Hi everyone,

I was having a thought of connecting 2 ECU's with different mappings to a car, and be able to switch between them before starting the car.

Will this be possible with either SRR, SPST. I was thinking of something like a Darlington array, but with relays or switches instead of transistors.

I was thinking of making 2 circuits one for each ECU. I will have to switch between around 45 wires/switches. does anyone know about a suitable Switch array etc? i havent been able to figure out what would be best? The voltage running in the wires is between 3.5 and 12 volts.

I have found some 2 channel NO/NC SRR IC's, but would prefer 4+ channels.

The ECU has to be able to communicate both ways with the car. Sensors etc..

I have attached a simple sketch.

I hope someone can point me in the right direction.

Best Regards

 

Let's assume we've solved the switching challenge ... somehow. Are you certain this ECU switching can work? I believe on my car the ECU talks to the other modules such as the BCM, and won't work unless various security handshakes are accepted. I don't recall all the details, only that swapping an ECU is not a trivial matter. I though I had an ECU problem once and had to order an ECU from a custom programming shop. It never did work and I returned it. Fortunately for me I discovered the problem was elsewhere.

 

Thank you for the quick reply.

The ECU's will be cloned and immobiliser will be removed. So that only the mappings that are different.
It's an old VW 2.5TDI Bosch EDC15.

So i think it would be possible, just like switching the ECU's manually by hand.

 

So i think it would be possible, just like switching the ECU's manually by hand.

I'd certainly verify that by hand before building a switch.

The first thing that popped into my head was a box we used to have for switching between hard drives. This was back in the days of SCSI, so I think it was a 50-conductor switch. That would handle your ECU wires.

 

What year is this vehicle? Technically you could wire up everything in parallel except for power, ground and communication. All inputs and outputs could be hardwired to both. You just need a way to take power away from one, and power up the other. If it is newer, it gets more complicated because ECMs have to have the same operating systems but can be programmed differently. In recent years, that is almost impossible as the ecm is serialized to the vehicle and only the best programmers can get you into that territory. This should be fairly easy to do if it is olddr vehicle.

 

Technically you could wire up everything in parallel except for power, ground and communication.

You would have to ensure that absolutely no signals were applied by the powered ECU to the unpowered ECU, since the signals on I/O pins of some unpowered ICs are capable of part-powering the IC and causing malfunction or chip damage.