Audi A2 Conversion

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On this page we describe the conversion of an Audi A2 1.4i petrol to electric propulsion. We will use the following components:

Pin mapping

We start out by mapping out useful pins of the original wire harness.

The semi-oval connectors are used throughout the engine bay. Numbering scheme: all start with part number 1J09737xx. The last two digits define pin count, arrangement and size. Examples:

  • 1J0973702 - 2 pins, small
  • 1J0973733 - 2x3 pins, large
  • 1J0973703 - 3 pins, small.
  • 1J0973723 - 3 pins, large
  • 1J0973713 - 2x3 pins, small

So the last digits is the number of pins per row, second to last encodes number of rows and pin size. 0=1 row, small; 1=2 rows, small; 2=1 row large, 3=2 rows, large. The matching counterparts have an 8 in place of 7, e.g. 1J09738xx. When the part number ends in a G, the casing is keyed.


The ECU has two connector slots, a smaller one with pins 82-121 and a larger one with pins 1-81. Here we map out pins useful to us

VAG wire color codes.png
ECU pinout 1.4i (AUA, BBY)
# orig function our function wire color Engine connector
1,2 GND as is br
3 permanent 12V ro
4 ignition 12V as is ro/sw
5 Lambda (first) heater Reverse light loopback gr 733 1
28 From generator (maybe DF) li/bl
33 Throttle second pot GND as is gr/ge
34 Throttle second pot (signal) as is br/gn
35 Throttle first pot (signal) as is ge/bl
36 Throttle first pot GND as is br/ro
38 To cruise control switch * if installed ws
39 Clutch pedal sensor * if installed ro/ge
40/41 To Climate control display sw/ge sw/gr
43/54 To instrument cluster (function unknown) gn/sw bl/ws
51/52 Lambda (first) signal CAN for Prius bl/ws ge 733 6/3
55/56 Brake light switch NC/NO to +12V ws/ro ro/sw
57 To cruise control switch * if installed bl/ro
58/60 CAN-L CAN-H as is or/br or/sw
63 Lambda (second) heater Drive mode selection li/ro Cable from rear lambda
64 Charcoal filter solenoid vacuum pump GND bl/ge 722G moved to 722
65 Fuel pump relay- control ro/br
68/69 Lambda (second) signal Drive mode LEDs bl/br ro/li Cable from rear lambda
70/71 Lambda (first) signal dcsw (70), prec (71) bl sw 733 5/4
72 Throttle second pot 5V as is gr
73 Throttle first pot 5V as is ge/li
75/76 To cruise control switch * bl/sw sw/ro
82 Engine speed sensor gr/br
85 Intake manifold Temp/Pressure brake vacuum gr 704
86 Hall sender G40 signal ro/sw
87 Engine speed sensor gn/sw


Injector 1-4 sw/li li/sw

br/bl sw/gn




Throttle body senror

Throttle body sensor

Throttle body motor

ro/gn gn/bl

ro/bl li/ro

gn br/sw


2/4, 6/1, 3/5

93 Coolant temp sensor gr/ws
98 +5V wiring to engine bay as is gn/li 704
99 Knock sensor ws


EGR pot

EGR mot

fake oil pressure

Fake engine oil





102/103 Ignition coil bank 1/2 gn/ro - LIN gn/ws gn/ro 1J0973724
106 Knock sensor br
108 GND for engine sensors as is gr/ro
109 Intake manifold Temp/Pressure bl/gn

Many positions in the connector are vacant and we populate them with signals that we need to direct to the BMS in the back of the car. I'm using a CAT5 Ethernet cable for that. It is simply routed under the seat carpet.

Additional pins on unused positions
# our function wire color Comment
6 CANH to BMS bl
7 CANL to BMS bl/ws
8 Permanent 12V to BMS or
9 Switched 12V to BMS or/ws
10 Charging active to BMS gn/ws
11 Fuel tank simulation gn PB7 via NPN
12 DC switch HV+ br Forwarded from inverter (70)
13 Precharge relay br/ws Forwarded from inverter (71)
ECU pinout 1.6FSI
# Org Function Ours Color
1/2 GND br br
3/5 permanent 12V gn/ge gn/ge


First Lambda ge ro/ge bl/ge

br/ge li/gr

6 N290 Fuel metering valve ro/bl
7 Fuel pump relay control ro/br
8/10 CAN-H CAN-L or/sw or/br


NOX controller sw br/ws bl

ws/sw ge/ro

12 Heater output switch ge/br
13/17/30 Air mass meter gr/ro gr/ws li/ws
14 Thermo-switch for coolant circulation ro/ws


Throttle POT1/2 (signal/Gnd/+5) ge/li br/ro ge/li

br/gn gr/ge gr

23/46 Climate cotroler sw/gr sw/ge
26/45 Radiator fan controller sw/ge ge/gr
35 EGT ro/gn
36 Brake vaccum sensor bl/br
37 Sensors GND ge/bl
48/57 Brake light switch NO/NC ro/sw ws/ro
42 +5V to sensors ge/gn
49/51/52/55 Cruise control switch * If installed bl/sw ws sw/ro bl/ro
53 To airbag ECU ws/bl
59 Instrument cluster gn/sw
60/80 NOX heater br/ws br/ws
62/64 Current supply relay ro gr/ro
65 Generator DF li/br
67 Clutch pedal switch * if fitted ro/ge
78 N79 crankcase breather heater br


Coils ro/sw ro/bl ge/gn

ge/bl gn/ge

82/90 G28 Engine speed sensor gr/br gr/ro
83 G40 Hall sender br/bl
84 G71 Intake manifold pressure sens ge/ro
85/87/96 EGR sensor + motor li/gr li/ws ro/ws
86 Coolant temp sensor gr/ws
88 N316 Intake manifold flap valve li/ge
89 F265 Controlled cooling thermostat ro/br
91 G336 Intake flap potentiometer ge/ro
94 G247 Fuel pressure sensor gr
99 +5V to sensors li/ro
105 N205 Inlet Camsh. timing valve li/gn
113 N276 Fuel pressure regulating valve gn/bl


Throttle body li/ge li/gr ws

ro/gn ro/bl li

103/110/111 Knock sensor br br ws
106 Sensor gnd in engine bay gr/gn



Injectors 1-4 br/ge br/ws

br/gn br/ro

br/bl br/sw

Silence errors

Wave form to silence oil level warning

After disconnecting the engine and removing the ECU we have 3 errors: Low coolant level, low oil, ABS/ESP. Coolant level can be silenced by simply shorting out the corresponding sense pins. We will use the coolant reservoir of the Prius inverter. We might insert a sensor for super neat integration, but not for now.

ABS is solved just like in Touran Conversion

Same goes for oil pressure. With the sense line permanently shorted to GND we get an error at 0 rpm, with it open we get an error above 500 rpm or so. So we generate a signal that only pulls to GND above 700 rpm. I inserted the single pin into the grey 6-pin connector and bridged it to the VCU-generated signal on that same connector.

Low oil can only be cured by supplying the required signal:

I simulate the signal with a simple IO pin that is toggled "manually" as the time constants are rather long.