa

Todd, nice work. I didn't look at the flow chart before, but that 3.4kPa does come into play for system diagnosis.

[scorp508]

Given the above it feels as if "Max Vac kPa to Close" maybe should be something like "Max secondary Vac kPa while port closed" as it appears to be testing the existence of any vacuum while the secondary air inlet solenoid valve is closed.


The troubleshooting flowchart of the value being >= 3.4 kPa leads you to either (a) Faulty solenoid or (b) Plugged/restricted solenoid valve vent or (c) Faulty ECM.

Using either conversion likely fools the ECM enough to work, given the secondary vacuum pump turns on at 41 kPa and off at 57 kPa.

Stock BMCB.

Max vac kPa to close: 24.44
Max vac kPa to close: 3.42 (GM formula per Todd)
Min vac kPa to open: 41.78
Min vac kPa to open: 20.82 (GM formula)

Suggested modification for secondaries deleted from earlier in the thread.

Max vac kPa to close: 104.51
Max vac kPa to close: 83.78 (GM formula)
Min vac kPa to open: 10.41
Min vac kPa to open: -10.65 (GM formula)


Trying to set 104.51 kPa with the GM formula would need more than 1-byte, so best you can do (short of code alteration) is 83.78 due to reaching FF(h), but GM didn't need more than 1-byte if they only needed 55(h) / 21 kPa to begin with. Still a value of 83.78 is likely high enough.

I'm going to try 0 kPa (to open) and 83 kPa (to close) and see if the code triggers again.