RoGiSiK

Greetings good people

I recently got RX8 from my wife for my birthday, it was a great supprise for me, but after few days it was even greater supprise when i got to know my RX8, it is a mess...electronic mess to be precisse...
Mazda is grey 2005. 170kw, decat, right hand drive converted to left hand drive. Engine is ok, it runs great, starts hot and cold no problem, but it has Check Engine, ABS, Airbag and TCS lights on, and tachometer and speed droping to 0 and jumps right back from time to time...my goal is to bring this car to its original shine, but i need some help, because no one in my country knows how to solve my problems. .

NotAPreppie

You bought a can of worms that somebody else opened.

It sounds like they messed up the electrical wiring in a bad way.

The inconsistent tach/speed are probably due to a loose ground wire OR damaged CAN bus wire.

RoGiSiK

It was a supprise gift, so i didnt have any part in it.

Today i tried replacing instrument cluster with another from junk yard, but tha problem was the same, then i tryied to pull 2 direct separate CAN wires from ECU to instrument cluster separating the original wiring, but the problem was still there... grounding will be my next step.

And i forgot, DSC OFF switch seems to not working, presing it holding it or so, nothing happens, no DSC OFF light...

Loki

iTrader: (1)

What is the check engine code?
The gauges dropping to zero sounds like loose battery cables or (less likely) other electrical connection problems.

TCS, ABS and steering lights all come on after you disconnect the battery, so that fits.
The DSC OFF function may not work while TCS is in an error state.

One step at a time, let's get the codes. It starts warm, so that's a good sign..

RoGiSiK

Steering light is not lit, and battery is 2 months old and tight.
Tomorow ill go to some guy to read ABS codes...airbag is blinking in pattern 23 (2 blinks than 3).

RoGiSiK

Steering light is not lit, battery is 2 months old and tight...
tomorow ill go to some guy to check ABS codes. I tryed ECU reset, it was successful but after DSC calibration DSC OFF light went off but other 2 stays ( ABS and TCS)...

RoGiSiK

RoGiSiK

I posted some images with codes and dash, but must wait approval...

Loki

iTrader: (1)

Hmm sounds like a loose electrical connection nevertheless.
With car on and stationary, try to wiggle the wiring harness in various places to see if you can make the gauges drop.

It's also possible they're dropping because the ECU is losing power momentarily, so try around there too.

She bought you an exciting project!

RoGiSiK

Today i went to some guy and checked all codes with Mazda V41.50. Every system (ABS,TCS,EPS,IC,RKE,PCM) has code U1900...

Here are all the codes:

ABS/TCS
U1900
C1155

EPS
U1900

IC
U1900

RKE
U1900

PCM
P0037 (this rx is decat)
U0073

And Torque Pro readed two more
U0100
P0763

After clearing the codes,ABS light went off
U1900 stays for EPS,and after few minutes ABS light come on again which i gues is because of a faulty sensor.

Loki

iTrader: (1)

All these codes point to connectivity between modules. Either somebody used incompatible modules (such as if they put an ABS module with DSC into an automatic car without DSC), or the wires are poorly connected. That last P0763 points to this car being an automatic, which makes this scenario more likely. If it's a manual, it sure thinks its an automatic, so maybe they used an automatic ECU in a manual, somehow. It's probably worth plugging your VIN into Mazda's website or Carfax or similar service, to see what it's supposed to be.

P0037 should still not happen, as the O2 sensor should still be installed in the decat pipe.

NotAPreppie

U1900 and U0073 are both CAN communication error codes. Either the wire harness or harness connectors are damaged or the modules were swapped at some point and nobody bothered to reprogram the ECU to accept them. If these codes don't come back, then it's probably an old stored code from when the previous owner was screwing around. If they do come back after a while, start checking your wiring harnesses and connectors.

ABS/TCS C1155 is an error for the left front wheel speed sensor failed or disconnected (open circuit).
DTC C1145, C1155, C1165, C1175

P0037 means that the rear O2 sensor is bad, not present, or not connected. The presence of the cat has nothing to do with it. If you want that error to go away, put the rear O2 back in and connect it up.

RoGiSiK

Hmmmm...is there any way to find out which module does not belong in this car?

As you metioned before i noticed something strange in wireing harness before, the day i received this car it has error for clutch switch, than i checked under the steering wheel and there was none...so i got that switch from a junk yard put that switch on its place but there were not any connector for it, so than i found electrical schematic of RX8 an traced that switch to the ECU but on that pin on the connector there wasnt any wire (it should be purple). Furder studying the electrical scheme i figured, on the automatic transsmision there is no clutch switch and that pin with puprle wire is blank as mine was. I was confused, never the less i added one new wire from that switch to that blank pin on the ECU and error was gone, and even engine idle was much better. So my conclussion is that in my car is w.harness from automatic t. version...but studing this electrical schematic i canot find any major differencess betwen AT and MT, i mean on major systems like CAN bus or so.

I checked VIN number as you suggested, but i can barelly find anything about this car ..i tryed multiple sites and only two of them showed me, that number is for RX8, 2005, 230 HP and 6 speed MANUAL. Thats all..every other showed error in number...

As the instrument cluster concern, yesterday i cut factory CAN lines from wire harrnes in front of the IC connector and pulled 2 new separate wires directly to ECU, and connected them on pins for CAN bus, everything worked but again problems with tacho and speed are still present. So conclusion was, CAN wiring is good. One more thing is when i read RPMs and speed over OBD2 thera are no interupts like on IC...

Loki

iTrader: (1)

Hey that's good troubleshooting!

If you post up the module part numbers here for the ECU and ABS module we can help identify what doesn't belong.

So the VIN is for an RHD manual car, but it has the harness from an automatic car (probably LHD) ?

​​​​​May want to start shopping for a manual LHD wiring harness..

NotAPreppie

I can't tell from your description but make sure that your two new CAN bus wires are twisted together. CAN is a twisted-pair physical topology (like Ethernet) where the wires carry the same but opposite charge from each other. Doing this reduces interference into the signaling and caused by the signaling.

If the two wires of the pair aren't twisted, you may get unpredictable results. The easiest way to get twisted pair is a long Ethernet patch cable. It's nice and stranded so it won't work harden and break just from vibration nearly as easily as solid wire (typically installer wire that comes from a spool or a box).

RoGiSiK

Thats correct, i used twisted pair...but test was unsuccess, because problem was still there...

Ok, next thing ill collect all numbers from modules and ill post them here...

The car was deffinitly RHD because there are number of things that pointed on that, for example, right seat is full electric and left is not its manual, safety belt if not plugged in on the right side and no one is in the seat is beeping, even central console is opening from right to left, IC is mirrored from LHD, side mirrors are defferent angle, left side cant adjust so far left (you see half of a car in it) and windshield bottle has only one bolt, there is no hole for other... And i found hidden service book under the seat from the first 3 years of the cars life and it was serviced in England.

​