Question about 2002 GMC Envoy

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The running temp of the engine has little affect on the A/C. The condenser for the AC is in front of the engines' radiator, so in that respect there can be a negligible amount of heat transfer between the two. I only mention that as an FYI. Now, more to the point...the engine cooling system and the AC operate independently. The engine drives the AC compressor pump via a pulley. The pulley free-wheels until the AC is turned on and then an electromagnetic clutch engages the pump. That's why you feel (and hear) it engage when you switch on the AC. The pump actually draws a significant amount of horsepower from the engine...say maybe 10-20 horsepower. So your engine does work a little harder and will run a few degrees warmer (but not a lot). And that's why you don't get quite as good of mileage when using the AC. To me, it's worth it.
Now, if your AC is low on refrigerant (the 134A fluid that runs through the tubes under pressure-making it cool when it expands through an orifice as it enters a coil in the cabin area) it won't work so well. You also risk burning up your AC compressor if it's too low. If that happens, you'll know it because the pump will seize up and probably break the serpentine belt that drives it...causing a momentary sensation that the brakes are on. Remember it's driven by the engine via a belt. Once the belt breaks the alternator and water pump also quit because they depend on the same belt. You would certainly have warning lights on your instruments too. This is no time to drive it home or even another block for that matter. It's time to stop and turn it off, have it fixed without another minute of run time. If not? Well, read on.
If your engine is running hot, it's due to something else besides the AC. There are several possibilities but the AC isn't one of them. Overheating is the single most common cause of engine failure. Probably around 90% of engine failure is due to some form of overheating...compared to say, loss of oil. The bad part about overheating is that it sometimes sneaks up on you and it's often too late before you realize it. Believe your senses and the warning lights/gauges! If you shut off an engine before it sizzles, chances are you've saved it from serious damage. I'm talking about seconds, not minutes. And no, the light won't eventually go off if you ignore it, but you will be walking. If it's just running on the high side, have it checked out. A couple hundred bucks today may save you $2000+ next week. Again, it's worth it.
So, bottom line is this. If your AC is low on refrigerant it won't cool the inside of the car to well and that has little or nothing to do with your engine running hot. And NEVER ignore overheating!
Hope this helps. Jim-28 years A&P Aircraft Technician and lifelong performance automotive enthusiast. Good luck.

Posted on Oct 03, 2008

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No not refregerant but yes to antifreeze

Posted on Sep 13, 2008


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SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

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P0128 (and P0116) on 2006 GMC Sierra v-8, 5.3L, 4x4. Originally getting low temp readings on guage. After replacing the thermostat, the problem seemed to be fixed. A few days later, I was getting my...

P0116 - Engine Coolant Temperature (ECT) Circuit Range/Performance Problem
The ECT (Engine coolant temperature) sensor is a thermistor which changes resistance based on temperature of the coolant in contact with it. The ECT sensor will be located in the block or coolant passage. Usually it is a two wire sensor. One wire is a 5 Volt supply from the PCM (Powertrain Control Module) to the ECT. The other is a ground to the ECT.

As the temperature of the coolant changes the resistance on the signal wire changes accordingly. The PCM monitors the reading and determines coolant temperature in order to perform essential engine fuel management. When engine coolant is low, sensor resistance is high. The PCM will see a high signal voltage (low temperature). When coolant is warm, the sensor's resistance is low and the PCM will see a high temperature. The PCM expects to see slow resistance changes on the ECT signal circuit. If it sees a quick change in voltage that isn't consistent with an engine warming up, this P0116 code will set. Or if it sees a lack of change in ECT signal, this code may set.

Symptoms: There may be no noticeable symptoms if the problem is very intermittent, however the following may occur:
MIL (Malfunction Indicator Lamp) illumination
Poor drivability
Black smoke at tailpipe
Poor fuel economy
May not idle
May exhibit stalling or misfires

Causes: Potential causes of the P0116 code include:
Missing or stuck-open thermostat
Bad ECT sensor
Short or open on signal wire
Short or open on ground wire
Poor connections in wiring

Possible Solutions: If there are any other ECT sensor codes, diagnose them first.
Using a scan tool, check the ECT reading. On a cold engine, it should match the IAT reading or should be equal to ambient (outside) temperature reading. If it does match the IAT or ambient temp, check the freeze frame data on your scan tool (if equipped). The saved data should tell you what the ECT reading was when the fault occurred.

a) If the saved info indicates that the engine coolant reading was at the coldest exreme (around -30 deg. F) then that's a good indication the ECT resistance was intermittently high (unless you live in Anchorage!) Check for an open in the ECT sensor ground and signal circuits and repair as necessary. If they appear okay, warm the engine up while monitoring the ECT for any intermittent jumps high or low. If there are replace the ECT.

b) If the saved info indicates that the engine coolant reading was at the warmest exreme (around 250+ deg.F) then that's a good indication the ECT resistance was intermittently low. Check for a short to ground on the signal circuit and repair as necessary. If it appears okay, warm the engine up while monitoring the ECT for any intermittent jumps high or low. If there are replace the ECT.

Other ECT sensor and circuit related DTCs: P0115, P0117, P0118, P0119, P0125, P0128

P0128 Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)
This means that the engine's PCM detected that the engine has not reached the required temperature level within a specified amount of time after starting the engine. The intent of the P0128 code is to indicate a faulty thermostat. Similar codes: P0125

In determining the engine did not reach a "normal" temperature, it takes into account the length of time the vehicle has been running, the intake air temperature (IAT) sensor reading, the engine coolant temperature (ECT) sensor reading, and the speed of the vehicle.

Symptoms: You will likely not notice any drivability problems other than the MIL illumination.

Causes: A code P0128 may mean that one or more of the following has happened:
Low engine coolant level
Leaking or stuck open thermostat
Faulty cooling fan (running too much)
Faulty coolant temperature (ECT) sensor
Faulty intake air temperature (IAT) sensor

Possible Solutions: Past experience indicates that the most likely solution is to replace the thermostat. However here are some suggestions on troubleshooting and repairing a P0128 OBD-II code:
Verify coolant strength & level
Verify proper cooling fan operation (check if it's running more than it should). Replace if necessary.
Verify proper engine coolant temperature (ECT) sensor operation, replace if necessary.
Verify proper intake air temperature (IAT) sensor operation, replace if necessary.
If the above items check out good, replace the thermostat
If Nissan vehicle, check for Technical Service Bulletins (TSBs), as the ECM may need to be reprogrammed to correct the P0128 code

These codes are telling you that the engine temperature is not sufficient. This can be caused by a faulty coolant sensor,air in the cooling system,or a faulty computer.
The engine should run at 190 F & higher when warmed up. Scan the computer system to view engine temperature.

Keep us updated.

Oct 01, 2011 | 2006 GMC Sierra

1 Answer

My problem with FixYa is the idiotic returns on search. For insance, My search is 1997 Ford Thunderbird engine code 141. Fixya returns a reply with a ton of non-related, non-authorative replies. How...

DTC P0141 - O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)
This code means that the heated circuit in the oxygen sensor on bank 1 decreases time needed to enter closed loop. As the O2 heater reaches operating temperature, the oxygen sensor responds by switching according to oxygen content of the exhaust surrounding it. The ECM tracks how long it takes for the oxygen sensor to begin switching. It the ECM determines (based on coolant temp) that too much time elapsed before the oxygen sensor began operating properly, it will set P0141. See also: P0135 (Bank 1, Sensor 1).

You will likely notice poor fuel economy the illumination of the Check Engine Light.

Causes: A code P0141 may mean that one or more of the following has happened:
open or short to ground in the wiring harness
O2 heater circuit wiring high resistance
O2 heater element resistance is high
Internal short or open in the heater element

Note: Typically a failed catalytic converter does not cause this code. You're more likely to see a P0420 code for a failed converter.

Possible Solutions:
Replace oxygen sensor (cannot repair open or short that occurs internally to sensor)
Repair short or open or high resistance in wiring harness or harness connectors

Here is the daignostic procedure for troubleshooting DTC P0141 (click over each image for zoom)...


Hope this helps to solve it.

Sep 27, 2011 | 1997 Ford Thunderbird LX

1 Answer

Temperature guage goes to high, but it doesn't appear that the van is overheating (no steam/fluid leaking) Radiator & thermostat were recently replaced. Guage will jump to high when idle, but...


Aug 21, 2011 | 1996 Ford Econoline

2 Answers

PO103 and 116 code on a 1997 jetta 2.0

P0103 - Mass or volume air flow circuit high input.

Symptoms: Engine stalls, running rough, excessive fuel consumption, excessive smoke from the tail pipe, check engine light on.

Possible Causes: Dirty mass air flow sensor, dirty mass air filter, mass air flow sensor harness is open or shorted, mass air flow sensor electrical circuit poor connection, intake air leaks, faulty mass air flow sensor.

P0116 - Engine coolant temperature circuit range/performance.

Symptoms: Check engine light on.

Possible Causes: Low engine coolant level, ECT sensor harness open or shorted, ECT electrical circuit poor connection, faulty engine coolant temperature sensor (ECT), faulty engine coolant thermostat.

Apr 27, 2011 | Volkswagen Jetta Cars & Trucks

1 Answer

My 97 malabu usually wont start when cold in mornings

Usually a temperature related issue is electronicly related. If you have access to a scanner you may find the coolant temp sensor or another is squed causing it to add too much fuel or not enough for start up. You will also find fuel injectors will change resistance with temperature. If an injector is shorted it will shut down the injector driver in the Engine Control Module. I hope this helps. If you have more questions reguarding this or other conserns please ask me. Please remember high ratings are very important to me.

Thank You,

Aug 28, 2009 | 1997 Chevrolet Malibu

1 Answer

Recharge air on a 1998 oldsmobile bravada

You didnt actually post a question so I will try to help. You need 134a refrigerant and a way to get it into the system. Places like walmart and Advance Auto Parts has what you need. Most diy kits have a hose to connect to the Low Pressure side of the ac system and a guage. The other end of the guage has a connector that fits on the can of 134a. Start the car, turn the ac on high, open the hood. Being careful of moving parts under the hood, connect the hose to the Low Pressure side of the ac and see where the guage is reading. Most are color coded. If it says it needs charged, squeeze the trigger until the can is empty and take another reading. Continue until the guage is in normal range.

Jun 23, 2009 | 1998 Oldsmobile Bravada

2 Answers

Guage temp erratic read

Engine tempature probe on block is bad and grounded inside, or the wire leading to the engine block heat sensor is shorted to ground. 

Dec 14, 2008 | 1999 BMW 318 ti

1 Answer

Temperature Guage

You either have an electrical short to the gauge or your temperature sensor on the motor is "out to lunch". Try to manually get your motor temperature with some other sort of thermometer. With a cold engine take the radiator cap off and make sure it is full. Then place a thermometer in being sure to touch the fluid(may sound dumb but don't drop it in the radiator). Start the engine and allow it to come up to operating temperature. Approximately 190 to 200 degrees. Your thermostat should be open at this point and you should notice a flow to the radiator fluid. If the temp holds then you have one of the aforementioned problems. If you have a Haynes manual it should tell you how to troubleshoot the temperature sensor. I believe that I am leaning towards an electrical short of some sort though. An improper ground perhaps. Check and see if there are any fuses that control this system. Once again, the Haynes manual has wiring diagrams that will show you what wires to chase. And it is a chase. wiring problems are hard to find. If the temperature test pans out You may want to buy an after market temperature gauge and mount it up instead. Pull the plug on the old one and be on the road. You may have already solved this problem and I just wasted about five minutes of my life. If not and you have any questions e-mail me at Have fun and be careful. 200 degree fluid is nothing to take lightly.

Sep 30, 2008 | 1999 Toyota 4Runner

1 Answer


the a/c will run based on the pressure switch adn has nothing to do with the temp of the vehicle and or the engine.

If the freon is low initial stages you will hear the clutch clicking on and off and when it becomes extreemly low will not engage the a/c clutch at all/.

Jul 27, 2008 | 2002 GMC Envoy

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