Fan Clutch behavior? - Page 2 - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum



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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 Vortec 4.2L I-6 Engine and Drivetrain > OEM Issues

OEM Issues Original Equipment Repairs and/or Problems

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  #11  
Old 06-10-2019, 01:39 PM
mddombrowski mddombrowski is offline
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2006 Chevy TrailBlazer LT EXT
Summit White 4.2L I6 4X4
Join Date: Jan 2017
Location: Charlotte, NC
Posts: 188
Yes agree with Grinder.

The #1 input to fuel economy in fuel injected engines is the engine temperature. Whether that is actual temperature, or reported temperature is to be determined. I've attached the temp-resistance table below. You will have to measure engine temperature with a separate thermometer, or remove the ECT to known ambient temperature and then measure resistance across the sensor.

But first I'd replace the t-stat and re-check. It and fresh coolant are probably needed anyway unless this has been done within the last three years.
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  #12  
Old 06-10-2019, 07:46 PM
airtight_python airtight_python is offline
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Quote:
Originally Posted by mddombrowski View Post
Voltage is raw data and is used by the PCM to calculate STFT and LTFT. The B1S2 HO2S should show relatively constant voltage at constant throttle. B1S1 should swing back and forth. But now you're wandering from the original diagnosis and just throwing parts.

Start with a new thermostat and fresh coolant and leave the O2 sensors on your bench. If the engine does not reach proper operating temperature, the emissions control system defaults to open loop mode. It will increase the pulse width of the injectors. Fuel trim and the HO2S sensors do not come online until the vehicle switches to closed loop.

Nah, not throwing parts at it. I was just curious how the sensors should read. Thank y'all for the explanations and chart. The O2s appear to be functioning ok. But I'm still replacing them, and the plugs. Haha.

It's nearing 100k and pretty certain they've never been done. Had these parts on list for maintenance after acquiring the truck. Not in lieu of P0526 or P0128.

Coolant temp on warm engine in car scanner reads ~197F while dash gauge is at 210. I'm aware they don't mesh. Just an observation. I'll check the coolant temp sensor for giggles and replace if necessary. There should still be a lot of miles left in this truck with good care.

I'll do the stat and fresh coolant first. Though coolant has probably been changed as I know a water pump was put on in the last couple years. Probably due to the broken fan I replaced when I did the clutch.

But about that fan clutch... another on the way.
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  #13  
Old 06-12-2019, 08:01 PM
tak1313 tak1313 is offline
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In MANY situations where P0128 is thrown, the ultimate problem has been the thermostat failing to regulate coolant flow correctly - ie. stuck open or opening too early. You can easily check the operation by pulling the thermostat and heating it in a pan of water, monitoring the temperature, and seeing at what point it opens - or if, in your case, it even closes when cold.
Since you already have one in hand, i wouldn't even bother testing it and just swap it, since you have to pull the old one to test anyway. It's an easy swap.
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  #14  
Old 06-12-2019, 09:25 PM
airtight_python airtight_python is offline
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Originally Posted by tak1313 View Post
In MANY situations where P0128 is thrown, the ultimate problem has been the thermostat failing to regulate coolant flow correctly - ie. stuck open or opening too early. You can easily check the operation by pulling the thermostat and heating it in a pan of water, monitoring the temperature, and seeing at what point it opens - or if, in your case, it even closes when cold.
Since you already have one in hand, i wouldn't even bother testing it and just swap it, since you have to pull the old one to test anyway. It's an easy swap.
Thanks. Looks to me like the stat might be a pain. Is it not necessary to remove the alternator? And it looks like the alternator would be easier to remove with the fan out. Since the coolant temp sensor may require alternator removal as well, I went ahead and ordered one up and will swap both. Cheap enough.

The fan clutch seller shipped out a replacement pretty quickly. Wasn't expecting it today. Home from work at 5 and just replaced it. The new clutch is much BETTER. But still doesn't seem QUITE right. The P0128 disappeared almost immediately. Need to run it from a cold engine again to be sure.
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  #15  
Old 06-13-2019, 06:16 AM
pctyson pctyson is offline
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2003 Chevy TrailBlazer LS EXT
Majestic Red Metallic 4.2L I6 2WD
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pctyson

Sorry for the double post. I ddeleted the text
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  #16  
Old 06-13-2019, 06:17 AM
pctyson pctyson is offline
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2003 Chevy TrailBlazer LS EXT
Majestic Red Metallic 4.2L I6 2WD
Join Date: Mar 2009
Location: Smithfield, VA
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Fan Clutch

I replaced the fan clutch and thought that would do the trick. I later found that a mouse had eaten some wires to the fan clutch under the engine compartment fuse box. You really need to make sure that the signal is getting from the computer to the fan clutch. If the signal is not there, the fan clutch will remain engaged constantly. Some of the aftermarket fan clutch replacements do need reprogramming or they will come on full speed at first and then eventually settle down.
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  #17  
Old 06-15-2019, 09:41 AM
tak1313 tak1313 is offline
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When I did my stat, I did remove the alternator because it's easy to do - just three bolts (after removing belt) and it's off. I believe some do it without removing the alternator by going through the wheel well and reaching under, but IIRC it does make accessing at least one of the bolts a little awkward. Either way you do it, it's an easy job, even though some make it sound like a PITA.

The temp sensor is a much bigger PITA if you do it because of the location (under the exhaust manifold), but mine is a 2007. I believe the earlier ones are more accessible near the stat.
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  #18  
Old Yesterday, 11:35 PM
judas judas is offline
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2007 Chevy TrailBlazer LT
Graystone Metallic 4.2L I6 2WD
Join Date: Jul 2015
Location: Palm Bay, FL
Posts: 1
'07 TB, I had a fan speed sensor error, let it go for many months cause I was having no issues, the fan engaged when hot and stopped in traffic, then released when I accelerated. Then suddenly I had a small knock noise in the bottom of the motor, 2 mechanics decided it was better to just replace instead of ripping apart and discover the problem and fix it for $5000 plus, instead of $1650 plus labor to replace with a used motor and 15k fewer miles. At the time of the motor swap, I had them replace the fan clutch to get rid of the code which it did. I now had the same problem you have. It was a Hayden clutch for $225, after discussing and letting them test drive they agreed it should disengage, options discussed and I decided on the AC Delco direct OEM for 400 and it works perfect, exactly like before but without the error code. My advice, get the AC Delco brand.
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