2001 Legacy cutting out at speed

[dmopincarne]

Hi,

 

I'm new to the board and have a problem I hope some of the experienced Subaru people here can help me track down.

 

Last night, while on the highway, my 2001 Legacy wagon suddenly 'grabbed' like someone had slammed on the brake. I had caught a glimpse of the ABS light just prior to the 'grab' and because I had just added air to a tire that was low, I initially thought it might be a problem with the traction control or ABS. Alert now (and with a death grip on the wheel) it happened again a few minutes later and I now noticed that the AT Temp light was also coming on just prior. As I got of the highway and nursed it home, the problem continued, even at surface street speed although the grabbing effect was not as pronounced.

 

So here's some specific observations:

 

• 
  The first indication that something is about to happen are the ABS and AT Temp light come on
  The speedometer needle also takes a nose dive
  There is NO Check Engine light coming on
  When these symptoms disappear, the car instantly begins to run normally
  The engine does not otherwise run rough and is asymptomatic
  The car does not loose all power; the instruments remain lit and the warning lights remain on.
  

 

It's as if the key were being turned from run to accessory position. Because of the behavior of the instruments, I'm assuming that either the ignition or sub-circuit have a fault in them somewhere. Since the car doesn't 'go dark' I'm assuming that continuity with the battery is in tact but I don't know about voltage. Also, the grabbing that I'm experiencing on the highway could be the compression of the engine as the ignition cuts out. I'm assuming that at highway speed there will be enough speed for the torque converter to remain engaged and either it or the flex plate are restarting the engine once the circuit restores itself.

 

I've talked to a local Subaru specialist and he indicated the problem is most likely in the battery, the alternator, or the voltage regulator. The alternator is about two years old. I don't know Subarus very well but I'm assuming the regulator is internal to the alternator.

 

I've checked the stickies and search results have listed a few threads with similar symptoms, but most of the suggested solutions deal with faulty engine sensors while my problem seems to be connected to a faulty circuit.

 

If anyone knows of problem areas in Subarus such as wiring harnesses, fusible links, relays, circuit breakers, etc. that might relate to these symptoms I'd appreciate hearing from you.

 

Much thanks for any leads

[Fairtax4me]

And NO CEL? Can you confirm that the CEL works during the bulb test when starting the engine?

Guessing this is an auto trans since you have the AT temp light?

Which engine are we dealing with? And how many miles on it? Any recent service work?

[wtdash]

A couple of things to check: What's the AT's fluid level? Yours also has an AT spin-on filter, I believe. If it were clogged, it may cause your symptoms?

 

GL,

TD

[OB99W]

I'm new to the board and have a problem I hope some of the experienced Subaru people here can help me track down.

Welcome to the forum.

 

The ABS warning light is controlled by the ABS ECU. The AT Oil Temp warning light is controlled by the TCU. Both of those control units can misbehave if the voltage supply drops sufficiently. Your Subaru specialist might be on the right track.

 

Loss of alternator field current on Subarus typically causes the battery and brake warning lights to illuminate, but their not coming on doesn't guarantee that there isn't a battery or charging system problem.

 

One thing you could try, to see if you can 'provoke' the problem, is to heavily load the electrical system. That can be done by simultaneously turning on several things that draw substantial current -- headlight high beams, rear defogger, heated seats (if you have them), etc.

 

By the way, was it unusually cold last night in WA? (I've heard that the weather there has been a bit strange lately.) Marginal electrical connections can become worse due to contraction of metal contacts with cold.

[dmopincarne]

Thanks for the responses so far. I'm ruling out problems with the ABS and AT since I doubt they would cut out simultaneously and take the spedo with them. Given that the engine otherwise runs fine and this is an instant on, instant off event, I'm reasonably certain that either a faulty connection or component is at the heart of it. The problem is that, given the intermittent nature of the problem, knowing where to look.

 

The more I think about it, it really is like the key was momentarily turned one step back (Ignition turned off) I know that when they are first energized, ABS systems typically do a self test. Assuming that the circuit is being temporarily interrupted, could the grabbing be accounted for by the ABS system re-initiating?

 

Also, is it likely that the voltage could drop enough to cause the ignition to cut out but remain high enough to keep the accessories going?

 

I haven't put any test equipment on it, but if the battery is charged and the regulator/field cuts out, would this account for the symptoms? Wouldn't the battery still power the ignition circuit or would this cause a loss of continuity?

 

Finally, wouldn't a faulty alternator/regulator/battery cause a charge/CEL to illuminate?

 

Thanks again

 

Dave

[nipper]

The CEL ONLY is related to emissions, it could really care less about anything else.

 

Subarus will backfeed power in wierd ways when the ALt starts to fail or has failed. The Brake light on the dash is one way, so is the abs. The atf is new to me but hey like i said it is weird.

 

I doubt it is the battery as that is used for starting and to assist at low alt output and high load. At speed (over 1800 rpm) the alt is putting out enough power to run everything and charge the battery. Once the battery is happy it just runs the car.

 

Your car is old enough to need a battery but do not replace it yet.

 

I dont normally recomend things like this (IE gimmick) but they used to make a voltage indicator that plugged into the ciggy lighter/power recepticle. I want you to find one of these (JC Whitney maybe). When the car coughs, look at the voltage reading. Since this is so far an intemittant issues, it will be hard to chase down. It can be a bad voltage regulator, but I cant see that bing a once then fine thing, I would see it more as a happening when hot, fine when cold thing. May be as simple as a belt going bad.

 

Start with the cheap one, a belt. hrmmmm if this has a belt tensioner on it (blame the vicodin for my not knowing right now) check that too. It may be starting to fail.

[dmopincarne]

Problem solved! The battery tie down strap had come loose and was intermittently sliding aagainst the positive post and grounding it out.

[nipper]

Problem solved! The battery tie down strap had come loose and was intermittently sliding aagainst the positive post and grounding it out.

 

 

Your lucky. Otherwise it coulfd have been

 

"Subaru burning over an open fire, Tow trucks waiting at the shell"