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JPX

96 Legacy 2.2 electrical shutdown when driving (cranks, won't start, no warning lights will come on)

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Hello all - 1996 Legacy L sedan with 218,000 miles and an IN-CAR head gasket job completed last month (oh my back! :blink: ). Car has been running through 2 tanks of gas with no problems.

 

During mile 38 on 40 mile freeway drive at 2:30am, the electrical system on the car suddenly shut down and I coasted the car to a stop on the road shoulder.

 

Hazard blinkers were functional, along with interior lights and power locks.  High beams would turn on brightly, but since the headlights/parking lights are tied to the ignition, these were not operable.

 

I could only conduct a few quick checks roadside:

- bang on fuel pump - directly since I took the access plate in the trunk off. Done this routine before on several cars <_< .

- check tight battery connections - recently cleaned during head gasket replacement last month - this was fine.

- timing belt intact

- all fuses in engine bay and under dash continuity checked ok

- starter cranked the engine, but the engine simply would not start

 

Then the car got towed home the last 2 miles of my intended drive.   Fortunately a flatbed tow truck showed up in 10 min via AAA  and I was home only 30min after the mess.

 - I had to help the tow truck driver get into the shifter plate to manually override the shifter interlock so he could put the car in neutral.   With the key-On position, the solenoid for the shifter interlock would not move......no elec power going to it.

 

I have since conducted these tests:

- battery voltage in good standing is 12.65V

- alternator removed, tested and passed

- ohmed out coil pack - pass. No burn throughs.

- grounds confirmed good - removed and cleaned again anyway

- checked all fuses and the main fusible link with ohm-meter - none blown

- pulled and checked all engine connector harnesses (bell housing, MAF, igniter, ECM under the passenger floor).

- checked continuity on all positions of the ignition switch - pass.  Getting 12V to the backside of the switch by probing the solder points.

- pulled and cleaned crank and cam position sensors - not much interesting there.

 

Here's the fun part :

none of the warning lights on the dash will light in the Key-On position - this is what I find very disturbing. :( .

- Starter/solenoid happily cranks the engine, but won't start. I have experienced bad start contacts before - this isn't the what is going on here)

- cannot read ANY CEL codes because there is no power to the ECU when Key-On

- fuel pump will not turn (can't hear a click from the pump relay anyway)

- shifter interlock still not operable because of no power going to its solenoid - tied to ignition key-on.

 

I could start changing out crank/cam position sensors, coolant temp sensor, MAF, etc.....but none of these single point items can easily explain why the entire power circuit is not operating. Even if the ECU died, I should still get direct power up to it.
 

In looking at the wiring diagrams, I am thinking the ignition relay (the brown, really-hard-to-reach-one under the dash) might have conked out.   This is the only way I can think of that I can still crank the starter, but hot have any electrical controls that drive the fuel pump, the warning lights, and the ECU.

 

I'm going to attempt to get at the ignition relay today to pull and test it - that will take me all morning and lots of scrapes on arms.

 

Any other suggestions are most welcome as I try to figure this out.

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Could be a burned out ignition switch.

Does the radio work in key On? Does it work in key Acc?

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You seem to have a good grasp of the trouble and where to look for it. Things like engine sensors are not the issue here, it is a lack of main power to somewhere. The ignition switch supplies power to the dash fuse panel so if power is getting to all the dash fuses with the ignition switch ON then the trouble is after the ignition switch and fuse panel. The ignition relay supplies power to a number of engine related areas. The relay would be a prime suspect for this trouble except for the fact you say that the dash warning lights and headlights don't work when the problem happens. Those things are not related to the relay. Connector F44/B61-pin 3 has a red wire that supplies power from the ignition switch back to the Main fuse panel in the engine compartment which gives power to the headlight relay coils but not the warning lights in the dash. Lets first verify all the fuses in the dash panel are getting power to them while the trouble is happening.

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@Fairtax4me - radio does not turn on in ACC or ON positions.

 

@Cougar - confirmed NO 12V at pin3 either side of F44 or B61 in any key position.

I checked voltage from the neg of the battery to the fusible link terminal with IG on - there is 12V there and the link is still good (0V side to side).

 

12V is getting to pin 12 B52 (interior fuse panel for airbag) when I turn key to ON.  This pin is switched from the key and not powered through the ignition relay.

 

Anything downstream of the ignition relay is still not working.

 

It is all hell trying to get hands on that ignition relay.   :angry:  I can't get it out.  So I have to try testing it in place.

 

But I did manage to but a probe on the light green wire on the relay and read 35mV with the Key-On.  This is the coil for the ignition relay.  The other side - lo and behold - is driven by the ECU.  

This means the ECU does actually have control of the ignition relay.

 

Need to change approach - wasn't really expecting ECU to be upstream of the ignition relay - though it now makes some sense.

 

Going to take apart passenger floor board to get some readings directly from the ECU now.

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Measured voltage at light green pin on ECU connector when connected to unit and Key On.   No significant voltage.  Which means the ECU isn't commanding the ignition relay.

 

Something in the dash is clicking softly (not light A/T interlock or fuel pump relay which is pretty loud).   

 

When I manually actuate the override for the gear select, the solenoid in the column clicks and I can move the shift selector.   

 

But when I press the brake pedal and try to change the gear selector (no override) then it doesn't pull on the shifter solenoid.

At this point, I am hovering over the notion that the ECU is not happy.  Maybe because the A/T inhibit switch is not working correctly?  Still testing - and tearing more things apart.  :(

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Do you get 12v on both sides of the link?

Measuring across it doesn't tell you much. Keep your meter grounded to the battery negative and check voltage on each side of the link.

 

Also remove the SBF fuses in the underhood panel and check them. They may not appear blown but can still be broken. SBF2 supplies power to the main relay, ECU, and fuel pump relay.

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Measuring across simply says the link is good when plugged in -  no potential.  In any case the link was still good when removed and ohmed out (close to 0 ohm).

And yes, there is 12 V on both sides of the link terminals with the meter grounded.

Both SBF2 and SBF1 have been removed and verified close to 0 ohms (good) - and beaten around a little to make sure.  All the SBFs in the engine bay box have been tested similarly along with the fuses throughout both panels.

 

I'm stuck mentally - Now the drinking starts..... :drunk: .  Might look at going to the junkyard this week to pick up an ECU.  That's about all I can do on this today. :( .

 

:excl: I did squeeze in one more test - I am getting 12V at the ECU with Key-On on the red wire at pin #39 of B84 (the big blue ECU connector).  This means I am definitely getting power to the ECU.  But it is unhappy.

Edited by JPX

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No voltage on pin 3 of connector B61 is a problem. The red wire should tie to the ignition switch on connector B72 pin 5. You need to find the break in the wire connection if power is getting to pin 5 at the switch. I wouldn't do anything else until you have fixed that issue. That wire also ties to fuse 18 in the dash fuse panel. An easy place to check for power also.

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No voltage on pin 3 of connector B61 is a problem. The red wire should tie to the ignition switch on connector B72 pin 5. You need to find the break in the wire connection if power is getting to pin 5 at the switch. I wouldn't do anything else until you have fixed that issue. That wire also ties to fuse 18 in the dash fuse panel. An easy place to check for power also.

 Confirmed to have power at pin 3 B61 / pin 5 B72 / pin 3 F44.  Can also see the voltage on fuse 18.

 

An additional detail, with the key ignition on, the headlights will turn on with the switch.  But the parking lights do not. Fuses 16, 17, 18 verified again they are good.

Sounds like the ABS pump is working (fuse 18) - it chirps very quietly twice  at key ignition on.  It stopped when I took out fuse 18.

 

Going to take a closer look at FB-4 (fuse 16) at F45/B62 pin 1 (yellow).  

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Your meter can lie to you.  Check out Load Pro on you tube.

 

I had a 97 Impreza would randomly quit.  Turned out to be the main relay.  I'd take the time to take it out, and yes its tucked up in there.

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If it seems like you're getting power in all the right places then you need to check the grounds for the dash. I think there's a set bolted to the dash near the steering column. There are also grounds on each side of the center dash console at the base of the dash near the floor. Ground wires are brown, and hey do tend to ground several wires all in the same place so there should be 4-5 wires coming together at each ground point. 

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Thanks for the tips guys.  I went through a lot of grounds in the engine bay and under the dash, including the set on the TCM and the steering column - removed, wire brushed and retightened.  Still no change.

 

I was thinking a bit more about the LG wire from the ECU pin#63 that goes to the coil of the main relay pin#2 B48. Since I have power there, that means the coil is getting power.  So either the ground for the relay is bad, or the coil and/or contacts for the main relay are bad.   Will have to try to get under the dash tomorrow to figure that out.

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Hmmm, after spending an hour in various contorted positions, I got the main relay out to bench test.

 

For future reference, the relay is mounted to a small metal plate that is held to the left dash wall with a a phillips screw.  Unless you tore out half the wiring harness or pulled the dash, it would be a miracle to be able to remove the relay from the metal plate with that screw in.  

 

On the bench:

- Main relay tested 77 ohms across the coil (pins 1 and 2),

- Main relay clicked with 12V across coil

- continuity on pins 3 to 5,  and pins 4 and 6 with coil energized

 

Fuel pump relay 

- 70 ohms across coil pins 1 and 3

- continuity on pins 2 and 4 with coil energized

 

Would be really nice to know what the ECU logic tree is when power is applied to it.  

Wondering if I am look at the wrong spot.....if the ECU is bad, it is totally bad.   No good way to troubleshoot the ECU itself at the pin level. 

 

The other side of this is if the inhibitor switch on the gear selector is doing something funny to make the ECU or the TCM not turn on.

 

Going to reconnect everything, but leave the lower dash disassembled and take some more readings:

- verify LG wire is good from the main relay pin 2 B47 back to the ECU pin pin 63 B84.

- check ground/continuity from main relay pin 1 B47   Might hard wire that pin to ground just to be sure.

- recheck all ECU related grounds (mounting bolts/brackets).

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Are you getting 12V to the DLC with key off? If you plug a code reader into the DLC does it turn on? That should be powered all the time. 

The same power that is supplied to the DLC also goes to the ECU, and is the constant power for the ECU IIRC. 

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Are you getting 12V to the DLC with key off? If you plug a code reader into the DLC does it turn on? That should be powered all the time. 

The same power that is supplied to the DLC also goes to the ECU, and is the constant power for the ECU IIRC. 

Interesting.  No voltage at the DLC (I presume you mean pin 5 B78) with the key on.  

Currently rechecking fuse 15 and its terminals - which checked out okay.

 

I don't have  DTC reader - only the OBD reader.

 

I am getting 12V solid on pin 39 B84 at the ECU.  Power of some type is getting to the ECU.  The voltage does drop slightly to 11.2V when cranking the engine.  

Edited by JPX

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Also I found out what the "2 barks" sound under the hood was.....it is the ABS pump initializing at key on.  So at I know that still works.

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Sorry, industry term for the OBD connector is DLC.

Pin 1 in the OBD connector. B40. Red wire. Should show 12v all the time.

Same wire feeds the Main relay, and fuel pump relay, and supplies power to the ECU on pin 39.

 

Forgot that Subaru calls the yellow SSM connector the DLC.

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Pin 85 on B84 is ignition power. Yellow wire.

Same wire supplies 12v to the yellow wire on the ignition coil.

Should be 12v with key on.

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Using the slits on top of the fuses for your meter probe please verify that fuses 1,8,15, and 16 are getting power to them when the ignition is ON. Check both sides of each fuse. There should be 12 volts on both sides if the fuse is good. If the blower works fuse 15 should be okay. If it doesn't work that will be a big clue to work on. Fuse 15 powers a lot of critical things, including the warning lights.

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I took the entire interior fuse block out of the car and took it apart.   It is made up of three layers of metal traces sandwiched between the plastic plates.  I found a small spot of corrosion in the lowermost section of the box (at the i5 connector).  I've seen something like this on Volkswagens where the windshield leaks directly into the fuse block.  I cleaned it up and tested continuity across multiple traces. I went through all the fuses themselves for continuity then reassembled and put back into car.

 

But I never noticed those metal tabs on the backside of the fuses Cougar!  I'll test these out this morning.

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Corrosion problems inside the fuse panel has happened to a number of folks, particularly with the panel under the hood. 

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Pin 85 on B84 is ignition power. Yellow wire.

Same wire supplies 12v to the yellow wire on the ignition coil.

Should be 12v with key on.

 

OBD connector red wire pin 1 B40 is 12V.

Pin 85 on B84 is 325mV to ground with key on.

 

 

Using the slits on top of the fuses for your meter probe please verify that fuses 1,8,15, and 16 are getting power to them when the ignition is ON. Check both sides of each fuse. There should be 12 volts on both sides if the fuse is good. If the blower works fuse 15 should be okay. If it doesn't work that will be a big clue to work on. Fuse 15 powers a lot of critical things, including the warning lights.

 

I probed fuses 1,8,15,16 - red test lead to fuse tips and black lead to dash metal.  325mV on all of them.  I do get 12V on the wiper fuse #2.

 

Guess I need to go after taking apart the engine fuse block next. 

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Power to those fuses comes from the ignition switch via a red wire. Check the wire connection between the switch output and the fuse panel. You're hot on solving the issue now.

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All kinds of 12V from the back side of the fuses on the engine fuseblock.  

 

Just to be sure, I took apart the fuse block down to the mutilayer traces.   No moisture or corrosion (despite the close proximity to the battery).  There was a lot of dielectric grease smeared around in there.  Wiped it down just to eliminate that as a variable.

 

Hmm.....something somewhere between the main engine fuse block and the interior fuse block. :unsure:

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Ah!  A big change!

 

When poking at pin 10 B52 at the interior fuse block to check voltage, all the warning lights came on.  With some wiggling at this connector, I could get the car started!  Even though I had voltage at the ignition switch connector B72, something funny was going on at the fuse block on B52.

 

It choked here and there as I tugged on various portions of wiring under the dash.  But I could get a running car if the connector was happy.

 

As I look at the connector, there is some blue discoloration, similar to the stuff I saw inside the fuse box - probably same location.   I will have to clean up that pin.....and if I can't get a satisfactory connection, may rewire it altogether.

 

Was able to drive the car off the street and into the garage so I can clean up under the dash. 

 

Cougar, Fairtax4me - thanks for the advice!  Hoepfully others can learn from this experience as their Subarus age.

 

Cheers! :drunk:

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