92 4l80e help

[94_chevy]

Speedo quit working on me, the transmission is in limp mode and have a parking brake light on now. Have replaced the VSS at the rear of the transmission (it’s a 2wd) and nothing changed, is there something I’m missing or is there something internal messed up?
It will work for for a min or 2 after letting it the truck sit while shut off.

 

[yevgenievich]

There are also input speed sensor. Had one fail to cause limp mode, but speedo worked

 

[stutaeng]

I think it's the rear VSS that sends signal to the ECU for speedometer. On a truck I did a 60 to 80 swap I wired them backwards and ECU was saying 24 mph while truck was in Park! LOL

BTW, can you hook up a scanner with live data capabilities and see what ECU is saying. Maybe your cluster is messed up?

Also worthwhile to check for codes...

On the parking brake light, have you checked your parking brake cable? I think they can sometimes hang up.

Not too familiar with the TBI trucks, but we have some guys here that are very knowledgeable on these...

Report back what you find.

 

[stutaeng]

I think it's the rear VSS that sends signal to the ECU for speedometer. On a truck I did a 60 to 80 swap I wired them backwards and ECU was saying 24 mph while truck was in Park! LOL

BTW, can you hook up a scanner with live data capabilities and see what ECU is saying. Maybe your cluster is messed up?

Also worthwhile to check for codes...

On the parking brake light, have you checked your parking brake cable? I think they can sometimes hang up.

Not too familiar with the TBI trucks, but we have some guys here that are very knowledgeable on these...

Report back what you find.

 

[94_chevy]

I think it's the rear VSS that sends signal to the ECU for speedometer. On a truck I did a 60 to 80 swap I wired them backwards and ECU was saying 24 mph while truck was in Park! LOL

BTW, can you hook up a scanner with live data capabilities and see what ECU is saying. Maybe your cluster is messed up?

Also worthwhile to check for codes...

On the parking brake light, have you checked your parking brake cable? I think they can sometimes hang up.

Not too familiar with the TBI trucks, but we have some guys here that are very knowledgeable on these...

Report back what you find.

Wouldn’t be able to due to running a EZ TCU and it will shift fine when the sensor is picking up the speed but goes into limp mode after a min or 2 after starting to drive. And I’ve noticed the brake light goes away when when everything is working fine then when the sensor stops detecting the light turns back on.

 

[94_chevy]

There are also input speed sensor. Had one fail to cause limp mode, but speedo worked

Don’t have a connection for the ISS

 

[Schurkey]

Speedo quit working on me, the transmission is in limp mode and have a parking brake light on now. Have replaced the VSS at the rear of the transmission (it’s a 2wd) and nothing changed, is there something I’m missing or is there something internal messed up?
It will work for for a min or 2 after letting it the truck sit while shut off.

When the speedo quit on my '88, I tried a VSS. Didn't make any difference. The speedo would work--or not work--completely at random.

Turned out to be the circuitry in the instrument cluster. Not the speedo itself, it was the circuit board it plugs into.

Your '92 may be different.

 

[thegawd]

are you sure your not dealing with a failed ignition switch?

 

[Supercharged111]

Or failed VSS buffer?