Evo 4 to 8 swap - Electrical problems

[Dvolution]

Swapped an Evo 8 engine in my 4, using a 6 ECU, and I am having a few electrical problems. I have checked that all connectors are tight. I will list the issues I am experiencing, please help with any that you can.

1. CEL on, cannot check because EvoScan says Battery Voltage is 1.873v when I have a charger on it.
2. AYC light on.
3. No odometer.
4. No blower motor.
5. Rad fan always on when engine on.
6. No interior light.

 

[fq-craigus]

Swapped an Evo 8 engine in my 4, using a 6 ECU, and I am having a few electrical problems. I have checked that all connectors are tight. I will list the issues I am experiencing, please help with any that you can.

1. CEL on, cannot check because EvoScan says Battery Voltage is 1.873v when I have a charger on it.
2. AYC light on.
3. No odometer.
4. No blower motor.
5. Rad fan always on when engine on.
6. No interior light.

Ayc will need bleeding as you have messed with transfer box fluids. Firstly check fuses as none of these issues seem common faults to me. Is any of the clocks working or is it just the mileage that's not working.

 

[RsvRob]

Transfer box on a 4 doesn't run the AYC. Only 7-9 do. 4-6 only have AYC on rear diff.
Sometimes you have to cut an ecu wire because the alternator doesn't charge. This may be related to your battery issue and evoscan.
You could try flashing the codes out via OBD.
Oh and once a battery drops below 9v it's normally ****ed. Even with a charger connected. Get a multi meter on it to check. Then replace if needed.

 

[Dvolution]

Transfer box on a 4 doesn't run the AYC. Only 7-9 do. 4-6 only have AYC on rear diff.
Sometimes you have to cut an ecu wire because the alternator doesn't charge. This may be related to your battery issue and evoscan.
You could try flashing the codes out via OBD.
Oh and once a battery drops below 9v it's normally ****ed. Even with a charger connected. Get a multi meter on it to check. Then replace if needed.

I remember that some people needed to do that when converting their 4 ECU to a 6, but I did that conversion a year ago and had no such trouble.

I wasn't having any trouble with the battery at all, it started the car after sitting for 2 weeks without a charger. I only threw the charger on the battery after EvoScan told me voltage was low. It starts strong without a charger attached yet EvoScan still continues to misread the voltage.

 

[Dvolution]

Battery was 5 years old, replaced just because.

I fixed the CEL and AYC light, it was just a TPS adjustment issue. Took it out for a spin and the odometer, RPM gauge, and blower motor intermittently work; more evidence of a ground problem that I am still confused about.

All of the grounds I had removed and replaced are clean and tight, but after checking the wiring diagrams, my ground issues seem related to grounds inside the vehicle that I have not even touched. This must mean the problem is in the wiring harness/loom.

I would like to test the main loom/harness for broken wires but I have no idea where to begin. Can anyone offer any advice? Electrical diagnosis isn't my specialty.

 

[Dvolution]

All of the grounds have zero resistance and are properly secured.

 

[raph]

Ground strap on the firewall in engine bay? And the battery isnt touching the bonnet?

 

[Dvolution]

Ground strap on the firewall in engine bay? And the battery isnt touching the bonnet?

That was the first one I checked as the previous owner had it routed the wrong way. This guy had two ground straps from the intake manifold to the firewall and one from the valve cover to throttle cable bracket. I re-routed it so there is a nice string from firewall, to manifold, to throttle bracket, to valve cover. Zero resistance at all connections.

So I have actually improved the earthing system from it's previous state. When I checked all the grounds I made sure to not only test the bolt/nut but the terminals as well as probing the wire a little bit behind the terminal.

The battery has about 2 inches of clearance from the hood.

Another thing I noticed: I get a battery light when driving at higher RPM, goes away when I return to idle.

 

[Dvolution]

Just a fuse. OEM 100A was a semi-circle bent wire and it broke at the bottom where I couldn't see.

 

[raph]

Ah ok thanks for posting up what solved the issue