Active High/Low Inputs

On certain inputs, ignition voltage is applied to the input via a 'pull-up' resistor inside the instrument pack. This supplies a 'high' signal to the instrument pack input electronics. The signal can be pulled to ground by an external component.

Active Low
This is where the component controlling the input to the instrument pack is normally in an open circuit condition, allowing the input to rise to the 'pull-up' voltage (ignition). When a function is required to be active (e.g. a warning lamp to come on) the external component switches the input to a 'low' or ground condition, over-riding the 'pull-up'. The low must be 1 volt or less, relative to the instrument pack's ground connection, to activate the function.

Active High
This is where the component controlling the input to the instrument pack is normally in a 'low' or ground condition, over-riding the 'pull-up' voltage (ignition). When a function is required to be active (e.g. a warning lamp to come on) the external component switches the input to a 'high' or open circuit condition. The 'high' must be 5.0 volts or more, relative to the instrument pack's ground connection, to activate the function. If the input is open circuit, the 'pull-up' will raise the input voltage to ignition voltage and the resulting 'high' will activate the function.

Instrument Pack Schematic Diagram, Fig.1:

1 Speed Output 1
2 Speed Output 2
A Indicator Panel
B Gauges
C LCD Panel
°C Temperature Output - Air Conditioning Control Module (A/CCM)


Fault Warning lamp/'tell tale' does not illuminate when required
1. Switch ignition on and observe pack reset sequence. All lamps should illuminate. Renew any lamps which do not illuminate.
2. If lamp still does not illuminate under the required conditions refer to Pin Point Tests for relevant circuit checks.