This node proxies signals measured by other nodes and presents them to the instrument cluster and auxiliary warning lights in a manner compatible with the existing instrumentation.
The clock in the instrument cluster requires constant battery power (T28/11)
|Ignition On (15)||01.1||SC||Digital 8-bit||T28/13||Supply Power|
|Indicator Flash Signal||01.3
|Digital 8-bit||T28/24||LED supply in Cluster
Blink code on lamp failure
|Spare LED 1
|Spare LED 2
|Panel Illumination||06||DC||1-bit||T28/12||Supply Lamps PWM|
|High Beam Flash||02.0||SC||1-bit||–||OR with High Beam 02.1|
|High Beam||02.1||SC||1-bit||T28/25||Lamp supply in cluster|
|MFA Memory 1||04.0||SC||1-bit||T28/06||MFA in cluster|
|MFA Memory 2||04.1||SC||1-bit||T28/06||MFA in cluster|
|MFA Reset 1||04.2||SC||1-bit||T28/04||MFA in cluster|
|MFA Reset 2||04.3||SC||1-bit||T28/04||MFA in cluster|
|MFA Select||04.4||SC||1-bit||T28/15||MFA in cluster|
|Coolant Temperature||11||TM||Digital 8-bit||T28/23||Current sink from meter|
|Coolant Level||20.1||TM||1-bit||T28/02||Sink? Resistance?|
|Oil Temperature||102||TM||Digital 8-bit||T28/17||DAC? to MFA|
|Oil Pressure 0.3 Bar||100.0||FR||1-bit||T28/09||Sink|
|Oil Pressure 1.8 Bar||100.1||FR||1-bit||T28/08||Sink|
|Exterior Air Temp.||103||TM||Digital 8-bit||T28/01
|DAC? to MFA|
|Fuel Level||120||RB||Digital 8-bit||T28/21||Current sink from meter|
|Brake Fluid Level||101.0||FR||1-bit||K7||sink lamp|
|1-bit||K7||Flashes rapidly on Brake lamp fail when pedal pressed. – sink lamp|
|Parking Brake||07.5||DC||1-bit||K7||sink lamp|
The node senses cluster output signals for vehicle speed (T28/07) scaling it to km/h as an 8-bit number; engine speed (T28/10) in revs per second (8-bit) and engine manifold pressure. These values are made available as network objects.
As the bus speed is only 20 kbps maximum, it only has the ability to pass about 100 frames a second in total, before congestion may occur. So signals such as ignition pulses and the speedometer drive cable-equivalent can’t be passed easily. They would have to be sampled quickly at the measuring node and frames passed often just to keep the instruments updated. It would consume between 20% and 40% of total bandwidth.
Determining alternator state is integrated into the cluster. The signal cannot easily be proxied. After gaining some more understanding of the excitation of the alternator, the signal can be easily proxied via the J-Front node.
The brake warning light will, in addition to the fluid level and park brake warning, flash rapidly when the brake pedal is pressed and a fault has been detected with any brake light.
If there is an indicator lamp fault, the tell-tale LED in the instrument cluster will remain illuminated steadily whenever the ignition is on. When indicating, the tell-tale will cycle a twice the normal rate. Stopping the engine and switching on the ignition again without starting the engine will make the LED “wink” a code to indicate which exterior lamp has a problem. If there’s a fault on more than one, then it’ll cycle through all the faulty ones; nominally “clockwise” around the vehicle starting with the front-left.
The first additional feature is the immobilizer LED to be enabled in the instrument cluster. There are 2 spare LED locations which are accessible externally. “Some assembly is required”!
At the same time, the white lamp with blue filter, used to show high-beam operation can be replaced by a blue LED. Cluster illumination can also be addressed while the cluster is out of the vehicle and circuit taps investigated to e.g. extract manifold pressure readings from the transducer mounted on the back of the cluster.
Once it’s assembled, the node will provide immobilizer status by lighting a combination of the total of 4 LED directly under its control; the 2 newly inserted ones, high-beam and indicator. There’s also a brake warning lamp.
As the node controls many inputs to the instrument cluster, it can show extremely worrying things if the car is being driven with any of the key nodes showing that the immobilizer should be preventing the car from being driven. e.g. Rapidly-rising coolant and oil temperatures, brake failure, headlamps apparently flashing rapidly, indicators that always seem to be on and a fuel tank that empties very quickly.
This node will carry an ID chip and have a registered trust relationship with the immobilizer module. The presence and trustworthiness of the immobilizer module will be tested whenever the LINbus is woken up.