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2006 Subaru Forester SBF5 Fuse Issue

Home Forums Stay Dirty Lounge Service and Repair Questions Answered Here 2006 Subaru Forester SBF5 Fuse Issue

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  • #988825
    Thomas CaninoThomas Canino

      The morning of the incident I started the car to let it warm up, since it was about 25* F/-3.9*C. About ten minutes later I was going to leave for work and realised that I had forgot my phone. I was going to just leave it running and get my phone, but my awesome wife brought it to me. At that moment the car shut off. I thought I stalled it by letting the clutch out with the parking brake on. Attempt to crank it, and nothing but warning lights. A few weeks prior the starter didn’t engage correctly so I thought it was the problem. Conveniently our house is on a hill so I figured I would roll it out of the driveway, let the clutch out and be on my way.
      First thing I noticed was the engine didn’t start with the ignition on and the drivetrain turning it, and it didn’t sound right. Difficult to explain, but like it was loping. The second thing I noticed was the check engine light was flashing. Luckily our street is in a neighborhood, so I could coast the not running car onto a side street.
      Later the day, I began searching the interwebs which lead to this forum. First thing I found was a blown SBF 5 fuse. This is where I will admit making a terrible decision. Since the car was broken down away from the house, and I didn’t have another fuse, I jumped the fuse with a section of wire with alligator clips on both ends. The car started right up and ran long enough to back out of where it coasted to earlier that morning, about 30 seconds. I was going to drive up the street and into my driveway, but it began fumbling like it was running out of gas. It idled for a few seconds and then stalled. I pulled the jumper wire off and it was hot. The wire had nearly been melted off one end of the alligator clip. I know this was basically the same as sticking a fork in an electric outlet.
      I was able to enlist the help of my neighbors to tow the car up the street. Once in the driveway I began investigating the extent of the damage I inflicted.
      The car would not crank or start. With ignition in Run, the cooling fan on right hand side off the radiator would run continuously and the check engine light did not illuminate. I was able to find the schematics online, printed them out, and went to work trouble shooting. The path of power from SBF 5 goes to the main relay. It was also the first component damaged by me.
      Replace relay with OEM ordered from a local Subaru dealership, put the correct 30 amp fuse in SBF 5, turn on ignition, and the check engine light begins to flash rapidly along with the cooling fan cycling on and off about every second before blowing the fuse.
      I have traced every path of power supplied by SBF 5 and everything checks out as far as power flow and continuity. After that, I traced everything supplied power by the main relay. Again, everything checked out. No other components showed signs of damage, no melted connections, no indication of a dead short in the wiring, nothing. Even with every component unplugged from that circuit, the same behavior of the flashing CEL and cycling of the fan occurred.
      After searching through threads of blown SBF 5 fuses, and most lead to problems with the fuel pump. I have tested everything concerning the pump, even tested the fuel pump relay, the power supply and continuity of the harness and associated sensors, and have not found the problem.
      I’m asking if anyone has had a similar problem or where to look next?

      • This topic was modified 3 years, 2 months ago by Thomas CaninoThomas Canino.
    Viewing 6 replies - 1 through 6 (of 6 total)
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    • #988842
      Nightflyr *Richard Kirshy

        ” I found was a blown SBF 5 fuse ”
        There is your first issue.
        Something that is fed by that fuse is shorted.
        It may be a component or in the wiring.
        You state that you replaced the fuse.
        I assume that it has not failed again? but your CEL is still flashing and still have a fan issue.

        First thing I would check is for codes from the ECM, provided you can still talk to it.
        Next might try unplugging the fuel pump and see what happens with ignition on.
        After that start unplugging one sensor at a time connected to SBF5 fuse and see where that leads.
        If after disconnecting all circuits from SBF5 fuse you still have issue, chances are you have a wiring issue.
        Could start with the basics and check the 5V ref and see if there is, then check the CAN buss to see if that is alive and talking.

        Thomas CaninoThomas Canino

          Thanks for your reply.
          Yes, I replaced the fuse and it blew again. With the correct fuse and new main relay installed is when the CEL flashed and the fan cycled.
          I haven’t tried to read codes since SBF 5 is the battery or constant power supply to the ECM. As stated, the fuse blows almost instantly so I don’t want to damage the ECM. For test purposes I am using a 30 amp circuit breaker in the place of the fuse.
          I have unplugged everything in the direct power supply from SBF 5. I have also unplugged the harness to the fuel pump after testing it for functionality, and unplugged all sensors and components powered by the affected side of the main relay.
          I agree with you that there is a wiring issue somewhere, just a matter of finding it. I will check out the CAN bus communication and 5V ref that the rest of the sensors are on.

          Nightflyr *Richard Kirshy

            May want to try disconnecting the ECM and see if the fuse still blows.
            You may not like it, but it is possible the ECM is shorted

            Thomas CaninoThomas Canino

              That is both my concern and conclusion at the moment. I still have some testing to do in order to confirm or rule it out.

              Thomas CaninoThomas Canino

                The short has been found! Believe it or not, when I bypassed SBF 5 power was sent through four relays, fuel pump, main, A/F O2, and electronic throttle control, along with two terminals of the ECM, out terminal 4 of the main relay and to the power supply for the pressure control solenoid and the drain valve of the evap canister.

                Although I did not find the actual short or wires burned together, I did find evidence of where the wire was heated and discolored as it came through connector R57. It had also been hot enough to melt some of the sound deadening material before the harness went into a grommet and out the floor. The reason I couldn’t see the actual short is because that section of the harness is routed above the gas tank, then goes to the evap canister. I cut the wire at R57 and made sure it wouldn’t contact anything and disconnected the pressure control solenoid and drain valve.

                Nightflyr *Richard Kirshy

                  Glad to hear you tracked it down.

                Viewing 6 replies - 1 through 6 (of 6 total)
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