How Do You Fit Additional Immobilising Relay to Car with Start/Stop Fuel Saving?

[geraintv]

Hi,

Is it possible to fit an extra immobilising relay* to amodern car loom with start-stop fuel saving?
(in addition to the manufacturers standard immobilisingsystem)

This is the logic that I’d like =

Initial turn of key = only start engine if fitted securitysystem is happy to start AND secondary immobiliser relay is ‘ON’
Stop-Start operation = work as normal and pay no attentionto secondary immobiliser relay state

Can anyone help?

Thanks in advnce!

 

[Darkwood]

Welcome to the forum

 

[snowhead]

This is the logic that I’d like =

Initial turn of key = only start engine if fitted security system is happy to start AND secondary immobiliser relay is ‘ON’
Stop-Start operation = work as normal and pay no attention to secondary immobiliser relay state

Can anyone help?

That's some weird contradictory logic you're asking for there.

And impossible to achieve.

In order for stop start to take effect several conditions have to be met, including (but not exclusively) engine up to temp, battery voltage not low and hill start assist not active.

If the secondary immobiliser was active the vehicle wouldn't start, so you couldn't get to the point of stop start being available.

If you want a secondary immobiliser you can interupt the Can-bus (or whatever Bus comms it's using) link from the immobiliser module to the Ecu.

 

[geraintv]

Welcome to the forum

Thanks Darkwood!

 

[geraintv]

Many thanks for replying snowhead.

At the minute my poject piece is not allowig the starter solenoid to operate when the vehicle is initially started IF a valid nfc tag has not been shown to nfc reader. This secondary starter immobliser relay resets to not allow the the starter solenoid to operate once theignition is turned off – hence my problem with my design not working with carsfitted with fuel saving stop-start.

I’m trying to avoid the CANBUS>OBD solution as this wouldadd extra cost to my ‘on a very low budget’ approach!


Really appreciate your and any one elses advice

 

[telectrix]

simplest way is to fit a kill switch in the feed to the starter

 

[snowhead]

This secondary starter immobliser relay resets to not allow the the starter solenoid to operate once theignition is turned off – hence my problem with my design not working with carsfitted with fuel saving stop-start.

How are you disabling the starter solenoid,, From the ignition switch?

Stop Start doesn't turn all the ignition circuits off, it kills the engine run signal within the ECU.

Everything else stays on, Dashboard, heater brake lights etc.

The restart from stop is initiated by the clutch pedal switch or if the Ecu detects low battery state.

My Can bus suggestion was to fit a simple relay to break the wires between the Ignition key module and the ECU.
Nothing complicated or expensive.

 

[geraintv]

gotcha! the penny has dropped

I'l give that go and report back

Cheers!

 

[PEG]

Hi,has not the vehicle got the facility to turn stop/start system off?

Any addition to a modern vehicles electrical system,runs the risk of enabling a fault code,to be logged.

...anyway,who steals a vehicle on your island? You could stand on one bridge,and watch the other one,AND the petrol-station they'd have to visit...:love:

 

[snowhead]

Hi,has not the vehicle got the facility to turn stop/start system off?

My van is 1 time only turn off, then reset when the ignition is turned off.
I'd guess they're all similar.