Celica St205 Code 54 Issue - Not the Temp Sensor...

[guile]

Hi all

I've got the all too common Code 54 on my ST205 1994 jap import model which is putting the car in limp mode and currently driving me mad because it can't drive me anywhere else...

So far I have:

1. Unplugged the temp sensor switch and checked the wires on the body side, getting 12v across the wires. Is this normal, I just expected that the switch bridged a signal, not voltage?

2. Bridged the two sensor wires on the body side and therefore removed the sensor from the equation

3. Disconnected the charge pump and put 12v across the black and red wires, the pump ran instantly and made no bad noises (reconnected pump)

4. Checked continuity of the 30 amp CDS fuse which appears fine

5. Checked voltage across the switch on the relay and got 12v

6. Checked voltage across the coil on the relay and got nothing with the car on and running (temp sensor bridged)

7. Removed the relay outer casing and pushed the contacts together, the pump ran fine

I can't think of any else to check but it looks like the relay is not getting a signal to switch the pump on then tell the ecu its drawing power so it doesn't go in to limp mode.

I thought about wiring up the pump plug with the resistors (the mod people do when they replace the charge cooler with and intercooler). Just to see if I can stop it going in to limp mode. Then wire the pump to a switch from the Battery just so I can drive it somewhere to get it checked out. do you think that will work?

Any help and advice greatly appreciated thanks. I'll document the fix in case it helps someone else later down the track.

Ive attached a few photos:

- Ecu pin out diagram

- Wiring diagram including charge collar pump an temp sensor

- Wiring arrangement to include resistors at pump connector

Thanks to the original posters for the photos, hope I'm not breaking any copyrights...

IMG_6144.heic

[guile]

Hi all

I need to correct my previous post but I can't find the edit option...

wherever I said temp sensor I meant coolant level sensor on the charge cooler