2005 GMC Envoy Error Code P0128 - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum



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  #1  
Old 08-04-2010, 04:05 PM
PeterC PeterC is offline
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2005 GMC Envoy SLT
Silver Mist Metallic 4.2L I6 4X4
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Location: Rexford,NY
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2005 GMC Envoy Error Code P0128

Got a check engine light the other day. Went to Advance Auto Parts to use their OBD2 Scanner. Got code P0128, which I believe most likely would be thermostat related. Engine temp is still 210. I have about 61,00 miles on it. Any advice. I think the thermostat is located off the lower radiator hose behind the alternator driver side???

Thanks in advance.
Pete
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  #2  
Old 08-04-2010, 04:46 PM
christo829's Avatar
christo829 christo829 is offline
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2004 Chevy TrailBlazer LT
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Sounds like you've already looked it up... I thought there was a
sticky around here someplace that discusses the replacement process,
but darned if I can locate it. Try this:

http://forums.trailvoy.com/showthrea...ght=thermostat

The gauge isn't always the most accurate thing in the world. It's just
showing what the PCM thinks you'd like to see most of the time. That
P0128 might be getting thrown due to a partially open stat that doesn't
allow the engine to heat up as quickly as the PCM would like. It may *get*
to 210, but the PCM looks for it to get to a certain temperature within
a certain time. If it doesn't, it tends to throw the P0128 code.

It's possible for the coolant temperature sensor to be flaky, but that usually
causes more erratic behavior in the gauge.

Thermostats are still a general wear item. On my older vehicles, changing
them every year was normal maintenance. These seem to last longer,
but they can still easily fail.

With a 2005, you're close to needing the 5 year coolant change anyway.
I'm overdue with mine, but decided to get therm., coolant, and hoses
and do all of them at the same time...

Good Luck!

Chris
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  #3  
Old 08-04-2010, 06:07 PM
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Topher Topher is offline
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2002 GMC Envoy SLT
Light Pewter Metallic 4.2L I6 4X4
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In case it's needed, here's a full description of what causes a P0128:

DTC P0128

CIRCUIT DESCRIPTION
An engine coolant temperature (ECT) sensor monitors the temperature of the coolant. This input is used by the powertrain control module (PCM) for engine control and as an enabling criteria for some diagnostics.

The air flow coming into the engine is accumulated and used to determine if the vehicle has been driven within the conditions that would allow the engine coolant to heat up normally to the thermostat regulating temperature. If the coolant temperature does not increase normally or does not reach the regulating temperature of the thermostat, diagnostics that use ECT as enabling criteria may not run when expected.

This DTC will only run once per ignition cycle within the enabling condition. If the PCM detects the calibrated amount of air flow and engine run time have been met, and the ECT has not met the minimum thermostat regulating temperature, DTC P0128 sets.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P0128 Engine Coolant Temperature (ECT) Below Thermostat Regulating Temperature

CONDITIONS FOR RUNNING THE DTC

* DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0130, P0131, P0132, P0133, P0134, P0171, P0172, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0335, P0336, P0351-P0356, P0442, P0446, P0452, P0453, P0455, P0480, P0496, P0502 and P0503 for automatic transmission only, P0601, P0602, P0604, P0606, P0621, P1133 are not set.
* The ECT is less than 75C (167F) , but less than 70C (158F) .
* The intake air temperature is more than -7C (+19F) .
* The engine is running between 30 seconds and 30 minutes .
* The vehicle has traveled more than 2.4 km (1.5 mi) at more than 40 km/h (25 mph) .
* The mass air flow (MAF) calculated is more than 15 g/s .
* This DTC runs once per ignition cycle when the above conditions are met.

CONDITIONS FOR SETTING THE DTC

* The calibrated amount of engine run time has been met
* The calibrated amount of engine air flow has been met
* The calibrated vehicle speed and distance have been met.
* The calibrated ECT of 80C (176F) has not been met

ACTION TAKEN WHEN THE DTC SETS

* The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
* The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC

* The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
* A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
* A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
* Clear the MIL and the DTC with a scan tool.


And below is a location of the thermostat. Pretty easy. Remove alternator, remove thermostat. Replace thermostat, then replace alternator.

I also did my coolant flush, upper and lower radiator hoses when I did my alternator...plus I needed to do my water pump.

My thermostat lasted 197k miles . Also, note that the thermostat and the thermostat housing are all one piece made together.
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  #4  
Old 08-04-2010, 08:17 PM
PeterC PeterC is offline
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Thank You
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  #5  
Old 08-04-2010, 08:23 PM
PeterC PeterC is offline
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I just did a coolant change last month when I replaced the water pump. I reset the check engine light and it has not come back yet, but it will.

Pete
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  #6  
Old 08-04-2010, 08:40 PM
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Topher Topher is offline
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Quote:
Originally Posted by PeterC View Post
I just did a coolant change last month when I replaced the water pump. I reset the check engine light and it has not come back yet, but it will.

Pete
Oh, that sucks! Well, try to capture what you can in a clean container and reuse it so you don't waste $ on newer new coolant.
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  #7  
Old 05-10-2011, 11:05 AM
Due51 Due51 is offline
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I have thrown code P1028 and want to replace the thermostat myself (the dealer where I get my Lifetime Oil Changes quoted $410.50).

EDIT: I just read the linked thread above about changing the thermostat without removing the alternator.
My question now is, how much coolant should I expect to spill once I remove the hose from the housing?
Also, what is the proper procedure for refilling to the correct level?

Thanks in advance. This site is a tremendous resource and my 189,000 2004 Trailblazer thanks all of you.

Due
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