NEED HELP Check Engine Light Blues

kcb58h

Original poster
Member
Dec 25, 2014
10
North Texas
My '04 TBlazer EXT LS 4.2L I-6 2wd 96k mi has a "CHK ENG" light that says the fan clutch needs to be replaced. It only lights up from time to time but this issue started over 2 years ago. The fan clutch is in fine working order insofar as that I've had no overheating problems with thousands of miles on it since the problem arose. The past two years I've gotten the TB inspected while the chk eng light wasn't lit up - no problem. Now I'm overdue for inspection and the light won't turn off. My mechanic just shrugs his shoulders and says it'll be $600. If anyone knows something I could try before replacing a working fan clutch, it would be much appreciated.


SUNP0005.JPG
Here are the error codes
P0495 Fan Speed High
P0135 O2 Heater Circuit (Bank 1, Sensor1)
Code0495 definition : Fan speed too high for a predetermined period of time.
 
Last edited:

Blckshdw

Moderator
Nov 20, 2011
10,665
Tampa Bay Area, FL
Sounds like you have an intermittent problem. As posted by another member, try checking for loose pins in the fan's wiring harnesses. There's the one on the outside of the shroud, as well as one inside the shroud, on the clutch itself. Getting inconsistent contact could be causing your problem.

My fan clutch died recently, wasn't engaging at all, but I did not have any overheating problems either, so it's quite possible yours also failed the same way. If you happen to catch it when the light goes off, you can test it yourself following the instructions from this thread.

 
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budwich

Member
Jun 16, 2013
2,027
kanata
without the codes, you aren't providing enough information for the forum to give you any good ideas as to how to solve your problem.
 
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TJBaker57

Member
Aug 16, 2015
2,897
Colorado
That code P0135 for your O2 sensor will most certainly need to addressed for your inspection. Have that sensor replaced then see if your check engine light goes away long enough for the inspection. The fan clutch issue may only pop up now & then.
 
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TJBaker57

Member
Aug 16, 2015
2,897
Colorado
Fan speed high is not likely caused by a poor connection as the 12 volt power is needed to engage the fan clutch. A poor or intermittent connection will result in the fan NOT engaging and thus you would not get a "fan high speed" error. Instead you would have a possible overheat condition and possible troubles with your AC which also depends on the engine fan.
 

Machoman

Member
Mar 10, 2014
123
We don't have mandated inspections where I live. I am not sure if this would work, but couldn't you clear the code right before you have the inspections?
 

budwich

Member
Jun 16, 2013
2,027
kanata
you can try replacing the relay. It appears that it is being "held up" longer than expected.... BUT it really isn't a relay, it is a "switch power FET" (solid state device). It is possible that it has a problem and is letting a "solid 12v" thru continuously at times (maybe when its hot) such that even though the pcm has commanded a lower speed, the "leakage" on the device is still to great to reduce the clutch "clamping" power and hence the fan is running at "equal to engine" rpm. Or it could actually be a bad clutch that is not allowing the fan to "slip". You can confirm by monitoring the fan speed (read and requested) in an app like torque or with a "good" scanner.

As mentioned, the o2 code likely needs addressing with probable replacement.... assuming the wiring isn't bad.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Try removing the fan relay and see if the fan freewheels as shown in the fan test thread. If it doesn't and still pulls a lot of air after 5-10 minutes of revving it at 2000 rpm, the clutch is likely defective by not disengaging, hence that speed too high code.

The O2 sensor likely needs to be replaced for the other code.
 
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kcb58h

Original poster
Member
Dec 25, 2014
10
North Texas
without the codes, you aren't providing enough information for the forum to give you any good ideas as to how to solve your problem.
Thank you, Budwich
Sounds like you have an intermittent problem. As posted by another member, try checking for loose pins in the fan's wiring harnesses. There's the one on the outside of the shroud, as well as one inside the shroud, on the clutch itself. Getting inconsistent contact could be causing your problem.

My fan clutch died recently, wasn't engaging at all, but I did not have any overheating problems either, so it's quite possible yours also failed the same way. If you happen to catch it when the light goes off, you can test it yourself following the instructions from this thread.

Sounds like you have an intermittent problem. As posted by another member, try checking for loose pins in the fan's wiring harnesses. There's the one on the outside of the shroud, as well as one inside the shroud, on the clutch itself. Getting inconsistent contact could be causing your problem.

My fan clutch died recently, wasn't engaging at all, but I did not have any overheating problems either, so it's quite possible yours also failed the same way. If you happen to catch it when the light goes off, you can test it yourself following the instructions from this thread.

Thanks for the overheating info - I am assuming it is working based on water temp dash gauge. I'll go back and take more than a cursory look under the hood. Thanks again.
We don't have mandated inspections where I live. I am not sure if this would work, but couldn't you clear the code right before you have the inspections?
MachoMan - I didn't know that clearing chk eng code was possible - my tech is not a stickler, he just wants to see an unlit check engine light when he inspects it. If I can just get the light to go out, I'm good to go. I'll google the how - to. Thanks.
 

kcb58h

Original poster
Member
Dec 25, 2014
10
North Texas
My '04 TBlazer EXT LS 4.2L I-6 2wd 96k mi has a "CHK ENG" light that says the fan clutch needs to be replaced. It only lights up from time to time but this issue started over 2 years ago. The fan clutch is in fine working order insofar as that I've had no overheating problems with thousands of miles on it since the problem arose. The past two years I've gotten the TB inspected while the chk eng light wasn't lit up - no problem. Now I'm overdue for inspection and the light won't turn off. My mechanic just shrugs his shoulders and says it'll be $600. If anyone knows something I could try before replacing a working fan clutch, it would be much appreciated.


View attachment 91142
Here are the error codes
P0495 Fan Speed High
P0135 O2 Heater Circuit (Bank 1, Sensor1)
Code0495 definition : Fan speed too high for a predetermined period of time.
SOLVED (Sort of) First of all thank all of you who took the time to offer assistance. Here's how it was resolved :
SUNP0007.JPGI got my mechanic to reset the chkeng light off. I drove the vehicle 80 hwy miles. The light did not come back on. I had it inspected and it passed. Inspector only mentioned a vapor leak probably triggered the chkeng light and to replace the gas cap but only with OEM part. He said that he sees that vapor leak issue a lot.
I have not replaced the gas cap yet but the chkeng light turned back on fifteen minutes later during the drive home from the courthouse where I got my new registration sticker.
Pure silliness. This makes no sense, but this is exactly how it went down. This inspection requirement is a joke.
I didn't get out of the problem on the cheap, however, my apartment impounded the unregistered TB before I could register it - $252.00
Have a nice day.
 

Mounce

Member
Mar 29, 2014
13,667
Tuscaloosa, AL
Yeah, don't replace your gas cap buddy. An evap leak has its own codes and none of those are the codes you had here. Kind of odd that he cleared the codes and didn't even look at what they were then said it was probably an evap leak. Sounds like he keeps his parts cannon loaded. Hope you take your car elsewhere for repairs and this guy is only your inspector to get the registration.
 

TJBaker57

Member
Aug 16, 2015
2,897
Colorado
I got my mechanic to reset the chkeng light off. I drove the vehicle 80 hwy miles. The light did not come back on

Doesn't matter how far you drive it. For a type B DTC like your P0135 it has to see the issue twice on 2 consecutive drive cycles to turn on the Check Engine light. The defect is most likely still there.

Screenshot_20191008-214518.png
 
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