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#31 |
![]() Join Date: Jan 2024
Location: Boston, MA
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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.
![]() 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 Last edited by scorp508; 06-06-2024 at 12:08 PM. |
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#32 | |
Join Date: Aug 2005
Location: Fishers, IN
Posts: 809
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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. Sent from my iPhone using ZR-1 Net Registry
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#33 |
Join Date: May 2007
Location: Chicagoland, IL
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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.
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#34 | |
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Oh I absolutely am, I love details to a fault!
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#35 |
Join Date: Aug 2005
Location: Fishers, IN
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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.
Sent from my iPhone using ZR-1 Net Registry
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#36 |
![]() Join Date: Jan 2024
Location: Boston, MA
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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.
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#37 |
Join Date: Aug 2005
Location: Fishers, IN
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Here is the relevant code, from BFXB. BMCB same, but addresses are different in that due to code changes:
Code:
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
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#38 |
Join Date: Aug 2005
Location: Fishers, IN
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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
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#39 | |
![]() Join Date: Jan 2024
Location: Boston, MA
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#40 |
![]() Join Date: Jan 2024
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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.
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1987: Z51 Coupe, Z51, 4+3, Yellow / Graphite 1994: ZR-1 #150, Admiral Blue / Black 2015: Z06 Coupe, Z07, M7, Arctic White / Red Last edited by scorp508; 06-10-2024 at 05:39 PM. |
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