Tach no work

[Raul_Chile]

I have problem with my 2008 LY6. I have repinned a wire to pin 48. In HP tuners I have flashed it to "crank" and 15/15. Using resistors for a pull up signal around 1K and a switched 12volt wire I get nothing. I have tried with 3 tachometer different and nothing.

I have other problem that I don´t know if is relationship with Tach. My speed gauge(on HPTuners) show always 252 km/hr

attach file HPT

Best Regards

[Shrek]

The tune you posted is for a 2008 LY6 6.0L - but it would have initially been paired with a 6L90, and was a 4x4 calibration.

Regarding your Tach - make certain you have inserted your Tach output wire to C1 (Black) pin 48 - not difficult to be off by one cavity with the E38 / E67 connectors. The Tach settings in the tune are correct to output a 4 cylinder type Tach signal.

If you hold C1 by where the harness enters the connector, such that the wide ground pin (73) is in the upper right corner, pin 48 is the 5th pin down from the top, in the second row in from the left edge of the connector.

There is no automatic transmission portion in the tune you posted - are you using a manual transmission ?

What wiring harness are you using, and how have you adapted it ?

Some 4x4 used a Rep TOS type VSS signal from the 6L90 to the E38 - which would then generate a speedometer output to the IPC. Other 4x4 used a transfer case mounted VSS - wired directly to the E38.

A little more information about your project would help generate possible solutions.

[Raul_Chile]

The tune you posted is for a 2008 LY6 6.0L - but it would have initially been paired with a 6L90, and was a 4x4 calibration.

Regarding your Tach - make certain you have inserted your Tach output wire to C1 (Black) pin 48 - not difficult to be off by one cavity with the E38 / E67 connectors. The Tach settings in the tune are correct to output a 4 cylinder type Tach signal.

If you hold C1 by where the harness enters the connector, such that the wide ground pin (73) is in the upper right corner, pin 48 is the 5th pin down from the top, in the second row in from the left edge of the connector.

There is no automatic transmission portion in the tune you posted - are you using a manual transmission ?

What wiring harness are you using, and how have you adapted it ?

Some 4x4 used a Rep TOS type VSS signal from the 6L90 to the E38 - which would then generate a speedometer output to the IPC. Other 4x4 used a transfer case mounted VSS - wired directly to the E38.

A little more information about your project would help generate possible solutions.

first specs and picture

Wrangler TJ
LY6-2008 (Out Silverado 2500HD)
T56 - Corvette 94
Adapter T56/D20 in house
Tranfer Case Dana 20
F44 front
F9 rear Detroit locker
33x12.50 Dunes Grappler

[Raul_Chile]

more picture and videos

http://www.youtube.com/watch?v=qVZsb...KCDbA&index=44

http://www.youtube.com/watch?v=oFWfE2DxvAU

.......

[Raul_Chile]

The tune you posted is for a 2008 LY6 6.0L - but it would have initially been paired with a 6L90, and was a 4x4 calibration.

Regarding your Tach - make certain you have inserted your Tach output wire to C1 (Black) pin 48 - not difficult to be off by one cavity with the E38 / E67 connectors. The Tach settings in the tune are correct to output a 4 cylinder type Tach signal.

If you hold C1 by where the harness enters the connector, such that the wide ground pin (73) is in the upper right corner, pin 48 is the 5th pin down from the top, in the second row in from the left edge of the connector.

There is no automatic transmission portion in the tune you posted - are you using a manual transmission ?

What wiring harness are you using, and how have you adapted it ?

Some 4x4 used a Rep TOS type VSS signal from the 6L90 to the E38 - which would then generate a speedometer output to the IPC. Other 4x4 used a transfer case mounted VSS - wired directly to the E38.

A little more information about your project would help generate possible solutions.

1.-Yes, innitialy LY6 was 6L90 (Chevy 2500HD)
2.-repinned correct in Pin 48 C1
3.-I have manual transmission, T56 Corvette 1994
4.-Innitialy Allen Nelson re-programed PCM(tune hot-rod)
5.- I did harness modifing original chevy(I have prepared several harness TBI, Vortec, Ford, Jeep)
6.-About Red TOS VSS signal or TC mounted VSS I don´t know

What does about speed max 252k/hr?, It influence?

Regards
Raul

[Shrek]

6.-About Red TOS VSS signal or TC mounted VSS I don´t know

What does about speed max 252k/hr?, It influence?

Couple of things regarding VSS input / output ...

How (to which ECM pins) have you wired the VSS signal ?

In the tune you posted ... Speedometer>Vehicle Speed Output>Output Source ... is currently set to "Disabled" ... with a manual transmission this should be set to "RepTOS" ... and the remainder of the cells configured per a manual transmission.

The current tune is not outputting any VSS signal to the speedometer.

[Raul_Chile]

Couple of things regarding VSS input / output ...

How (to which ECM pins) have you wired the VSS signal ?

In the tune you posted ... Speedometer>Vehicle Speed Output>Output Source ... is currently set to "Disabled" ... with a manual transmission this should be set to "RepTOS" ... and the remainder of the cells configured per a manual transmission.

The current tune is not outputting any VSS signal to the speedometer.

I don´t have connected VSS, remember I installed old transmission T56 with tail housing, I out tail and put extension housing of transaxle corvette(see picture), this has not where to connect sensor VSS.

I have tried with enable/disable/Red TOS and nothing

Raul

[Raul_Chile]

sorry, pictures adapter T56

[Shrek]

How (to which ECM pins) have you wired the VSS signal ?

I understand this is a custom setup ... so whether you are using a tail stock VSS sensor, a transaxle VSS sensor, a cable operated VSS pulse generator, etc. - to which ECM pins did you wire the VSS High and Low signal ?

Without some type of VSS signal being generated and sent to the ECM there will be no speedometer output, and the ECM will assume the vehicle is forever stationary.

[Raul_Chile]

I understand this is a custom setup ... so whether you are using a tail stock VSS sensor, a transaxle VSS sensor, a cable operated VSS pulse generator, etc. - to which ECM pins did you wire the VSS High and Low signal ?

Without some type of VSS signal being generated and sent to the ECM there will be no speedometer output, and the ECM will assume the vehicle is forever stationary.

I don´t have connect VSS, remember T56 Corvette has not VSS sensor on tranny, It is on transaxle. Then I have not where put it.

Do you believe whether I don´t have VSS the PCM no shot signal by pin 48?

Raul

[hicksport]

I also have an LY6 with a t56 and I have had no luck getting the tach to work. I do not have a vss input either. Any ideas or input would be greatly appriciated.

[Raul_Chile]

I also have an LY6 with a t56 and I have had no luck getting the tach to work. I do not have a vss input either. Any ideas or input would be greatly appriciated.

We are two with the same problem

Please any help

[Raul_Chile]

heeeelpppp please

[Montecarlodrag]

Forget about Vss, it has nothing to do with RPM signal.
The tach output should give the same RPM you can see with a scanner.
The tach output may be damaged. You can test it with a voltmeter. Put it to AC volts and test while engine is running, it should give almost 5V.
An osciloscope is better.

If you get signal from tach output, then use a 680 ohm resistor to pull up. I have used 470 ohm resistors with some ECMs.

[Shrek]

I have other problem that I don´t know if is relationship with Tach. My speed gauge(on HPTuners) show always 252 km/hr

This part of his original post is VSS related.

Attempting to answer both his question about the Tach, and his question about why the scanner showed 252 Km/h (no VSS), appeared to cause the OP confusion.

Got tired of going in circles ...