Holden - Instrument Cluster

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Overview

The instrument cluster is a self-contained module in the dash featuring the speedometer, tachometer, fuel gauge, temperature gauge and usually a trip computer retaining information such as the odometer.

VT/VX/VY/VZ Commodores

Unlock Procedure

Before any configuration data can be read or written, the cluster must be in an "unlocked" state. This is achieved using a challenge-response authentication mechanism (also known as a seed/key pair). A seed can be requested from the cluster by issuing a Mode 11 request, followed by table number 00. The cluster will respond with Mode 11 and two bytes that form the seed. The key value is calculated and sent as a write to table 01 in Mode 11. For details on calculating key values, see GM Seed/Key. The tables below illustrate the unlocking procedure.

Seed request

Length (bytes) Field Value Notes
1 ID F2
1 Length 57
1 Mode 11
1 Table 00
1 Checksum A6

Seed response

Length (bytes) Field Value Notes
1 ID F2
1 Length 59
1 Mode 11
2 Seed S 16-bit Seed Value
1 Checksum c

Key transmission

Length (bytes) Field Value Notes
1 ID F2
1 Length 59
1 Mode 11
1 Table 01
2 Key K 16-bit Key Value
1 Checksum c

Key response

Length (bytes) Field Value Notes
1 ID F2
1 Length 58
1 Mode 11
2 Status Equals key K on successful unlock, FFFF on failure.
1 Checksum F8

Configuration Tables

Table Length Type Description
01 2 u16 Speedometer Pulses
50 1 Boolean Police Mode
67 1 Boolean Show Distance To Go
69 1 Boolean Show radio status
6D 1 Boolean Stopwatch
7E 1 Boolean Automatic Transmission