Latham

Hey guys,
After some help with my rx8 2004. Just had an engine rebuild and it starts and runs but a few other issues have arisen. The thermo fans don’t kick in, the A/C clutch doesn’t engage, air bag and DSC/traction control light is on and the fuel level sender is reading high. As far as I’m aware they all worked before removing the engine and were not touched during the engine removal. (Also, mainly focused on fans, and I’ll move to the other faults later)

I’ve checked all of the fuses (engine bay and cabin) and the relays for the fans and ac clutch all work. When you bridge out the contacts for either the fans or ac clutch they engage and work correctly (including all three fan speeds) so the power side works correctly. When the engine is running I’m getting 13v from battery negative to wire B/L on the drawing which from my understanding is correct. (Fan 1 relay when engine is running) With the relay in I’m getting 13v on R/G wire but as soon as you disconnect the relays it drops down to 0v to negative. It looks like a high resistance joint to me but I’ve looked over all of the plugs and the wiring harness from the fuse box to the ecu/pcm. I’ve tried testing the continuity on the wire but didn’t get any results that made sense to me but that could be just me. I have some experience in heavy industry control (digital and analog 4-20mA) but minimal in auto electrical. So the drawing are a little bit different to what im use to so i could be testing the wrong pin etc. I’ve also gone around and made sure all of the ground on the car are making good continuity, ive heard that can cause some weird issues.
I’m currently back at work and can’t do any more testing till i get home.

My main concern is if all or most of these faults are related to a failure in the ecu, hoping not tho. The car has been sitting for 12months and moisture does like to do weird things to electronics.

So far i can only think of testing the voltage output at the ecu for the fans and more continuity checking of the cable. So any other ideas on how to fault find this would be great thanks.
I have also come across some posts about dsc light fixes that ill have to try to🤞

FYI: i have been using a obd2 port reader thing to monitor faults and also engine temperature. Don’t wanna cook a new engine hey hahaha🥵😂

Fan control

dannobre

iTrader: (3)

The R/G and L/W are grounds to the ECU that it uses to turn the relays on and off... so you shouldn't be looking for power there. They should be grounded when the ECU wants the relay on.... and no continuity to ground when they are off. B/L should have constant power....

If you have a high end ECU scanner it should allow you to trip activate all the relays through the ECU to test

Check the harness connections for the ECU and the engine grounds... they were disconnected when the motor was out for sure.

Main ECU/engine ground is on the top of the engine. Make sure the grounding strap near the starter is connected as well...

Latham

Thanks for your help, i ended up tracing out all the cables and they were all good. First time checking it, i had the plug upside down , definitely easier and more use to dealing with cables numbers but yeah.

I ended up buying a forscan OBDII port reader, best tools in the world $65 including postage plus $15 a year for the premium software. Ill have to make a forum about it sometime if someone hasn't already.
Once i got the car moving the fans started working which is weird, before it was getting up to 104c without doing anything and now stage one comes on at 97c . All of the other fault have been pretty much resolved by just doing the dash, steering full lock and the break pressing calibrations that have already been talked about in detail on rx8 forms. AC still not working but i think that a low gas issue tho and isn't important to getting it onto the road.

Hopefully my next post will be about the car running or a diy fan / fan controller for the oil coolers for under $100 AUD. Tested out the fan yesterday and it works pretty well. Definity a must have because the Australian version only ever had one oil cooler on all series 1, not sure about series 2.