I'm sorry if the title is confusing - I'm not exactly sure how to pose this question/concern. I'm rewiring a 12 volt automotive engine control harness to be used stand-alone outside the original vehicle. Part of the process is to eliminate the rest of the original vehicle harness & unnecessary components of the relay & fuse box that are intertwined with the engine harness. The factory service manual gives me the following diagram (reduced to show only necessary fusing/relays for my application), but I'm concerned that it is oversimplified and may not show the necessary relay coil suppression to protect the ECM (engine control module). The "CPU" in the diagram is not the ECM I'm concerned about.
I had planned to use TE V23232-D0001-X001 relays for the throttle control motor, ECM relay, fuel pump relay, & starter relay. The coil resistance is 46ohm, and the relays have no built-in suppression.
For the ignition relay I planned to use a TE V23132-A2001-X30 (used on multiple BMW models). I cannot find exact specifications for this OEM model, other than seeing it listed as 130A and with the schematic printed on the relay housing. It appears to have a resistor in parallel with the coil. The general version of this relay has a coil resistance of 37ohm, with a resistor for coil suppression. The coil rating has a footnote indicating the ratings are "with resistor". The coil does read 37ohm across the terminals.
My questions, as general as they are:
What coil suppression method(s) should I use to protect the ECM considering I don't know if it has any built-in protection? Switching speed isn't a concern, but I'd prefer to get decent contact life from the relays.
If the ECM already has protection built in, does adding another layer cause complications?
If the V23132-A2001-X30 relay has a resistor built in, is any other suppression necessary, and what method would be used if so? The FSM schematic as shown has a series diode & resistor in parallel with the ignition relay coil, but this is not built in to the components I'm using and would have to be added if necessary.