cruise control question

[Don's 04 Outback]

Hi folks,

 

We have a weird problem. When running down the road if I turn on the head lights the cruise control shuts off.

 

If I start out with the head lights on the cruise control wont set at all.

 

I love my cruise it has saved me a lot of tickets.

 

I am thinking maybe a relay that transfers with the head lights, but I am not sure where to look.

 

Thanks for looking. 

[forester2002s]

Many 'weird' electrical problems are due to bad grounding problems.

I would check all grounds associated with the headlights, and cruise-control.

[Fairtax4me]

Year model and engine?

 

Does it also happen of you turn on only the parking lights?

[Don's 04 Outback]

It is an 04 Outback, 2.5 liter, automatic.

 

I haven't noticed if it quits with just the parking lights but I know when tried to use the head lights the cruise quits.

[Don's 04 Outback]

An update, I found a tail light not working. When I opened it up I found corrosion in the light socket. I think that could have created a path for a bad ground like Subaru Fanatic mentioned. I cleaned out the socket, replaced the lamp and the cruise control works again with the lights on or off.

 

Thanks for the help.

[Fairtax4me]

That's where I was heading. Good find.

Cruise uses the brake lamp switch to disable the system if you press the pedal. A poor ground for a shared brake and parking lamp bulb can cause a backfeed that disables the cruise.

[SunnyGardener]

2007 Outback automatic, 4cylinder engine

The check engine light comes on and the cruise control quits.  Computer reader says code 171, running lean. After it's reset, it does it again when I'm on the road.  The interval had become short, and I'm worried about TO WHAT the sensor is responding. Recently replaced an O2 sensor, but a week later it happened again, just driving around town.  It's hot, but that's no excuse, is it? 

I'd sure like for this to be fixed, and hope you people have some ideas.

[matt167]

Subaru's have a failsafe for the cruise. If CEL is on, cruise will not work

[idosubaru]

Ignore th cruise - that's not a symptom here, just a reaction to the existing P0171 code.

 

*** Which O2 sensor did you replace?

*** Why did you replace the O2 sensor? (for this issue or something else - what was that something else?)

 

Intake leaks - check all hose fittings/clamps for proper fit, seating, and tightness.

 

Exhaust leaks - would probably have to be very far forward, in front of the front O2 sensor.

 

Front Oxygen sensor (on that side, if it has two front sensors).

 

I think yours has a MAP sensor, so this doesn't directly apply but the MAF sensor on older Subaru's (pre-2000 outbacks) could need cleaned or replaced due to P0171 codes. Since the MAP sensor replaces the MAF sensor I presume the possibilty exists for it to be an issue here. But I don't think they fail very often so I'd think this a less likely possibility than others.

 

Equally unlikely would be fuel supply (pump/filter) - but considering those easily and routinely make 200,000+ miles without issues that highly unlikely on a 2007.

Edited September 11, 2016 by grossgary