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Dave Nova
Dave Nova, Saturn Technician
Category: Saturn
Satisfied Customers: 19452
Experience:  ASE Master Certification. GM World Class Certification
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Saturn VUE: t the low coolant temperature check engine light

Customer Question

t the low coolant temperature check engine light (P0128 I think).....took it to Pep Boys who said bad thermostat, and bad ECT. They replaced both, did a coolant exchange with this (idk if it's the right kind for the engine) the low coolant light has come on (different than's red and in the center instead of the left) despite the coolant resevoir being full. This happened right after Pep Boys did the work. Why is this light coming on and what caused it?

----2002 Saturn Vue AWD v6
Submitted: 4 years ago.
Category: Saturn
Expert:  Dave Nova replied 4 years ago.
Hello and thank you for trusting me with your question. My name is XXXXX XXXXX I will do my best to help you with your Saturn problem.

The low coolant light is controlled by a sensor in the coolant reservoir. First make sure the level is correct, then try unplugging the sensor connector (shown in red in the picture below) and see if the light goes out. If it does, there is a problem in the coolant level sensor. Sometimes you can free up the sensor by tapping on the top of the reservoir with a rubber mallet. If this does not work then the reservoir has to be replaced, the sensor is made into the reservoir.

Customer: replied 4 years ago.

Does and should Pep Boys cover this (parts & labor), based on what I already paid them for (thermostat replacement, ECT replacement, coolant exchange)?

It came with a parts and labor warranty, but I don't know enough about this stuff to know if it qualifies.

Expert:  Dave Nova replied 4 years ago.

The sensor can sometimes stick when the coolant is drained out of the system. I would take the vehicle back and tell them that the light has come on as a result of the work they did. They may be able to unstick the sensor for you.

Dave Nova and other Saturn Specialists are ready to help you
Customer: replied 4 years ago.

They denied their service as the cause of the low coolant light.


They said that the fuse/sensor was already about to die and when they replaced the thermostat/ECT/coolant exchange, the fuse/sensor died on it's own.


Also, the check engine light came back on for the same code (P0128 - low coolant/thermostat/ECT), and they said they fixed it, but the code was related to the sensor with the low coolant light.


I believe I was scammed by your typical auto repair shop and filed a formal complaint with the corporate customer relations @ 1-888-PEP-BOYS.


Can you verify or contribute to any of these statements that Pep Boys said? I believe they purposefully spend 30+ minutes saying car jargon to eventually get the customer confused and to just leave

Customer: replied 4 years ago.
Can you help with this?
Expert:  Dave Nova replied 4 years ago.

I am sorry you are having so many problems with the repair shop. It would seem that a national chain with a reputation to protect would be more willing to help.

The coolant level sensor may be hard to prove that the damage occurred while at their shop. You know that the low coolant level light was not on previous to the repairs and was on afterwards. They should have made notes as to any lights that were on prior to and after the repairs as well. Since this cannot be proved, replacment of the reservoir is likely going to be your expense.

The code P0128 only sets when the coolant temperature does not come up to normal levels. This is only controlled by the thermostat, nothing else. The low coolant level sensor has no bearing on this issue. They diagnosed this problem correctly as a thermostat, but obviously the thermostat is faulty. They should cover this repair again under their guarantee or refund your money. GM developed a new part number for the thermostat to help with issues like this. I am not sure what part Pep Boys used, but if it was not the Genuine GM replacement, you are likely to continue having issues.

Customer: replied 4 years ago.


Did you ever get credit for helping me?

Expert:  Dave Nova replied 4 years ago.

Yes, I did get credit. Thank you very much for asking.