2006 Saturn Ion Code PO128

Tiny
JOE1953
  • MEMBER
  • 2006 SATURN ION
  • 2.2L
  • 4 CYL
  • 4WD
  • AUTOMATIC
  • 143,000 MILES
Engine light come sometime when driving I had the computer scan and the code is PO128 and they said the thermostat is going bad will you explain this code PO128 do I need to replace the thermostat? The engine is not over heating but I don't think I am getting the gas mileages I once was. Will a bad thermostat decrease the gas mileages?
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Sunday, May 25th, 2014 AT 3:17 PM

11 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
Basically, the engine isn't getting warm enough quickly enough. There are three things that could cause this code. They are low engine coolant level, stuck open thermostat not allowing the engine to warm up, or a faulty cooling fan that is running too much and cooling the engine. All the time.

Chances are the t-stat is staying open all the time or opening too quickly, but check the other two things too.
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Sunday, May 25th, 2014 AT 4:23 PM
Tiny
SATURNTECH9
  • EXPERT
I have seen that code alot on those 2.2L ecotec engines if the coolant level was low the coolant temp sensor would still read hot. What happens is the thermostat has a rubber seal where the coolant flow is sealed off. That seal goes bad over time and allows coolant to flow thru it before it opens so the computer doesnt see the engine warm up quick enough. So it sets that code the number one fix is the thermostat. Just had two ions a 2005's with that code replaced the thermostat on both.
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Sunday, May 25th, 2014 AT 4:53 PM
Tiny
JOE1953
  • MEMBER
Where is the thermostat located is it easy to replace or get to?
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Sunday, May 25th, 2014 AT 6:48 PM
Tiny
SATURNTECH9
  • EXPERT
Depending on your skill level how hard it will be for you its pretty easy for me. On the back side of the engine at the end of the large steel tube on the drivers side.
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Monday, May 26th, 2014 AT 5:18 PM
Tiny
JOE1953
  • MEMBER
I couldn't located the large steel tube on the back side of the engine what it is connected to is the thermostat inside a housing how many bolts in it can you send me a photo of the large steel tube?
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Saturday, June 21st, 2014 AT 8:35 PM
Tiny
JOE1953
  • MEMBER
The engine coolant level is full. I run the air conditioning all the time will that causing the cooling fan run to much and cooling the engine all the time? The computer do have a code PO128.
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Thursday, July 10th, 2014 AT 6:15 PM
Tiny
SATURNTECH9
  • EXPERT
The cooling fan will run as long as your ac is on thats normal and wont hurt anything but that wont set a p0128.
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Friday, July 11th, 2014 AT 5:55 AM
Tiny
JOE1953
  • MEMBER
I had a engine code PO128 and the engine light was coming on sometime so I replace spark plugs and the rubber boots the engine light havn't came on anymore while driving what does code PO128 have to do with engine light coming on replaceing spark plugs?
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Wednesday, July 16th, 2014 AT 12:06 PM
Tiny
SATURNTECH9
  • EXPERT
Nothing I have seen the p0128 code set in the computer and not turn the light on. It needs a new thermostat I have replaced a lot of them for that code.
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Wednesday, July 16th, 2014 AT 12:28 PM
Tiny
JOE1953
  • MEMBER
After I replace the spark plugs the engine light don't come on any more when driving and I don't have that code po128 now by me replacing the spark plugs and rubber boots did that stop the engine light from coming on when driving? The enging light don't come on when driving now.
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Wednesday, July 16th, 2014 AT 4:16 PM
Tiny
SATURNTECH9
  • EXPERT
The spark plugs cant and wont set a code for the thermostat not working correctly its impossible they dont have anything to do with the cooling system. Thats about all I can tell you.
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Wednesday, July 16th, 2014 AT 7:07 PM

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