R/H Cat Temperature ECU Wiring Problem (F355 5.2)

Gents, as part of my effort to convert the F355 1994 2.7 wiring diagrams into 5.2 diagrams, I not only discovered some dodgy wiring in my instrument binnacle to stop the CEL and SDL illuminating, I think I'm missing the engine bay wiring harness from the right hand cat temperature ECU to the Motronic engine ECU (I have a R/H cat temperature ECU with nothing plugged into the upper connection). Or...possibly another variation... the plug going to the exhaust bypass temperature ECU is the one with the missing harness (and plugged into the wrong socket). Australian cars have 3 temperature ECUs like the USA cars.

Would anyone know where the wiring coming from the R/H cat temperature ECU goes into the harnesses in the engine bay? In the diagram below, it shows the harnesses I have at the moment.. and possible variations. One set of harnesses on the right hand side goes slightly aft to the rear bumper, then curves back over the wheel arch. This includes the secondary fan motor wiring and the wiring for the solenoids. Another set of wiring includes the R/H O2 sensors and one temperature ECU plug (not sure which ECU it belongs to). Both sets look like they have been tampered with (or damaged and repaired).

Wiring possibilities

If I can figure out where the harness has been cut off, I can probably fabricate a new section of harness and splice it back on. My cats have been gutted and I intend fitting new cats or recoring the original ones.

Thanks for any insight.

Cheers
Ian

P.S. The left cat temperature ECU has wiring, but is open circuit (I think somewhere around the firewall). My Motronics engine ECU is on the right hand side of the car (I don't know if this is the same for USA/Europe cars?)

 

Brilliant! Thanks Mitchell. I'll check now...

 

All input helps, thanks, Paul

Unfortunately, there is no sign of a fourth harness in that O2 harness group. At the point where the harnesses merge (10 or so inches from the plug), it looks original. It's like one of the previous owners has used the wrong harness. i.e. one without a exhaust bypass temp circuit, then converted the wiring to bypass wiring. They probably deemed that the cat temp ECUs were not required because there is no catalytic material in the cats. With the dashboard wiring previously "modified", it wouldn't have generated a CEL.

Continuity checks of the harness seem to indicate that the plug I have corresponds to the bypass temperature circuit, but the wires may be swapped with splices close to the Motronics end. I would probably have to check this at the next engine out. I'll either have to replace the whole engine harness (ouch) or add an extra small harness or two (from the Motronics to the cat temp ECUs).

Cheers,

 

Here's a pic of the harness where it merges...

O2 Sensor/Cat TCU Harness Junction

The thermofit/shrinkwrap looks original and I'd say the O2 sensor plugs were fitted after the thermofitting (I don't think thermofit would be big enough to take the plugs and be able to shrink to the loom size.

Cheers