2011 Volvo L90f " i-ecu reduced communication"

[zlssefi]

Hopefully the local volvo experts can chime in on this one..... i have been successfully working through the random issues and oversights that were plaguing this machine. Today i came across a head scratcher. I was diagnosing the rotating beacon light as it was not working. I powered up the light by itself and it works perfect. I chased the wires back to the panel behind the seat, where i found a rectangular plastic plug with a series of wires going through it.....unplugged
Perfect find!!!! Not. After plugging this plug in, not only does the rotating beacon not work, but now i also get " i-ecu reduced communication" as a message. With that unplugged i dont get the message. Ideas?? Error message is attached.

 

[funwithfuel]

Every connector has an address on it that corresponds to the socket on the PCB. If you could share what you plugged in, to where, we may be able to help. Additionally, have you checked power and ground at the beacon itself?

 

[zlssefi]

This is the plug i found disconnected. It is the center plug of a 3 plug bank directly behind the right console, mounted on the rear firewall of the cab. I found the strobe power and ground wires in that plug, powered them up and the beacon works as it should. I had no power or ground at the beacon itself which is why i started chasing wires.

 

[zlssefi]

The plug says " ca" on it and the middle socket says "lb".

 

[funwithfuel]

I'm guessing that's for an option that it's not equipped with. Aaron far as the beacon, I will try to provide a schematic tomorrow. Unfortunately my laptop has decided to take an unscheduled break

 

[zlssefi]

now that you mention it.....a plug saying ca wouldnt go into a socket saying lb.... the factory harness is there along with a factory rotating beacon and beacon switch. When switched on the icon illuminates on the dash but nothing else. Maybe theres another box, or junction of some sort removed by the previous owner....?

 

[funwithfuel]

As promised

 

[zlssefi]

Thank you! On the right hand side of the schematic what does 31cr stand for?

 

[funwithfuel]

31 = ground
30= battery hot
15= ignition hot
The CR is the location address. Where on the machine the wire is physically grounded. Don't have that info in front of me. I believe it's in the Left rear behind the PCB up against the back panel

 

[zlssefi]

Looking over this schematic, what function does the instrument ecu play when it comes to the rotating beacon? It looks like one of the wires from the switch, terminates at the i-ecu. Am i reading that correct? I have an identical 90f which doesnt have this issue, im going to look behind the seat of that one to see where the plug leading to the roof top is plugged in.

 

[funwithfuel]

Connector DD cavity 12. It's right there in the schematic. The lead that runs off to the IECU is just the indicator that tells you the beacon is lit or should be lit.

 

[funwithfuel]

If you remove the ductwork and glove box from the right side of the cab. You'll also have to pull the HVAC box out and rest it on the step, You'll see the cab harness. The harness is poorly protected from moisture and lays right on the floor. I have experienced problems in that area, sometimes powering heated mirrors, sometimes back-up camera. If you start pulling purple wire 3019, tug gently every couple inches, don't be surprised if it suddenly gives way. Track it back to the splice that corroded away. It should be the same color but change numbers to 3018. The wire is numbered every foot or so. Good luck

 

[zlssefi]

Excellent advice. Ill dig some more tomorrow.

 

[zlssefi]

Well....problem solved. For whatever reason this machine had two aux light harnesses run from the fuse panel area up the right rear cab corner and up above the headliner. It had two plugs labeled "ca" right near the socket bank. The opposite end of the ca plug which was plugged in, had no connection to the ayx lights and rotary beacon. I removed the secondary harness and attached the proper wires to the beacon and work lights. Everything is now 100 percent functional.