Speedometer Fluctuation

At road speeds between 160 and 180 km/h, fluctuation of the analog speedometer reading can occur due to interference occurring in the speedometer signal. The speedometer signal generated from the Transmission Output Speed Sensor (TOSS) may be corrupted due to interference from other vehicle electronic components. To correct this, it is necessary to revise the speedometer wiring circuit through a separate, newly introduced Vehicle Speed Interface Module (VSIM) which utilizes the wheel speed sensor signal as per manual transmission vehicles.

The new VSIM and patch wiring harness when installed utilizes the wheel speed sensor as the source of speed sensing signal (as per manual transmission vehicle).

The technical instructions found in this bulletin outline the process to install the patch harness and VSIM. THIS ACTION SHOULD BE TAKEN ONLY FOLLOWING CUSTOMER REPORT THAT THIS CONDITION HAS OCCURRED.

1. At branch with 6-pin male connector only:




1.1.	Cut off the connector.

1.2.	Cut off the black, red and orange wires and tape up ends.





1.3.	Keep white wire.




2. Plug in the two 24-pin male connectors from the VSIM harness into P/N AX199301 as shown above.



3. Remove the passenger compartment fuse and relay panel assembly. Refer to Chevrolet Service Information (SI).



4. Remove the instrument panel lower trim panel assembly. Refer to Chevrolet Service Information (SI).



5. Remove the instrument cluster trim assembly. Refer to Chevrolet Service Information (SI).



6. Remove the in-car air temperature sensor. Refer to Chevrolet Service Information (SI).



7. Remove the instrument cluster. Refer to Chevrolet Service Information (SI).



8. Insert the VSIM module and harness assembly (harness first) between the BCM and the HVAC duct. Pass the VSIM harness white wire (vehicle speed output) up to the instrument cluster location.



9. The VSIM harness white wire (vehicle speed output) must be routed up to the instrument cluster location.





10. Cut and tape back the purple-white wire into the instrument cluster harness. Splice the VSIM harness white wire (vehicle speed output) to the purple-white wire into the instrument cluster.







11. Splice the other branch of the VSIM harness into the PIM harness, adjacent to the fuse panel wire.



12. Insert the VSIM harness into the PIM harness (after spliced, soldered and taped together).



13. Remove the double-sided tape from the VSIM module and adhere to the BCM. Reassemble the vehicle.
14. Using the Tech 2®, reprogram the speedometer with the new PPK value. The Tech 2® steps are as follows:

Diagnostics > Model Year: 2006 > VZ/WL Series > Body > Instrument > Programming Configuration:

•	Engine Type = V8

•	Speedometer Pulses = see PPK column in table below

Then select "Program" to reprogram the speedometer.

VSIM and patch harness are supplied as follows:

VSIM module, P/N AX199301 - parts are available from regular service parts source.

VSIM module, P/N AX199301 includes both the module and harness, P/N 92199300.

One part is required per vehicle.

TBA