Celica St205 Code 54 Issue - Not the Coolant Level 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 coolant level 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 (coolant level 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...

 

[guile]

because I can only add 3 photos at a time...

 

[1fstgts]

I would open up the ECU and see if you have the leaky cap problem. Both of my ST205 ECUs that I had for motor swaps into my 4th gens had this issue. The engine started doing all kinds of strange things.

 

[guile]

thanks mate, really appreciate the quick response...

that's also where I'm at, therefore I don't think wiring up pump connector will be a temp fix for the issue...

I'll get on dr google to find out how to access the ecu and take a look...

I'm also getting an intermittent igniter fault code and have changed the igniter and coil but the code is still intermittent. what other errors where you getting with the faulty ecu out interest please?

also did you repair or replace your ecu?

 

[1fstgts]

Getting other random codes kinda reinforces that.

I repaired it myself. But Im also very fluent with electronics and soldering, etc.

 

[underscore]

I'm not sure if the 205 is the same, but with the 185 ECU the caps that tend to leak first are part of the CEL circuit. So it makes sense that it'd start giving you odd codes like this. They're pretty easy to pull and check, I think for all Celica's it's 3 10mm bolts holding it on the trans tunnel behind the footwell carpet.

 

[guile]

thanks again everyone, I managed to get time at the weekend and pull my ecu...

looks like capacitor c895 is leaking so I'm hoping that's the problem, fingers crossed...

I had a pretty good look around and the rest appeared ok. I'd get them all replaced but I just want to get the car on the road asap so i might do all the others as a preventative measure later on...

I just really hope that fixes it, I'll report back once I know...

 

[guile]

and for anyone else future reference I managed to get hold of these photos online which some else might find useful for capacitor ratings...

 

[guile]

does anyone know if there is an equivalent efi relay for this part number please as apparently its discontinued...

 

[1fstgts]

Make sure you replace them with a quality capacitor. Nichicon is probably the best.

 

[1fstgts]

Also make sure whoever does the repair cleans the board off of all that black stuff. Otherwise it will continue to eat at the traces as it's corrosive.

 

[93celicaconv]

Toyota P/N 85910-20040 does not appear to have been used in any North American Toyota vehicle. It was used on the Japan Celica ST205 (which is the case here) and on the following vehicles:

- Japan
- Celica
- ST202 (3S-FE & 3S-GE)
- ST203 (3S-FE)
- ST205 (3S-GTE)
- Carina ED
- ST200 (4S-FE)
- ST201 (4S-FE)
- ST202 (3S-FE & 3S-GE)
- ST203 (3S-FE)
- ST205 (3S-GE)
- Corona EXIV
- ST200 (4S-FE)
- ST201 (4S-FE)
- ST202 (3S-FE & 3S-GE)
- ST203 (3S-FE)
- ST205 (3S-GE)
- Curren
- ST206 (3S-FE & 3S-GE)
- ST207 (3S-FE)
- ST208 (4S-FE)

Given the wide use of the COR in Japan, I looked up the part number at Amayama.com, but unfortunately they show it as being discontinued.

In looking at your wiring diagram for the COR you have, I see that the 5th Gen Celicas used a COR that was very similar to the one shown in your diagram. I have a diagram view of the USDM ST184 C9 COR attached also, which is Toyota Part No. 85910-12010. If you compare what I attached as the COR against your wiring diagram, you will see the USDM version has another element inside the COR on terminal 4. I don't know how that affects the use of the COR, but the other terminals are identical and the terminal numbers align across both COR's. Getting the USDM COR would be relatively easy, as any 1990-1993 Celica in a salvage yard would have one. But you would have to dig into this slight difference to understand if that would not affect your application, or if it would not work in your application. Best I can help you out with on this part of your thread topic.

 

[zaluss]

Not sure if this helps but I struggled trying to resolve this Code 54 issue and even swapped to another known good ST205 ECU with the same problem. Tried all the various relays, etc. I ended up using a Gen3 MR2 ECU which doesn't have the coolant level sensor problem and it's been good ever since.

I think the mapping is slightly different but works great.

 

[guile]

Make sure you replace them with a quality capacitor. Nichicon is probably the best.

unfortunately I could only buy from the local Jaycar in Australia without waiting 3 weeks for delivery and really wanted it on the road for xmas, fingers crossed the cheap one works...

I'll check when I get it back to make sure they cleaned to board, if not do you know what I can clean it with please? gin and cue tip...

I did order about 4 times as many capacitors as I think I need from the uk so if anything else goes pear shaped I'll get them all replaced with these, Panasonic ones I think...

 

[guile]

Getting the USDM COR would be relatively easy, as any 1990-1993 Celica in a salvage yard would have one. But you would have to dig into this slight difference to understand if that would not affect your application, or if it would not work in your application. Best I can help you out with on this part of your thread topic.

thanks mate, I only want to replace it because one of the tabs has broken off (30 year old plastic is very brittle I'm finding)...

I think I'll leave it as is at the risk of stuffing something up using the wrong relay...

 

[guile]

Not sure if this helps but I struggled trying to resolve this Code 54 issue and even swapped to another known good ST205 ECU with the same problem. Tried all the various relays, etc. I ended up using a Gen3 MR2 ECU which doesn't have the coolant level sensor problem and it's been good ever since.

I think the mapping is slightly different but works great.

I have a feeling it will be too good to be true if replacing the cap fixes it, I'm very hopeful though...

any ideas were i'd get a gen3 mr2 ecu please, do they have a different part number?

 

[underscore]

I have a diagram view of the USDM ST184 C9 COR attached also, which is Toyota Part No. 85910-12010.

I tried one of those in my 185 RC and when the key was turned to ON the starter would engage. I'm not entirely sure how that happened but something was feeding power incorrectly. It didn't harm anything but it's something to watch for. The 185 relay 85910-30050 is still available, it was pretty widely used including in all 4th gens (not just the 165) and might match the 205 circuitry better.

 

[zaluss]

Not sure if this helps but I struggled trying to resolve this Code 54 issue and even swapped to another known good ST205 ECU with the same problem. Tried all the various relays, etc. I ended up using a Gen3 MR2 ECU which doesn't have the coolant level sensor problem and it's been good ever since.

I think the mapping is slightly different but works great.

I have a feeling it will be too good to be true if replacing the cap fixes it, I'm very hopeful though...

any ideas were i'd get a gen3 mr2 ecu please, do they have a different part number?

Yes different part number 89661-17460. I would try the MR2OC facebook group or ebay.

 

[guile]

I'm very pleased to say that replacing the capacitor looks like it fixed the issue so I'm off to try and get it registered this Friday, YAY!

I treated myself to a very expensive new old grille with a very rusty TRD badge. I'm hoping to gently remove with a dremmel cut off wheel while trying not to damage the plastic...

a massive thanks to everyone for advice and guiding me in the right direction, this forum rocks!