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how do i replace a thermostat on a 2003 GMC envoy


what size engin?

what size engin?

I do believe it is a 4.2

I do believe it is a 4.2

Throwing parts at a problem

Throwing parts at a problem till the problem is repaired is a waste of time and money. A part should (NEVER)be changed untill it is checked and (CONFIRMED) to be defective.

TELL US IN DETAIL HOW YOU CHECKED THE THERMOSTAT?
TELL US IN DETAIL EXACTLY WHAT THE PROBLEM IS?

TELL US IN DETAIL HOW YOU DETERMINED THE THERMOSTAT IS THE SOURCE OF THE PROBLEM?

I do believe it is a 4.2

I do believe it is a 4.2

THE ENGINE SIZE DOESN'T

THE ENGINE SIZE DOESN'T MATTER !!!!

Answering the questions that continue to go un-answered does. Understand that this is (ONLINE) auto repair and we don't have your Envoy in front of us to run any tests on. If we (DON'T) ask questions and if you (DON'T) answer them, then we can't help you

The check engine soon light

The check engine soon light came on. The heat is fine, there is no over heating. We took it to auto zone to have them check it and the little machine said it was the thermostat. and listed no other problems.

The guy at auto zone said

The guy at auto zone said that the flap must be stuck open also.

Thanks for posting something

Thanks for posting something that we can finally use to help you with.

What was the actual code (NUMBER) that Auto ZONE read for you?

Was it a "CTS" (Coolant Temperature Sensor) error?

My husband said it was

My husband said it was something about the thermo sensor

if the code is for the engin

if the code is for the engin staying cold for too long, there could be a few reasons for that.
here's abulletin for one cause, read it and let us know if you think it could be the cause.

Electrical - SES Lamp ON/DTC's P0480/P0526/P1481/P1484

Bulletin No.: 05-06-02-012B

Date: October 19, 2006

TECHNICAL

Subject:
Service Engine Soon (SES) or Check Engine Light On, DTC P0480/P0526/P1481/P1484 Set (Replace Engine Cooling Fan Wiring Harness)

Models:
2004-2006 Buick Rainier
2002-2006 Chevrolet TrailBlazer, TrailBlazer EXT
2002-2006 GMC Envoy, Envoy XL
2004-2005 GMC Envoy XUV
2005-2006 GMC Envoy Denali, Envoy XL Denali
2002-2004 Oldsmobile Bravada
2005-2006 Saab 9-7X

Supercede:

This bulletin is being revised to add DTC P1484. Please discard Corporate Bulletin Number 05-06-02-012A (Section 06 - Engine/Propulsion System).

Condition

Some customers may comment that the Service Engine Soon (SES) or Check Engine light is illuminated. This condition may be intermittent and upon investigation, the technician may find either DTC P0480, P0526, P1481 or P1484 set.

Cause

This condition may be caused by the cooling fan harness chaffing against the plastic guide it routes through. This contact may damage the insulation of the wires enclosed in that harness.

Correction

Replace the engine cooling fan harness using the procedure listed below.

Remove the cooling fan. Refer to the Cooling Fan and Shroud Replacement procedure in the Engine Cooling sub-section of SI.

Place the cooling fan assembly on a bench.

Disconnect the harness electrical connector from the cooling fan clutch.

Remove the harness from the plastic guide while feeding the wires out of the slot.

Before installing the new harness, wrap the affected area on the wires with electrical tape to keep the protective sleeve in place. Be sure to keep the tape approximately 25 mm (1 in) away from the connector so the wires can be fed into the slot.

Feed the wires into the slot and install the harness to the plastic guide.

Connect the harness electrical connector to the cooling fan clutch.

Install the cooling fan. Refer to the Cooling Fan and Shroud Replacement procedure in the Engine Cooling sub-section of SI.

Is the coolant level full? Do

Is the coolant level full?

Do you find yourself adding coolant frequently?

Has the (COOLING SYSTEM) been (PRESSURE TESTED) to (RULE OUT) leaks?

Make sure the wire connector at the "CTS" is on tight and free of all dirt and corrosion.

In order for us to provide you with the (MOST ACCURATE) repair information, we (NEED) the (actual) error code that Auto Zone read for you.

If necessary go (BACK) to any Auto Zone store and have ANOTHER)scan done. This time (WRITE) the code down so you don't forget it, then post it so we can see it.

Coolant level is full. No

Coolant level is full.

No don't have to add coolant at all.

Thank you I will get the code as soon as possible.

Coolant level is full. No

Coolant level is full.

No don't have to add coolant at all.

Thank you I will get the code as soon as possible.

To expedite the repair, and

To expedite the repair, and until you (POST BACK) with the (CODE), the items we mentioned (SO FAR) should be either:

RULED IN or RULED OUT !!!!

the code is; t0128 coolant

the code is;

t0128 coolant temp below thermostat regulating temp

t0014 cam position, actuator b-bnk1 timing over-advanced.

how does it run?

how does it run?

mrsshaffer25, After start-up

mrsshaffer25,

After start-up the engine in your Envoy must reach normal operating temperature within a specific amount of time. The setting of PO128 means that the “PCM” (aka vehicle computer) has detected, that the specific time has lapsed and the engine still hasn’t reached normal operating temperature. Simply stated, it’s taking longer than the normal acceptable time period for your Envoy’s engine to warm up.

RULE OUT:

Engine coolant issues (air pockets in cooling system)

Low coolant level

Coolant leaks (via a cooling system pressure tester)

Stuck open or leaking thermostat

Wrong thermostat for particular engine

Defective cooling fan (Fan runs too much or too long)

Defective coolant temperature sensor

Issues with “CTS” wiring (and or) circuits

Issues with “CTS” wire connector

Issues with “Intake Air Temperature” sensor

Posting “Freeze Frame” and “Live Data” would help.

For now ignore POO14. There’s a technical reason as to why I’m telling you to ignore it, but I don’t want to bore you with a 200 page answer. Simply stated, PO128 is causing POO14 to set. Resolve PO128 and you’ll resolve POO14.

Best Regards
Sam


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