Ott_outback Posted August 15, 2020 Share Posted August 15, 2020 Hi everyone, I am new to the Subaru community.I bought a 2011 outback it has been great but...It has left us stranded on the side of the road 4 times in the past year. Fuse # 12 blows while driving...car dies and will not restart, replace fuse #12 turn the key, pop just keep blowing fuses, starter doesn't activate, no fuel pump noise. (fuse #12 is integrated unit and automatic transmission). symptoms seem to point to a dead short but my local mechanics are unable to find anything.... The FSM shows fuse #12, 15 Amps, in the cabin fuse panel powers: my OB is not TurboA/C Control ModuleBody integrated unitLight control sensorTransmission Control ModuleEngine Control ModuleFuel pump relayIgnition coil No. 1 (turbo model) Ignition coil No. 2 (turbo model)Ignition coil No. 3 (turbo model)Ignition coil No. 4 (turbo model) To date the mechanic has replaced the fuel pump relay (the day I went to pick it up it blew fuse 12 several times....even when it was bumped up to a 30A) To potentially isolate the problem from the other sensors that fuse 12 services they isolated the ecm. They ran a dedicated fuse (15amp) to the ecm. The thought was is if that fuse blows we know it's the ecm $$. If fuse 12 blows then it's either a dead short on that circuit or 1 of the 2 sensors (light sensor and there is one on the transmission I think). It happened again but because we have the ecm on its own fused circuit the car cranked but would not catch. Good juice to battery did not think to listen for fuel pump. Floated it to mechanic and they discovered that fuse 12 was blown yet again! Put in a new fuse and it runs. Code that were present when car got to mechanic yesterday wereU0101 lost comm TCMABS C0044 CURRENT TCMC0057 ECM ELECTRICAL PARK BRAKEC0231 ECM FAILUREC262 TCM COMMC0221 PARK SWITCH LINE ABNORMAL Sorry this has been a long post but i wanted to post as much info as i could. I will be chasing down shorts from fuse 12 over the next few weeks, hope to find the issue. Testing the light load and the transmission sensor are on the work order as well as inspect the wire and fuel pump relay harness. any other ideas/ experiences that people may have that could assist me in narrowing my workload would be greatly appreciated. Link to comment Share on other sites More sharing options...
idosubaru Posted August 15, 2020 Share Posted August 15, 2020 These are so difficult. Is it possible to test continuity of each wire from that fuse? Need to look at the FSM wiring diagram for that. I would disconnect the light control sensor and AC control module and see if the car still is drivable. If so I’d drive it like that and see if it blows. But then you could get stranded again....which almost seems likely given the details you’ve given. I really hate to guess here because it needs to be diagnosed specifically. But those codes make it seem like the BIU or trans or engine harnesses. But it’s possible those codes were just artifacts from momentary spikes caused by the blowing fuse and not real codes. ***How often do you get codes - every time the fuse blows or just this time? 1, Rodent damage. I’ve seen chewed wires under seat carpeting that didn’t look like mice could get too. You can only find this by tracing each wire with a tester, unless the wires and damage are really easy to view. But then again - if it’s an inconsistent short you might not catch it. Two contributing factors I’ve seen: In urban areas - If car is parked in an area where mice and chipmunks are common in the parking this might be a clue. Or if the car has food crumbs in it from kids or pets which could attract mice. The chewed wiring I’ve seen were all parked in urban areas with chipmunks everywhere, I think they were running around while I worked on the vehicle, or parents with kids and years of food crumbs in the car. * ideally you trace each wire from the fuse and find which one is broken. Use the FSM wiring diagram to find the end of each wire that passes through the fuse. But if you have an intermittent short I’m not sure, electrical is one me my weaknesses but the few Link to comment Share on other sites More sharing options...
Ott_outback Posted August 16, 2020 Author Share Posted August 16, 2020 Thank you for the input. I am going to chase some of the wires over the next bit. Disabling the 2 sensors sounds like a great idea I will see if its functionally possibility. Previous to routing the power and fused the power to the ECM we have have not retrieved any codes, the car would be just dead. On the positive side i feel that since we are able to crank the engine that the ECM is good. Any results I will post. Link to comment Share on other sites More sharing options...
Rampage Posted August 18, 2020 Share Posted August 18, 2020 On 8/15/2020 at 7:13 AM, Ott_outback said: It happened again but because we have the ecm on its own fused circuit the car cranked but would not catch. That is because when fuse 12 blew the fuel pump relay coil did not have power to run the pump. Using the FSM, look up each item on your list powered by fuse 12. Two of the lines are FB31 and FB32 that feed different devices. Find the connector numbers. Example: The TCM has multiple connectors and you will see the power wire goes to Pins A18 and A19. For this one, scroll down a few pages and you will see pics of the connectors. Connector A is B54. When you look at Security, the Body Integrated Unit is at the bottom of that page. When you have the connector numbers, go to the Wiring Harness Sections and it will show you where those connectors are located. I would print those pages. You will be able to follow the harness from those connectors back to the fuse box looking for shorts to the body or brackets. Also look for places that are cut open or maybe squashed. You can unplug all of those connectors and see if the fuse blows when you turn the key on. If it does, then the short is in the harness somewhere. Since you gave the ECM it's own power source, when you are done, the ECM will have codes that you will have to clear. Link to comment Share on other sites More sharing options...
lmdew Posted August 18, 2020 Share Posted August 18, 2020 (edited) Load Pro is a great addition to your tool set. https://www.jbtools.com/electronic-specialties-180-loadpro-dynamic-test-leads-60-long/?gclid=Cj0KCQjw-O35BRDVARIsAJU5mQWgUyIsWhJ9Yw24LZ-S25irTvrKs7nYGBHoBLmyDLb2o3aUDOPGSEsaAnyFEALw_wcB Check it out on youtube. Edited August 18, 2020 by lmdew Link to comment Share on other sites More sharing options...
idosubaru Posted August 18, 2020 Share Posted August 18, 2020 2 hours ago, lmdew said: Load Pro is a great addition to your tool set. https://www.jbtools.com/electronic-specialties-180-loadpro-dynamic-test-leads-60-long/?gclid=Cj0KCQjw-O35BRDVARIsAJU5mQWgUyIsWhJ9Yw24LZ-S25irTvrKs7nYGBHoBLmyDLb2o3aUDOPGSEsaAnyFEALw_wcB Check it out on youtube. Great, thanks. I want to replace my homemade alligator clip set up. I don’t do enough electrical to know if the elaborate sets are over my head/uses or the simple tools wouldn’t offer much improvement. I’ll check this out when I have a real internet connection, thanks for the link and video. Link to comment Share on other sites More sharing options...
Rampage Posted August 18, 2020 Share Posted August 18, 2020 That is a handy tool at certain times. In his example of testing a 12v motor circuit, I would use a volt meter, neg. connected to a good ground and pos. to each terminal of the motor (one side at a time). Low or no voltage both sides bad power source. 12v both sides, bad ground. 12v one side, no voltage other side, open motor. Link to comment Share on other sites More sharing options...
lmdew Posted August 19, 2020 Share Posted August 19, 2020 As long as you load the circuit during the test that works. If you are just reading voltage your meter can lie to you. Link to comment Share on other sites More sharing options...
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