Fueltech Wideband wiring - Star Earthing conflict

I am planning out a wiring job for a Fueltech FT600 with dual wideband modules.

The modules each have dual grounding pins that specifically say that one must go to battery and the other must go to the engine block.

This car has the battery in the rear of the car and these instructions go against my star earth design (using only engine block).

anyone have any experience with these modules?

Should i run a dedicated ground wire from battery?

My battery ground runs a 00AWG cable to the front of the car where it bolted through the body before bolting to the engine block (this becomes my chassis ground and engine ground at the same time)

My ECU grounds are all star earthed on the engine block

Black/White 10 Chassis/Engine Power Ground Engine ground (head/block) Do not connect it directly to the battery negative.

Black 11 Battery’s Negative Connected directly to the battery negative with no splices. Do not connectec this wire to the chassis engine block

G'day Anthony.

What I think will be going on there is that the BLACK/WHITE wire that connects to the engine block will be the power ground that passes the larger O2 sensor heater current, and the BLACK one connecting to the battery negative will be the units sensor ground level.

I'd reach out to fuel-tech for clarification, as if that is the case, you should be fine to connect the BLACK wire to one of your ECU's sensor ground pins, so they are sharing that ground level.

If they're not keen on releasing the details, all you can really do if follow their instructions, and just be aware that that is the way things are wired, so if you see any problems you'll know where to look.

I did find this in the manual, it sounds like your theory is correct Zac.

What would you recommend in this case?

Am i going to be ok grounding my ecu sensor ground and power ground to the same point on the engine block?

Black wire - Battery’s negative

This wire is responsible for signal ground to the ECU so, it must be connected straight to the battery’s negative terminal, with no seams. Under no circumstances, should this wire be connected to the vehicle chassis or split with the ECU black/white wire (power ground). This will cause electromagnetic interference and other problems hard to diagnose and solve.

Black/White wire – power ground

These are the ECU power ground wires. They must be connected to the engine block or head in a place with a good electrical contact. The same shield that goes from the chassis to the battery’s negative terminal is a good contact point. 37

The three power grounds (24 and 16-way connectors) must have permanent contact with the engine block/head, never being connected to switches, car alarms or others. To turn a FuelTech ECU off, the red wire should be switched on and off.

Power ground to ignition modules (SparkPRO, etc.), Peak and Hold drivers, relays and other accessories, must be connected to the same point, at the engine block/head.

A good test to check if the power grounds are with good connection is, using a tester, to measure the resistance between the battery’s negative terminal and the chassis ground. Connect the red probe on the chassis point that the shield is connected and the black probe on the battery’s negative. With the tester on the 200ohms range, the resistance measured must be below 0.2 Ohms.

Remember to touch both probes to check its resistance. This reading must be subtracted from the first reading to found the correct value.