ccm/bcm testing

[aafc]

I have no speed, no mileage (odd) no instant or avg mileage. tbl codes are
32,34,36,38. clear codes still not working. sys lite flashes at times. car starts
runs ( ran 7.72@92 mph at points race this past weekend 1/8 mile track.
I'am using a tech 2 , check veh speed no reading on tech 2. per fsm 1990
section 8D pg 36 ? possible replace ccm/bcm. or can it be tested to see
if it is ok? car has an auto (4l80E) so i can see mph on the transmission control unit.
thanks
john
1990 white/black #2546
one of a few auto 4l80E eq zr-1's

[-=Jeff=-]

I wonder if the speed sensor is not working. Sys light flashing could be no communication with ccm/ecm

[WVZR-1]

Do you have anything in the speedo/odo LCD? If yes do your CCM checks from the DIC and see if it confirms them. I'd think yes. Everything pretty much addresses shorts to ground or an open circuit in the CCM.

The DIC diagnostics routine is here:

http://tech.corvettecentral.com/2011...trouble-codes/

Connector issue? Has the cluster been removed recently?

I'm guessing since the 4L80E has been there for a while that they did function at one time or another. Yes? To get the speedo/odo display operating originally I'd guess they needed to use a DRA to establish the signal OR there are tail-shaft housings that have been modified to use the mechanical gear drive/driven VSS. Which is used in your car? The 4L80E never had a mechanical drive/driven arrangement.

That's where I'd start - whatever was done to get the signal from the 4L80E to the CCM.

[aafc]

update,

checked VSS wiring up to the ECM yellow plug pin 5 connectivity from the
toss signal . The toss signal is a reproduction of VSS signal to use for ECM.
The VSS is used by the trans controller for controlling the trans.
Now about 2 months ago i had SYS flashing on the speed/odd display. Checked the codes for the CCM , codes H32- H34-H36 and H38. Cleared codes they did not return.This time the codes remained. Turns out that i found the ground wire
for ratio adapter to be loose causing the loss of MPH ODD, trip mileage etc.
remade ground connection will test later, 98% sure that is my trouble.
so no ground to the ratio adapter, no sig to ecm.
Thanks for the help
John
1990 white/black #2546
one of a few auto 4l80E eq. zr-1's

[Schrade]

Following this thread here John - I got one odometer digit with 'shaky' display - the '3X,000' digit (and put in the 4L60e).

...
ground wire for ratio adapter to be loose
...

Is this an added-in ground?


And this part I'm lost on too here...

so no ground to the ratio adapter, no sig to ecm.

My 90 FSM shows same schematic for Mod 1 CCM diags for 32, 34, 36, 38, and all involved circuits carry straight from CCM to IC display...

[aafc]

OK last update,
Just came back from test drive everything is working. Speed/ood instant mile
per gal, avg mile per gal, trip reading.
back ground
car 1990 zr-1 with 4l80E transmission using compushift transmission controller.
the compushift controller uses a signal call TOSS (transmission output speed
signal). this signal can be used to send inputs to your ecm. Now i use a
transmission raito adapter to sent toss sig to the ecm, but it goes first to
raito adapter.The unit has ground,+12v , sig in from toss and sig out to the ecm. Well they don't work very well when you lose ground connection. therefore
no ground no sig to the ecm from the raito adapter.
In an early post i said that about 2 months ago sys lite was flashing, but i
did not lose my speed/ood etc. when pulled the codes from the ccm/bcm
they were h32,h34,h36, and h38. cleared codes and they did not come
back. But with the ground being loose (all the time i lost my sig).
Repaired loose ground connection now everything works.
I have been working on an auto trans install since Aug.2004. since then
i have broke 2 4l60E's and 1 700r4 too much HP.
so i installed an 4l80E out of a 3/4 ton chevy truck. had it rebuilt with
2:75 1st gear 1:57 2nd gear 1:1 3rd gear 4th gear .75. rear end gears are
3.73. @ 70mph i can get 20mpg in cruse mode. around town 15-17 mpg.
At the track best run 11.58@120mph and during hot weather i run 11.70 to
11.88 @ 117 mph.
So it was the VSS sig in a way, signal was good but the ratio adapter did not see it.
hope i made this clear to everyone who helped me with things to look at.
thanks
John
1990 white/black #2546
one of a few 4l80E eq ZR-1's

[emmvette]

I had the same issue with the ground by the stereo this week. Same no display results, no function of the trip/reset buttons etc.

[Schrade]

You have the same wired-in radio adapter ground, that aafc has???







Or is yours, emmvette, a factory harness ground? Is it in the schematic above?

[aafc]

When i installed the auto trans in my car i used an after market electronic
ratio adapter between the vehicle speed sensor and ecm. the unit has 4 wires
black to ground red to +12v white output from vss and blue input to
ecm.(see FSM section 8A-33-0). The yellow wire is cut and the ratio adapter
wired in place. This unit was install back in Aug. 2004 when i started the auto
install. NOTE! only the yellow is connected to the ratio adapater per cust
help desk.Also the vss is called TOSS (transmission output speed sensor)
from the compushift wiring harness. so i'am not using the permanent magnet
generator shown in the FSM sec 8A-33-0.
hope this info helps.
John
1990 white/black 2546
one of a few auto 4l80E eq ZR-1's

[Schrade]

Originally Posted by aafc

When i installed the auto trans in my car i used an after market electronic
ratio adapter between the vehicle speed sensor and ecm. the unit has 4 wires
black to ground red to +12v white output from vss and blue input to
ecm.(see FSM section 8A-33-0). The yellow wire is cut and the ratio adapter
wired in place. This unit was install back in Aug. 2004 when i started the auto
install. NOTE! only the yellow is connected to the ratio adapater per cust
help desk.Also the vss is called TOSS (transmission output speed sensor)
from the compushift wiring harness. so i'am not using the permanent magnet
generator shown in the FSM sec 8A-33-0.
hope this info helps.
John
1990 white/black 2546
one of a few auto 4l80E eq ZR-1's

My bad there John; I mistook 'raito' adapter for 'radio' adapter; not gearing ratio.

And now I'm curious what emmvette had goin' on there...