Does any have a Wiring Diagram for a Sigma vtti race car - 2014 onwards

[Northern Banana]

This is possibly different to the road car of the same age, as for example, the race cars fuel pump primes on the masterswitch, even with the ignition switched off.

Seems to have only 4 relays rather than the 6 on the standard wiring diagram.

TIA

[Jonathan Kay]

This one only has four relays side by side.

Jonathan

0900167 Sigma TA 2013 Chassis Harness.dwg__0.pdf

[Northern Banana]

broken image link

[Jonathan Kay]

Shows OK for me: probably that known site bug of variable display of PDFs that depends on the client browser.

Jonathan

[aerobod - near CYYC]

I had to right click on the image and "open image in new tab" to get it to display in Firefox on Linux.

[Jonathan Kay]

Same file as .png.

[Northern Banana]

That looks like the correct one.  Thanks. 

The cooling fan isn't run via a relay and the loom doesn't have a take off for a separate fan switch.

 

 

[aerobod - near CYYC]

So this looks like an MBE 9A6/9A9 style ECU, with Pin 116 directly driving the rad fan. I would still suspect grounding or power supply issues before an internal ECU problem. Pins A1 and A2 (black/yellow wires) should always have a fraction of an ohm resistance to the battery negative and engine block and from the ring terminal they attach to (which should be within 250mm of the ECU). Pins A4 and A5 (white/orange wires) should always be at battery voltage when the ignition is switched on and pin A3 (pink/green wire) should always be at battery voltage at all times if the isolator is on. I would wiggle all wires and loom near the ECU to ensure the resistance or voltage doesn't change due to a fractured wire or loose connection.

[Northern Banana]

Thanks James and Jonathan,

Some progress made - found a 'stretched' black and yellow earth wire drivers side of the battery (ecu ground I suspect).

Not getting voltage drops now,  for reference the constant voltage to the rad fan is still there, so maybe it is a variable voltage/speed type.

Still got a negative air temp sensor reading. The sensor is functioning as when I blow a hair drier in to the air intake it shifts.  Don't think I can recalibrate it in easimaps and wiring looks ok. Job for tomorrow.

[aerobod - near CYYC]

I think your residual voltage may just be micro-amp level leakage past switching transistors within the ECU (which you wouldn't see with a relay). The air temp sensor is worth investigating, but perhaps with the racecar implementation, the map is not using air temp, so it may default to the default/"failed" value, as it does with the barometric pressure.

The other thing with the temp sensor is it may be the wrong one from a resistance curve perspective, MBE typically use Bosch resistance curves for the default mapping, mine reads 3.57V when registering 20C, which should correlate to a resistance of 2,500 ohms, looking at the Bosch temp sensor curves.

If your temp sensor has a resistance of about 8,500 ohms when Easimap is registering -8C, then the ECU is using a Bosch temp curve and the sensor is the wrong one if the air temp is around room temperature.