Instrument Auxiliary


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)

Signal Object ID Ex Type Terminal Note
Ignition On (15) 01.1 SC Digital 8-bit T28/13 Supply Power
Indicator Flash Signal 01.3
51.5+51.6
52.5+52.6
71.5+71.6
72.5+72.6
111.0+111.7
112.0+112.7
SC
FL
FR
RB
Digital 8-bit T28/24 LED supply in Cluster
Blink code on lamp failure
Spare LED 1
Immobilizer Status
01.6
73.3
201.6
121.7
SC
FL
FC
RB
LM?
1-bit T28/20 LED supply
Spare LED 2
Network Status
LM 1-bit T28/22 LED supply
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
T28/19
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
Service Brake 07.4
111.2+111.5
112.2+112.5
132.1+132.2
DC
RB
TG
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.

Immobilizer Functions

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.

Authenticated ID

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.

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