Codes P0171, P0174

Tiny
SERGIOB
  • MEMBER
  • 2000 MERCURY SABLE
  • 3.0L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 129,900 MILES
The engine light is on, climate control blows hot air only, are these two problems related? The climate control uses engine vacuum, right?
Tuesday, April 26th, 2016 AT 3:58 PM

1 Reply

Tiny
CARADIODOC
  • MECHANIC
  • 33,873 POSTS
P0171 - System too Lean (Bank 1)
P0174 - System too Lean (Bank 2)

On HVAC systems that use vacuum-operated motors, those are usually only for the mode doors. Temperature doors typically aren't vacuum-controlled. If the vacuum hose feeding the heater controls is broken, that could cause enough of a vacuum leak to cause the lean conditions, especially when both sides of the engine are affected. The clue would be you'll most likely only get air from the defroster vents and it won't switch to other functions.
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Tuesday, April 26th, 2016 AT 4:15 PM

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