Imo000

Is there a way to bypass or check the catalytic converter temperature sensors on a Japaneese S4? The one I'm working on decided to flash the "Cat Hot" warning. This happend after some TT and MM work. The snesors were in very bad shape when I pulled them and wouldn't be supprised if they didn't make it. The engien is running perfect and I'm certain it's a false code. However since, as far as I know, only the Japaneese spec cars had this, I wouldn't mind offering the owner the option to just dissable them.


Anyone has any suggestions on how to do this?

Bill Ball

What year?

I don't know exactly how this works, but...

For 1990+, fuse 43 appears to provide switched power to it. What happens if you pull fuse 43?

Prior to that it is not fused and gets power from another timer relay.

davek9

Just thinking out loud here.. don’t most of these sensors fail to indicate a fault, so if you disconnect it that won’t help. You may be able to fool it by placing a resistor of some ohm value (?) across the sensor terminals.

Imo000

It's an '89. I'll see what that fuse does. I'n not yet sure how they operate either.

Bill Ball

It's not fused in 89 according to the wiring diagrams. The catalytic converter switching units communicate with each other and with the dash via yellow wires. The units are located in the center console under the radio. You could try clipping those. It looks like that should disable it.

The fuse is only shown in this circuit in 90+. It's called the phone fuse (43), but the wiring diagram shows it providing power to the the converter sensor circuit.

928Myles

The wires to my cat sensors were disonnected by some PO. I got the odd 'cat temp' warning until I made sure the wires were properly insulated where they were cut. No more messages. I think this would indicate that they trigger the warning when grounded.
The advise I recieved was that they were not an essential item so I did not attempt to reconnect them.

Mine is a 1990 ex Japan car.

Myles

Imo000

Thanks guys, the owner agrees to just dissable them too. What is the simplest/easiest way to get to this yellow wire?

Bill Ball

Imo: I've never seen one of these but according to the wiring diagram, the control boxes are under the radio. One of the alarm components is down there as well. So, it might be a bit confusing, but if you have the wiring diagram, you should be able to figure out which connectors down there matches the wire color pattern. Heck, maybe just pulling the plugs on the units may disable it.

Imo000

Thanks Bill, I'll see if I can find the wiring diagram for these cars.

Bill Ball

It's in the regular wiring diagram set. Here, this might help. I think outside of the immediate area of these control units you'd have a hard time finding the wires in the harness. Oh, you could find it up at the instrument panel, but that's more of a pain.

Imo000

That looks simpel enough, thanks. You don't happen top have the part number for these units?