One of the most critical wiring aspects of your engine conversion wiring is the main relay. The purpose of this relay is to switch power to the ECU, the relay itself is controlled by the ECU. Essentially, the ECU decides when to power itself and when not to. It is important that this logic is retained in your wiring setup.
When you turn the ignition on, the main relay should turn on.
When you turn the ignition off, the main relay will turn off after approximately 20-30 seconds. It is important that you do not turn off or remove power from the ECU before the main relay has turned off. This includes battery isolators, disconnecting a battery, etc. Failure to follow this rule will probably end up in your EWS emulator coming out of sync.
When it comes to wiring up the electric pre-supply pump, you can either have it ECU controlled or just run it from an ignition feed. Running from an ignition feed can often be simpler and is one less point of failure; you know that when your ignition is on then your pump should be running. When ECU controlled it will turn off automatically after 30 seconds if the engine is not started.
Main relay wiring
On DDE 4 ECUs the main relay loom is usually separate from the engine harness. Automatic models may have a main DDE relay loom integrated to the engine harness. In any case, you can check that the relay is connected to plug 1 in this configuration. This will enable the ECU to control its own power.
DDE 5 main relay (Follow Wiseman’s Engineering Ltd’s instructions)
6hp transmission wiring
The 6hp26 has a mechanical shifter. Therefore, the only necessary electrical connections to the transmission are as follows:
– CAN high and CAN low to be connected to the engine
– Step-tronic signal (upshift and downshift)
– Terminal 15 (Ignition)
– Ground x2
– Terminal 30 (Permanent fused supply)
The 6hp28 is wired up in the same manner, however there may be an electronic shifter to add. The pinouts for the electronic shifter are below:
CAN – bus
In some cases you will need to wire up a can bus circuit, for example, when wiring up a 6hp transmission or other components.
CAN Hi wires should be connected together.
CAN Lo wires should be connected together.
One thing you must check, with all power turned off, the resistance between CAN Lo and CAN Hi should be 60 ohms. Quite often it will read 120 Ohms, in this case you should add a single 120 Ohm resistor from CAN Lo to CAN Hi. Since the CAN circuit is so short, it won’t really matter where you put this in the circuit.