Unlike in some cars such as VW’s, in a Subaru, the engine management wiring is not conveniently in a separate wiring harness which you can just take out and use in another car with minimal modification. The wiring in a Subaru is split up by location in the vehicle, not by function, and this means that to make the Subaru engine run outside of the rest of the Subaru, some work is involved to make an ‘engine management only’ harness from multiple much larger Subaru harnesses.
Price: from £297.50 GBP +VAT (£357.00)
Having the engine management wiring work done properly, by someone who knows what they are doing is the one main thing which has the biggest effect on how successfully your Subaru engine will run in your VW. The cost difference between having it done properly and having it done badly is typically not big in the scheme of things (in some cases it will be cheaper to have it done properly – if you do your homework on who to have do the work up front). Why cut corners here? You’ll likely regret it later – we know this as we quite frequently get calls from unsatisfied customer of others’ wiring work, looking for issues they are having with the wiring to be fixed.
We work on all of the pre CAN bus European / ‘rest of world’ spec Subaru engine management systems. This means all except the US spec models post MY94 and most Japanese spec models (although we can do certain 1990’s Japanese models).
We can usually turn harnesses around withing 1 to 6 weeks depending on workload. Typically, it averages around 3 weeks.
We can also do the automatic transmission wiring work for conversion using Subaru auto gearboxes, but only at the same time as we are doing your engine management wiring work, and only if all the engine and gearbox hardware is from a single Subaru donor vehicle.
Harness work options:
All of our Subaru engine management wiring work options are designed to either make the wiring easier to install into VW’s, or as replacements for VW or Subaru standard parts which are either often missing or were not in all models, but make installation easier.
Front Extension Harness
Price: from £100.00 GBP +VAT (£120)
We came up with the concept of the front extension harness back in 2008 to extend all of the features which have to be or should be in the front of a rear engined VW from the engine management in the rear when it became apparent that most customers were not happy with extending these to the front themselves. The concept has been copied since, including by competitors who publicly claim not to be copying our work, despite them being foolish enough to copy out name for them too.
Front extension harnesses are not a product which can be purchased separately – they are only available at the time we do your engine management wiring work because they include the necessary connectors and wiring work so they can plug in to your Subaru engine management. We aim to keep them as standard as possible, but some specification choices do affect some of the front extension harness details, so they’re made to suit each customer’s exact conversion spec. They’re entirely made from new parts (no VW or Subaru parts needed), as this is neater, and there isn’t really a way to make them from used Subaru and VW parts economically. We make front extension harnesses for the following VW models:
- T25 / T3 / Vanagon
- Split screen bus
- Bay window bus
- Beetle (customers have also used these, or minor variants of them in Trekkers an Karmann Ghia’s, etc. Not what they were originally designed for, but they’re obviously dimensionally nearly identical to Beetle’s)
Depending on the spec of the conversion they extend the following features to the front:
- Engine check light
- Immobiliser light
- Vehicle speed sensor
- Rev counter signal
- Radiator fan control
- Fuel pump
- Temperature gauge signal
Almost every customer goes for a front extension harness – they make getting all the necessary wiring to things forwards of the engine management very easy
Built in New VDO Coolant Temp Gauge Front Extension Harness Option – for air cooled VW models
Optionally all front extension harness variants can also be supplied with a new 52mm dual scale VDO Cockpit coolant temperature gauge, pre-wired so the gauge just plugs in and reads correctly. Standard VDO gauges are not compatible with the Subaru temperature senders, and VDO never made a sender which fits the Subaru gauge sender thread*, so not only does this option save you having to wire an aftermarket temp gauge into your originally air cooled VW, but also saves you having to find a way to install it’s sender. The only wiring you’ll need to do to the gauge is joining its (included) bulb to your VW dash illumination circuit so it lights up when you turn your lights on. This option costs hardly any more than you would pay elsewhere for a VDO gauge without a sender because we got a very large job lot of gauges many years ago for the right price.
* in the Phase I and very early Phase II models which have a tapping for a separate gauge sender
New VW Connectors on you Subaru Engine Mangement Harness
Price: £30.83 GBP +VAT (£37.00)
This option is a set of things which makes the Subaru engine management plug in to the VW connectors in watercooled T25 / T3 / Vanagon models. You’ll probably think the low price is a mistake – it isn’t. More info on that later. It includes:
- Fitting all the right VW connectors (of the 12 possible combinations) to plug in in your engine compartment junction box.
- Fitting the correct low coolant level sensor connector to suit your VW and the wiring to it so the low coolant level system works as exactly as VW intended.
- Wrapping the harness in tape and conduit to OEM specs. This is only viable once the exact routing of the harness in the VW is determined, and for the water cooled models where the engine management plugs in to standard VW connectors, the exact routing isn’t defined until all the relevant VW connectors are fitted. If you don’t go for this option, the harness tape and conduit are supplied loose, for you to fit once you’ve determined the exact routing. We use premium quality tape (3M or Scapa) and new conduit (Harnessflex), and the objective is to wrap the harness to the same spec as it was when it was in the Subaru.
- Bespoke bulkhead grommet fitted to the harness. Our latest grommet design can be fitted into either a flat body panel or the VW 40mm pitch corrugated floor, with both requiring the same 52 x 90mm slot with full radius ends, for which we can supply a marking template if required.
- Coolant temperature sensor extension cable for conversions using a reversed coolant manifold.
No used parts from your VW wiring needed – we use all new connectors where the wiring plugs into the VW. There are a couple of reasons why this option is so inexpensive. Firstly we source the connectors required much more cheaply than anyone else doing similar work is likely to. Secondly, in our opinion, this option combined with a front extension harness is the right way to install Subaru engine management into the water cooled VW models – plug and play with no modifications to the VW wiring, and we want to encourage all customers to go for it. This works – almost every customer goes for this option.
Only available as an option with our harness work – we don’t sell the individual parts used individually.
Fuel Pump Harness
Price: £10.83 GBP +VAT (£13.00)
Late model fuel injected T25 / T3 / Vagagons (1987 –>) had a separate harness for their fuel pumps. This ran from the RH front corner of the engine compartment in 2wd models to the pump, or from the engine compartment junction box to the pump in Syncros. Initially we just stocked the VW connector so we could fit it to the Subaru engine management harnesses and the original VW fuel pump harnesses could plug in, but then realised it made sense to offer a reproduction of those harnesses too as they’re a neat way to withe the pumps in earlier or non injected models which didn’t originally have them.
Fuel pump harnesses are not a product which can be purchased separately – they are only available at the time we do your engine management wiring work because this includes fitting the necessary connectors for them to plug into.
You need to specify whether you are using a ring or a spade terminal fuel pump when ordering.
Rev Counter Interfaces:

Rev Counter Interface Kit for DIY installation (part no. 100-00005), Price £26.25 GBP + VAT (£31.50)
Rev Counter Interface harness option – built into your wiring harness when we do your harness work (part no. 110-00003), Price £31.67 GBP + VAT (£38.00)
Many older designs of rev counters, including the standard VW T25 / T3 / Vanagon petrol rev counters, require the high voltage signal from the VW coil negative terminal. The Subaru pre CAN bus ECU’s and many others from the same era such as VW’s GTi and TDi ECU’s give put a low voltage signal for the rev counter, so can’t drive these older rev counter designs directly. We designed this rev counter interface specifically driving the VW T25 / T3 / Vanagon petrol rev counters from Subaru ECU’s after having previously used other methods and similar products made by others, none of which were ideal. They also suit may other applications where a rev counter designed only to run from the high voltage coil negative terminal signal in a 12/14.7V vehicle needs to be driven from a 3-14.7V square wave.
The interface does not change the rev counter calibration. The VW rev counter has calibration adjustment built in, which can be when using an engine with a different number of cylinders. This requires an accurate means of measuring the engine speed such as a diagnostic tool.
Can be wired anywhere between the ECU and rev counter – does not require disassembly of the dash instruments, which risks damaging the very fragile flexible blue circuit board, which is a major advantage relative to some other methods.
Not suitable for diesel rev counters.
Subaru Cruise Control
Price: from £166.67 GBP +VAT (£200.00) for cable throttle Subaru models
If your donor Subaru had factory fitted cruise control, it can be used in your VW if you want it. Like front extension harnesses, cruise control is not a product which can be purchased separately – it is only available at the time we do your engine management wiring work because it include the necessary connectors and wiring work so they can plug in to your Subaru engine management. We can only add it at the time we do your engine management wiring work, or if you send the engine management hardware back to us at a later date (so we can install the necessary fuse, wiring and connector). Includes all parts to mount the cruise control hardware.
Our Subaru cruise control requires the use of your own cruise control ECU and actuator, etc. However, our cruise control wiring harnesses are no longer based on used Subaru parts*, but are made from new components. This is for two reasons:
1. the time taken to extensively modify the original Subaru wiring to fit a rear engined VW is both excessive
2. basing the wiring on the used Subaru parts cannot result in a neat end product, as so much has to be extended to position various parts at opposite ends of the vehicle which were close together in the front engined Subaru.
This also means you can easily have cruise control in your VW if the engine donor didn’t have it (for example in the UK, cruise control was not available in Imprezas). You just need to source the ECU, actuator etc separately, and these are usually available inexpensively.
Our Subaru cable throttle cruise control retains all of the functionality and features of the system in the Subaru, including diagnostics. We also offer an option which combines all of the cruise control user interface into the control stalk, meaning there is no need to have a relatively ugly (well, they don’t match the VW dash styling) Subaru cruise control on / off switch, or to mount a cruise control on / off light elsewhere in the dash.
See Subaru Cruise Control for more information.
Lambda / Oxygen / O2 Sensor Adaptor and Extension Harnesses
Lambda extension harnesses: Price: POA (usually made to order, to your length requirements)

We stock the new connectors to make extension cabled for almost all of the (many) Subaru lambda sensors. These are not ‘off the shelf’ products – they’re made to order for each customer. You have to tell us how long you need the extension cable to be and what connectors your sensor uses (if we don’t have your harness here at the time).
Through the Subaru engine management harness, the low level lambda / oxygen / O2 signal uses screened cable to keep out interference from other nearby circuits. Also, the wires on the lambda sensor itself are not copper, so are not easily soldered. Both of these make extending the wiring to the lambda sensor, if required by your exhaust routing, difficult. Also, because the signals are very low level, they are more prone to stray resistance from dodgy connections (such as trying to solder to the non copper wires). The best way to extend the lambda sensor wiring if required is via a plug in ‘extension lead’.
By default out lambda sensor harness extensions do not used screened cable, just like the ones used in certain Subaru models didn’t. They’re intended to be routed away from other wiring.
See Subaru Lambda / O2 / Exhaust Oxygen Sensor Information for more details on the lambda sensors which suit various Subaru engine management systems widely used in VW conversions
Lambda adaptor harnesses: Price: POA (often made to order, to your length requirements)
Various Subaru models use short adaptor harnesses between the main engine management harness and the sensor(s). Some of these effectively just change the connector and slightly extend the wiring. Others split out a single harness connector for two lambda sensors. These are sometimes missing when customers buy the parts from a donor car – usually because that car was in a breakers yard, and they’d already removed the catalytic converter(s) to sell them, leaving the sensors and adaptor harness attached to the cats. These are two examples of the genuine Subaru parts that our reproductions replace:
- Wideband and narrowband lambda adaptor
- Wideband only lambda adaptor
We can make lambda adaptor harnesses either as direct replacements for missing Subaru parts, or can they can also be custom made to non standard lengths. This can eliminate the need for also having lambda extension harness.
See Subaru Lambda / O2 / Exhaust Oxygen Sensor Information for more details on the lambda sensors which suit various Subaru engine management systems widely used in VW conversions
Immobiliser Antenna
Price: £50 GBP +VAT (£60)
If you have the MY00 onwards engine with the Mitsubishi immobiliser, but don’t have, or don’t want to use the key and lock barrel assembly in your conversion project, we make a new immobiliser antenna which reads the transponder chip without the key body or ignition lock barrel being present. These are far smaller and neater then using the key and ignition lock barrel, but are not suitable for use when you want to use the immobiliser to immobilise your VW. Originally designed for customers who do not have the key body or ignition lock barrel – just the ECU, immobiliser ECU and transponder chip:
Transponder chip and immobiliser ECU not included. Only available as an option with our harness work – not sold individually.