ecm upgrade nightmare
Thread Starter
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
ecm upgrade nightmare
As some of you may remember I have done the ecm upgrade on my '85. I have been fighting small issues ever since doing it because of wire color mistakes in my fsm. I have most of them figured out but there are a few that just won't allow me to find them. To avoid confusion I am only going to ask about one at a time. When I use the stock memcal by itself the cooling fan does not come on until the ecm triggered it. When I put the piggyback in with the custom tune on it the fan comes on as soon as I fire the engine. Can anybody tell me what can be done to fix this? It did not do this at first but I have been tracing & moving wires so I have something in the wrong place.
Thread Starter
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
I upped to the 165 ecm and yes there are gobs of repin instructions out there but none of those instructions cover wire colors that are not what the FSM says they are supposed to be. I verified my harness with one at Vette2Vette and both of them were identical but not what the fsm calls for. I have a gray wire that is supposed to be green/white, I have at least 3 others that are not according to fsm. Add to that the fact there is more than one of many colors just in the ecm wiring alone then add the fact that when it comes to wiring I am not the sharpest saw in the shed and you have the makings for a futch up.
Le Mans Master
Joined: Feb 2005
Posts: 6,481
Likes: 566
From: Clearwater Florida
As some of you may remember I have done the ecm upgrade on my '85. I have been fighting small issues ever since doing it because of wire color mistakes in my fsm. I have most of them figured out but there are a few that just won't allow me to find them. To avoid confusion I am only going to ask about one at a time. When I use the stock memcal by itself the cooling fan does not come on until the ecm triggered it. When I put the piggyback in with the custom tune on it the fan comes on as soon as I fire the engine. Can anybody tell me what can be done to fix this? It did not do this at first but I have been tracing & moving wires so I have something in the wrong place.
Melting Slicks
Joined: Aug 2003
Posts: 3,401
Likes: 396
From: Lakeville MI
The converted 85 Corvettes that I have dealt with have required that the N.0. Cooling fan Req input flag be set to allow normal fan operation due to AC high pressure switch input. See Bit 5 below.
Just like with f-bodies, the switches seem to vary (with some being N.0. and others N.C.) in certain year cars. 85 Corvettes seem to be N.0. so they need to flag to be set, unlike 86-89 Corvettes which typically need the flag to be cleared.
Check this setting in your bins first and invert if necessary.
Don't know what mask or bin you are using as a base. Here is an example from a typical $32B bin.
LC017: FCB $08 ; 0000 0000 4th AIR FUEL MODE WORD
; Bit 0 = Use LV8 for BLM not dispflow
; 1 = not used
; 2 = 4th Gear Hwy Mode Spark Adv check enabled
; 3 = If CCP Chg, force Int to 128
;
; 4 = TCC locked Hwy Mode Spark Check enable
; 5 = N.O. Cooling Fan Req input
; 6 = Pwr Steer Pressure Sw installed
; 7 = Use TCC out to Cnt'l A/C Clutch
Just like with f-bodies, the switches seem to vary (with some being N.0. and others N.C.) in certain year cars. 85 Corvettes seem to be N.0. so they need to flag to be set, unlike 86-89 Corvettes which typically need the flag to be cleared.
Check this setting in your bins first and invert if necessary.
Don't know what mask or bin you are using as a base. Here is an example from a typical $32B bin.
LC017: FCB $08 ; 0000 0000 4th AIR FUEL MODE WORD
; Bit 0 = Use LV8 for BLM not dispflow
; 1 = not used
; 2 = 4th Gear Hwy Mode Spark Adv check enabled
; 3 = If CCP Chg, force Int to 128
;
; 4 = TCC locked Hwy Mode Spark Check enable
; 5 = N.O. Cooling Fan Req input
; 6 = Pwr Steer Pressure Sw installed
; 7 = Use TCC out to Cnt'l A/C Clutch
Thread Starter
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
The converted 85 Corvettes that I have dealt with have required that the N.0. Cooling fan Req input flag be set to allow normal fan operation due to AC high pressure switch input. See Bit 5 below.
Just like with f-bodies, the switches seem to vary (with some being N.0. and others N.C.) in certain year cars. 85 Corvettes seem to be N.0. so they need to flag to be set, unlike 86-89 Corvettes which typically need the flag to be cleared.
Check this setting in your bins first and invert if necessary.
Don't know what mask or bin you are using as a base. Here is an example from a typical $32B bin.
LC017: FCB $08 ; 0000 0000 4th AIR FUEL MODE WORD
; Bit 0 = Use LV8 for BLM not dispflow
; 1 = not used
; 2 = 4th Gear Hwy Mode Spark Adv check enabled
; 3 = If CCP Chg, force Int to 128
;
; 4 = TCC locked Hwy Mode Spark Check enable
; 5 = N.O. Cooling Fan Req input
; 6 = Pwr Steer Pressure Sw installed
; 7 = Use TCC out to Cnt'l A/C Clutch
Just like with f-bodies, the switches seem to vary (with some being N.0. and others N.C.) in certain year cars. 85 Corvettes seem to be N.0. so they need to flag to be set, unlike 86-89 Corvettes which typically need the flag to be cleared.
Check this setting in your bins first and invert if necessary.
Don't know what mask or bin you are using as a base. Here is an example from a typical $32B bin.
LC017: FCB $08 ; 0000 0000 4th AIR FUEL MODE WORD
; Bit 0 = Use LV8 for BLM not dispflow
; 1 = not used
; 2 = 4th Gear Hwy Mode Spark Adv check enabled
; 3 = If CCP Chg, force Int to 128
;
; 4 = TCC locked Hwy Mode Spark Check enable
; 5 = N.O. Cooling Fan Req input
; 6 = Pwr Steer Pressure Sw installed
; 7 = Use TCC out to Cnt'l A/C Clutch
I will pass this on though and hope for the best.The biggest thing is that this tune that I have did not do this when I first got it so there again, it almost has to be something I have done.
Thanks so much for the info, both of you.
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
I have a chip that did that. I removed it and installed one out of an 87 corvette. Don't know if anything is better, but the engine runs fine the way I have it .
I think it is a PCM chips for less. I don't have it handy right now, but it didn't work with the stock wiring without any changes at all. Remember the stock 86 chip you borrowed? stick it back in and see what happens.
I think it is a PCM chips for less. I don't have it handy right now, but it didn't work with the stock wiring without any changes at all. Remember the stock 86 chip you borrowed? stick it back in and see what happens.
Last edited by coupeguy2001; Jun 9, 2013 at 09:41 PM.
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Melting Slicks
Joined: Aug 2003
Posts: 3,401
Likes: 396
From: Lakeville MI
Attempt to clarify my previous post:
Pin D11 is the A/C high pressure switch input to the 165 ecm. The physical switch is either Normally Open (N.O.), or Normally Closed (N.C.) when the AC system is at low pressure.
The flag/switch setting in the bin must match the switch that's in the car.
86-89 Corvettes typically have a Normally Closed switch, so bit 5 should be unchecked (or set to 0) in the bin.
85 Corvettes and some F-bodies, instead have a Normally Open switch, so bit 5 should be checked (or set to 1) in the bin.
I'm assuming that your 85 has a normally open AC high pressure switch, and your bin is expecting a normally closed AC high pressure switch.
Check pin D11 continuity to ground to determine if the switch is either open or closed (and grounded) in its natural state.
If it is open and properly wired (connected to the AC high pressure switch), you will need to set bit 5 in your bin to correct.
As a simple test without making programming changes, you can ground pin D11 to see if the fan will behave as expected (this will simulate a normally closed switch configuration which we assume will match your current bin setting).
If you are working with a tuner that provided your custom tune, they should understand what to do. If you're tuning yourself, hopefully this is clear enough.
Pin D11 is the A/C high pressure switch input to the 165 ecm. The physical switch is either Normally Open (N.O.), or Normally Closed (N.C.) when the AC system is at low pressure.
The flag/switch setting in the bin must match the switch that's in the car.
86-89 Corvettes typically have a Normally Closed switch, so bit 5 should be unchecked (or set to 0) in the bin.
85 Corvettes and some F-bodies, instead have a Normally Open switch, so bit 5 should be checked (or set to 1) in the bin.
I'm assuming that your 85 has a normally open AC high pressure switch, and your bin is expecting a normally closed AC high pressure switch.
Check pin D11 continuity to ground to determine if the switch is either open or closed (and grounded) in its natural state.
If it is open and properly wired (connected to the AC high pressure switch), you will need to set bit 5 in your bin to correct.
As a simple test without making programming changes, you can ground pin D11 to see if the fan will behave as expected (this will simulate a normally closed switch configuration which we assume will match your current bin setting).
If you are working with a tuner that provided your custom tune, they should understand what to do. If you're tuning yourself, hopefully this is clear enough.
Thread Starter
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
I have a chip that did that. I removed it and installed one out of an 87 corvette. Don't know if anything is better, but the engine runs fine the way I have it .
I think it is a PCM chips for less. I don't have it handy right now, but it didn't work with the stock wiring without any changes at all. Remember the stock 86 chip you borrowed? stick it back in and see what happens.
I think it is a PCM chips for less. I don't have it handy right now, but it didn't work with the stock wiring without any changes at all. Remember the stock 86 chip you borrowed? stick it back in and see what happens.
Attempt to clarify my previous post:
Pin D11 is the A/C high pressure switch input to the 165 ecm. The physical switch is either Normally Open (N.O.), or Normally Closed (N.C.) when the AC system is at low pressure.
The flag/switch setting in the bin must match the switch that's in the car.
86-89 Corvettes typically have a Normally Closed switch, so bit 5 should be unchecked (or set to 0) in the bin.
85 Corvettes and some F-bodies, instead have a Normally Open switch, so bit 5 should be checked (or set to 1) in the bin.
I'm assuming that your 85 has a normally open AC high pressure switch, and your bin is expecting a normally closed AC high pressure switch.
Check pin D11 continuity to ground to determine if the switch is either open or closed (and grounded) in its natural state.
If it is open and properly wired (connected to the AC high pressure switch), you will need to set bit 5 in your bin to correct.
As a simple test without making programming changes, you can ground pin D11 to see if the fan will behave as expected (this will simulate a normally closed switch configuration which we assume will match your current bin setting).
If you are working with a tuner that provided your custom tune, they should understand what to do. If you're tuning yourself, hopefully this is clear enough.
Pin D11 is the A/C high pressure switch input to the 165 ecm. The physical switch is either Normally Open (N.O.), or Normally Closed (N.C.) when the AC system is at low pressure.
The flag/switch setting in the bin must match the switch that's in the car.
86-89 Corvettes typically have a Normally Closed switch, so bit 5 should be unchecked (or set to 0) in the bin.
85 Corvettes and some F-bodies, instead have a Normally Open switch, so bit 5 should be checked (or set to 1) in the bin.
I'm assuming that your 85 has a normally open AC high pressure switch, and your bin is expecting a normally closed AC high pressure switch.
Check pin D11 continuity to ground to determine if the switch is either open or closed (and grounded) in its natural state.
If it is open and properly wired (connected to the AC high pressure switch), you will need to set bit 5 in your bin to correct.
As a simple test without making programming changes, you can ground pin D11 to see if the fan will behave as expected (this will simulate a normally closed switch configuration which we assume will match your current bin setting).
If you are working with a tuner that provided your custom tune, they should understand what to do. If you're tuning yourself, hopefully this is clear enough.
Thread Starter
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
A BIG thank you to tequilaboy and coupeguy2001 for your answers, you were both right. I did have two wires switched and one of them is gray but the fsm insists it is green/white. Anyway, I straightened those out and the fan shut off, the rich idle went away and the car runs like it should now. Then I decided to pop the custom tune in, the fan came on and the stumble/hesitation was back. So tequilaboy pointed me in the direction of what wires were amiss and coupeguy revealed he had a chip that does the same thing mine does. Anybody want to buy a worthless, custom tune?