K Series EU3 Engine Loom Wiring Diagram - Updated/Corrected

Having recently built a spare K-Series engine I had need to make an engine wiring loom from scratch. Working from the published Caterham K Series EU3 Wiring Diagram I found several problems:

i. The diagram contains numerous errors, some of which are just irritating (e.g. ECU plug pin layout is neither a front or rear view but a mixture of the two) and some of which are serious (e.g. the VVC cam sensor wires are shown reversed and the LT coil pack connections are shown swapped over between the coil packs).

ii. Wiring which is shown as being the same on all cars actually varies between different examples. In particular the Main Relay in the MFRU is used in some cars and unused in others, as discovered when some people found additional wiring while implementing my K-Click modification.

iii. No part numbers or sources are shown for any of the connectors. Although many are standard series connectors, some such as the ECU plugs and engine loom to injector loom headers are more difficult to identify. Rover part numbers are now of little use - OEM part numbers are required.

iv. No specifications are shown for wire sizes. This may not be important when fault finding but are required when fabricating a new loom or replacement sections for repairs.

v. (Most of) the connector pinouts are drawn looking at the front face of the plugs. when building a new loom I was mostly inserting wires into plugs from the back, and therefore had to keep swapping round all the pinouts in my head. It would have been much more useful if the pinouts were shown looking at the plug from the wire side.

vi. The diagram contains information relevant to all models, much of which is not relevant to my loom. For my purposes it would have been nice to be able to "switch off" the wiring for options which I did not have. In addition the diagram shows discreet wiring which is not part of the loom, e.g. battery and starter cables, and it would have been nice to have been able to switch these off too.

I have therefore completely reworked the wiring diagram to address all of the above and wanted to share it back to the club membership as I felt others may find it useful. I have done it as a Paint.NET project (free download for Windows here) with each of the options in a separate layer, so you can switch on and off the options relevant to your car and get a specific customised wiring diagram. I have also made flat .PNG versions of it, showing all optional wiring, in two flavours (with or without the Main Relay wiring).

Download Links:

· Paint.NET Project

· Full Flat .PNG (With Main Relay)

· Full Flat .PNG (No Main Relay)

· Separate Layers

To check whether your car has the Main Relay wired in the MFRU, compare the wires connected to the plugs on the MFRU (on top of the ECU) with this diagram - if you have an extra Brown (or sometimes Brown/Blue or Brown/Pink) wire on Pin 8/8 like this then your Main Relay is used (this allows the ECU to completely disconnect the supply to the engine electrics such as injectors and coil packs and reduces battery current drain through leakage).

i. All of the known errors have been corrected. A VVC 160 engine wired exactly as per this diagram certainly runs happily. If anyone does spot any errors or omissions, please let me know and I'll be happy to try to keep this up to date as a reference. Similarly there are areas of the diagram which do not apply to my car, in particular the extra wiring for Apollo and Dry Sump Stack systems where little detail is shown for connectors etc. If anyone is able to supply me with more information on these, again I will update.

ii. As described above, I have taken into account the differences in Main Relay wiring.

iii. I have tracked down OEM and part numbers for each of the connectors. Using these I was able to source a complete set of brand new connectors. Please be aware that with some connectors e.g. the multi-pin ECU plugs, there are other connectors which look almost identical but have slightly different terminal sizes etc. The part numbers shown are believed to be correct.

iv. Wire colours and sizes are shown for every wire. For every single wire I both took measurements off my loom or old looms which I stripped down, then cross referenced the results with original Rover circuit diagrams. when building my loom I found it difficult to source wires in all colour combinations on 0.5mm² and 0.75mm² sizes, so substituted 1.0mm² wires for these. Although this may make the loom slightly bulkier that if the original sizes were used, the number of redundant wires which I was able to omit made up for this. The only issue was that clipping the back covers onto the ECU plugs was a little tight, but manageable.

v. On my diagram ALL CONNECTORS ARE DRAWN VIEWED FROM THE WIRING SIDE, NOT LOOKING AT THE CONNECTOR FACE. This was primarily because I drew the diagram for the purposes of constructing a new loom and this was the most useful view for me, however it is different to the convention (mostly) used by Caterham. It is at least consistent throughout.

vi. PLEASE NOTE THAT THIS DIAGRAM APPLIES TO EU3 K SERIES ENGINES ONLY.

The layers available in the Paint.NET version are:

i. "Background" - Plain white background. You will always want to switch this layer on.

ii. “Notes” - Notes, keys, legends and logos. You will always want to switch this layer on.

iii. "Common All Models" - As the name suggests, this layer contains wiring which is common across all K EU3 engine installations. You will always want to switch this layer on.

iv. "MFRU Output Pin 8 Used" and "MFRU Output Pin 8 Unused" (ONLY SELECT ONE OR THE OTHER) - These layers contain the two different Main Relay configurations as described above.

v. "EU2-Style IAT (No 4 Runner)" and "EU3-Style IAT (Within MAP)" (ONLY SELECT ONE OR THE OTHER) - These layers contain the two different Intake Air Temperature Sensor configurations. The "EU2-Style IAT (No 4 Runner)" configuration is incorrectly described on the Caterham diagram as being "VVC Models Only" and the "EU3-Style IAT (Within MAP)" configuration is incorrectly described as being "Not VVC Models". As far as I can determine, for EU3 engines only VVCs originally destined for Pre-2004 MG ZRs had a separate IAT sensor on the lower inlet manifold. I believe this was as a result of using up old stock castings from earlier engines. If your engine has a green IAT sensor like this and this on the lower inlet manifold AND IT IS CONNECTED, you will want to switch on "EU2-Style IAT (No 4 Runner)", otherwise switch on "EU3-Style IAT (Within MAP)" (NOT both). WARNING: When I got my car it had no sensor on the lower manifold, however it did have an unused plug dangling where the sensor would have been. The ECU inputs were wired to this (i.e. I was wired according to "EU2-Style IAT (No 4 Runner)") instead of being wired to the combined IAT/MAP sensor. When I connected and OBDII scanner up it showed an IAT of -40C and an IAT fault logged. The engine was permanently in LOS (limp) mode with adaptive fuelling disabled. The engine fitted was clearly not the one the car was wired for. I rewired the loom according to "EU3-Style IAT (Within MAP)" and everything was happy. I mention this because other people may find this or the opposite - an unused sensor on the manifold, as older manifolds may be fitted to later engines, in which case the sensor may be present simply to plug the hole but the engine will be using the combined IAT/MAP sensor.

vi. "VVC Mechanisms (VVC Only)" and "Cam Sensor (Non-VVC)" (ONLY SELECT ONE OR THE OTHER) - Switch on "VVC Mechanisms (VVC Only)" if you have a VVC engine, otherwise switch on "Cam Sensor (Non-VVC)" which contains wiring details for the 3-pin camshaft position sensor used on non-VVC engines (which use a 2-pin camshaft position sensor)

vii. "Emissions Ctrl (Non-UK)" - This layer contains details of emissions control systems not fitted to UK models including the charcoal canister purge valve and post-cat oxygen sensor. Only switch on this layer for export models which do have these systems fitted.

viii. "Shift Light (Supersport)" - This layer contains details of the shift light fitted to Supersport models only. From what I can see, this was implemented by reprogramming the ECU to turn on the AIR CONDITIONING at the RPM limit, and the air conditioning output of the ECU was then cunningly wired to the shift light.

ix. “Stack Dashboard” - This layer contains details of the additional wiring for models using the Stack dashboard only. As mentioned above, some additional systems were not implemented on my car so I was unable to add much detail over and above that on the Caterham diagram.

x. "Oil Temp Sensor (Apollo & Dry Sump)" - This layer contains details of the additional oil temperature sensor fitted to models with Apollo and dry sump oil systems. As mentioned above, some additional systems were not implemented on my car so I was unable to add much detail over and above that on the Caterham diagram.

xi. "Injectors & Coils (Sub Loom)" - This layer contains details of the separate injector and coil pack sub-loom. This will be present on all cars but I included it as a separate layer as I wanted to be able to produce a diagram for the main loom only. Switch this layer on or off according to whether you want to show the sub-loom.

xii. “Yazaki Type Sub Loom Connectors” - This layer contains details of the Yazaki type connectors used on the ignition and injection sub-loom on some vehicles. If your injectors and ignition coils are on separate sub-looms with separate connectors into the main engine loom, switch this layer on. If your injectors and ignition coils are on a single sub-loom with a single locking connector into the main engine loom, switch this layer off.

xiii. "Discreet Wires (Not In Loom)" - This layer contains details of discreet wires which do not form part of the main wiring loom, such as alternator, battery and starter connections. As above, this will be present on all cars but I included it as a separate layer as I wanted to be able to produce a diagram for the main loom only. Switch this layer on or off according to whether you want to show external wiring.

I hope this is of use to people. Please feel free to feed back comments and corrections which I will endeavour to incorporate into the diagram as and when I get the time.