Hi all GMTNation. .I have a 03 gmc envoy 4.2 and I am getting a P1481 error code which is to due with the clutch fan speed sensor circuit malfunction. I had replaced my clutch fan a few years ago and everything was fine until recently I got this P1481 code but my clutch fan is still operating normally with no dash warning lights other than the code. I understand this is common and it usually is the clutch fan but can also be a wiring harness issue I would appreciate any help or comments on this issue ...thanks javindra
P1481 error code clutch fan speed sensor fault
- Thread starter JAVINDRA
- Start date
The GM 4.2L LL8 Engine Cooling System receives its heat transference via a unique Fan that drives Air through the various Radiators only when activated under certain conditions to eliminate the waste of energy it takes to constantly drive that Fan against the resistance of air. Thereby it sidesteps the unnecessary scavenge of the Energy of Rotation and Torque...and of course... reduces the Fuel required to overcome the effects of "Drag" on the Engine.
The system GM created is called the "Electro-Viscous Fan" and it is an absurdly complicated one. And like all complex solutions... this one is very far from being robust and is sensitive to a few different modes of failure.
As you can see in the attached image... the Specific Electrical Failure Point you are seeking out is an obvious one that happens when the Base of the loose PCV Tube used to protect the Wire Bundle communicating from its Connector near the Radiator down to the insert points deep inside of the Fan Motor Core from accidental damage in the front of the Engine from the Spinning Fan Blades or other debris, etc.. fails to do so.
With enough 'jouncing up and down' of that PVC Tube ...the Wiring Insulation gets worn away and the exposed (+) and (-) and (5) Volt Network Reference PWM Signal Wires can short out. So the problem of mere Friction of the Tube bouncing up and down featured in this early design was overcome with a mechanical modification in a later updated versions of this Fan:
If you'd like to see how complicated the diagnostics can get... electronically...watch Scanner-Danner trying to sort things out involving a related P1482 Code with his High End Scan Equipment and Diagnostic approach:
The system GM created is called the "Electro-Viscous Fan" and it is an absurdly complicated one. And like all complex solutions... this one is very far from being robust and is sensitive to a few different modes of failure.
As you can see in the attached image... the Specific Electrical Failure Point you are seeking out is an obvious one that happens when the Base of the loose PCV Tube used to protect the Wire Bundle communicating from its Connector near the Radiator down to the insert points deep inside of the Fan Motor Core from accidental damage in the front of the Engine from the Spinning Fan Blades or other debris, etc.. fails to do so.
With enough 'jouncing up and down' of that PVC Tube ...the Wiring Insulation gets worn away and the exposed (+) and (-) and (5) Volt Network Reference PWM Signal Wires can short out. So the problem of mere Friction of the Tube bouncing up and down featured in this early design was overcome with a mechanical modification in a later updated versions of this Fan:
If you'd like to see how complicated the diagnostics can get... electronically...watch Scanner-Danner trying to sort things out involving a related P1482 Code with his High End Scan Equipment and Diagnostic approach:
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The "Tube" and Harness will come connected to as part of the New Unit that you purchase... and while my preference is to rely upon GM OEM ACDelco Parts such as are illustrated from the linked images in my Photobucket... Other Members with more experience using the Alternate Acceptable Brands or even using the Later Model version of this Clutch-Fan can better advise you on what to purchase.
For the moment... I keep all of my old images of the Trailblazer 4.2L Engine Parts and Repairs here in a raft of many sub-albums that may in time, prove useful for reference via the next link. In a short while, I will be migrating the entire lot over to Flickr.com:
http://s557.photobucket.com/user/60dgrzbelow0/library/0000TRAILBLAZERENGINEREPAIR?sort=3&page=1
The Harness Plug mentioned by Scanner-Danner gets R&Rd at the upper left hand side of the Radiator and if you intend upon using any Test Equipment ...you can back-probe the individual wires there. If it comes down to cases and you decide to actually perform this R&R ... If you follow @Matt 's Excellent FAQ "How-To" ... then you cannot go wrong with this repair:
https://gmtnation.com/forums/threads/water-pump-replacement.17360/post-541514
But at the present time... Check for that possible Burned Out 10 Amp Fuse in the under-hood Fuse Panel in Position #20 and replace it if needed. If your engine is not exhibiting that "Terrible Roar" the P1482 Trouble Code presages...and If it is not broken and if your Engine Temperatures under varying conditions are nominal... then just as they say... "Let Sleeping Dogs Lie...".
For the moment... I keep all of my old images of the Trailblazer 4.2L Engine Parts and Repairs here in a raft of many sub-albums that may in time, prove useful for reference via the next link. In a short while, I will be migrating the entire lot over to Flickr.com:
http://s557.photobucket.com/user/60dgrzbelow0/library/0000TRAILBLAZERENGINEREPAIR?sort=3&page=1
The Harness Plug mentioned by Scanner-Danner gets R&Rd at the upper left hand side of the Radiator and if you intend upon using any Test Equipment ...you can back-probe the individual wires there. If it comes down to cases and you decide to actually perform this R&R ... If you follow @Matt 's Excellent FAQ "How-To" ... then you cannot go wrong with this repair:
https://gmtnation.com/forums/threads/water-pump-replacement.17360/post-541514
But at the present time... Check for that possible Burned Out 10 Amp Fuse in the under-hood Fuse Panel in Position #20 and replace it if needed. If your engine is not exhibiting that "Terrible Roar" the P1482 Trouble Code presages...and If it is not broken and if your Engine Temperatures under varying conditions are nominal... then just as they say... "Let Sleeping Dogs Lie...".
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Mooseman
Moderator
thanks Mooseman I have a four seasons unit in right now it seams to be operating ok now but I am now getting the dreaded p1481 error code but no other faults or warnings I don't know if I need to replace the clutch fan again (about 2yrs old) or I can repair the harness or just leave it and hope for the best winter is fast approaching... thanks Javindra
Mooseman
Moderator
You could take it out and check the wiring. It could have chaffed too. Also test it it to see if it works properly. It might have just bitten the dust again. We don't have any data on the Four Seasons brand. If it failed, then it should be put on the same list as Dorman.
How to test the electro-viscous fan clutch
How to test the electro-viscous fan clutch
Regarding your Question in Post #3:
For reasons that include the harsh environment, high temperatures and the poor weather conditions that can easily break down the normal, ‘Off The Shelf’ kinds of common wire that many might think acceptable… the only wiring for use in Automotive Applications is that which is expressly manufactured to counter those bad effects as mentioned. During my work on creating and making an unusual “Tech 2 PCM, BCM, TCCM, LGM, ETC... Bench Test Harness” ... I chose to purchase a reasonably priced, varicolored Automotive Quality Wire Bundle sold by wiregarage.com.
If you check out the dialogue and images in Post #8 on this matter... you will not be disappointed in making the same choice for practically any Automotive Wiring R&R; short of (pun intended) any need for really heavy amperage and voltage carrying usage within the vehicle. You will have no trouble in color matching single-color replacement wires and at a length of 10 Feet per Woven Copper Strand… these really should be long enough for whatever you might need during this repair or rebuild:
https://gmtnation.com/forums/thread...repaired-instrument-cluster.18272/post-553551
For reasons that include the harsh environment, high temperatures and the poor weather conditions that can easily break down the normal, ‘Off The Shelf’ kinds of common wire that many might think acceptable… the only wiring for use in Automotive Applications is that which is expressly manufactured to counter those bad effects as mentioned. During my work on creating and making an unusual “Tech 2 PCM, BCM, TCCM, LGM, ETC... Bench Test Harness” ... I chose to purchase a reasonably priced, varicolored Automotive Quality Wire Bundle sold by wiregarage.com.
If you check out the dialogue and images in Post #8 on this matter... you will not be disappointed in making the same choice for practically any Automotive Wiring R&R; short of (pun intended) any need for really heavy amperage and voltage carrying usage within the vehicle. You will have no trouble in color matching single-color replacement wires and at a length of 10 Feet per Woven Copper Strand… these really should be long enough for whatever you might need during this repair or rebuild:
https://gmtnation.com/forums/thread...repaired-instrument-cluster.18272/post-553551
Hello to all...
Good morning I need help... I have a 2002 GMC Envoy SLT. I don't have a scan tool with bio-direcrional controls, I couldn't get someone around me with Tech2 and I tried to get a Chinese copy but didn't work. And it was not for lack off communication with the PCM because my BlueDriver works just fine. I got a P1482, '81 & '84 so I replaced the clutch fan. I checked for continuity before installing it and inspected the wire connectors as well as the little cavity between the fan and the wires as indicated in one of the pics above. Once the replacement was done, I cleared the codes and a few weeks go by and the engine light goes on again but this time I only got a P1481. So this is what I've done but don't know how to proceed.
DMM
Set on DC/V-auto
Ground lead to battery ground and positive lead made measurements.
Connector 15326829
Pin A/BK/250 has a good ground
Pin B/WH/2368 = 11.16V
Pin C/GY/WH/2365 = 14.6V
Pin D/D-BU/2364 = 5.4V
Pin E/GY/597 = .217V
10A fuse
NOT hot at all times
Replaced fuse with known good and nothing
Cooling Fan Relay
Pin 2 = 3.7 mV
Pin 4 = 15.5 mV
Pin 5 = 1.4 mV
Pin 6 = 11.96 V
Visual inspection of the wire fron the fuse box to PCM seems ok. There's to many connections and didn't want to open them because I didn't know which one it was.
Good morning I need help... I have a 2002 GMC Envoy SLT. I don't have a scan tool with bio-direcrional controls, I couldn't get someone around me with Tech2 and I tried to get a Chinese copy but didn't work. And it was not for lack off communication with the PCM because my BlueDriver works just fine. I got a P1482, '81 & '84 so I replaced the clutch fan. I checked for continuity before installing it and inspected the wire connectors as well as the little cavity between the fan and the wires as indicated in one of the pics above. Once the replacement was done, I cleared the codes and a few weeks go by and the engine light goes on again but this time I only got a P1481. So this is what I've done but don't know how to proceed.
DMM
Set on DC/V-auto
Ground lead to battery ground and positive lead made measurements.
Connector 15326829
Pin A/BK/250 has a good ground
Pin B/WH/2368 = 11.16V
Pin C/GY/WH/2365 = 14.6V
Pin D/D-BU/2364 = 5.4V
Pin E/GY/597 = .217V
10A fuse
NOT hot at all times
Replaced fuse with known good and nothing
Cooling Fan Relay
Pin 2 = 3.7 mV
Pin 4 = 15.5 mV
Pin 5 = 1.4 mV
Pin 6 = 11.96 V
Visual inspection of the wire fron the fuse box to PCM seems ok. There's to many connections and didn't want to open them because I didn't know which one it was.
I'll say Good Morning as Well...and suggest that you Watch and Download the Scanner Danner Video I linked in Post #2 on this Topic as your Next Best Thing to having a High End Scanner. If you watch what he does and the steps he must take to Isolate the Control Circuit Failure, then you can replicate SOME of what his Tests are by using your Digital Multi-Meter with a slender Back Probe Pin to sneak into the Harness wires and compare what he shows on the Video with the results you acquire with your DMM Read-Outs.
Speaking of the use of an Oscilloscope ... Just to have the advantage of observing the Wave Forms after Analog to Digital Conversion for Low Voltage Network Diagnostics would be a boon in your present circumstances, so using one of these devices might work in your situation, too.
Since you have no access to a Tech 2 right now... One of these Combination 'Pico-Scope' & DMM for $90.00 would certainly extend your Diagnostic capabilities and somewhat emulate the Expensive Tools that Scanner Danner utilizes to hunt down this P1481-P1482 Fan-Clutch Mystery. . I'm not touting any particular one... but a majority of the Buyers of THIS thing seem fairly pleased with its versatility and performance for being a Battery Powered Hand-Held Scope that is under a Hundred Bucks.
Again... and as ever... Caveat Emptor (Buyer... Beware)
Speaking of the use of an Oscilloscope ... Just to have the advantage of observing the Wave Forms after Analog to Digital Conversion for Low Voltage Network Diagnostics would be a boon in your present circumstances, so using one of these devices might work in your situation, too.
Since you have no access to a Tech 2 right now... One of these Combination 'Pico-Scope' & DMM for $90.00 would certainly extend your Diagnostic capabilities and somewhat emulate the Expensive Tools that Scanner Danner utilizes to hunt down this P1481-P1482 Fan-Clutch Mystery. . I'm not touting any particular one... but a majority of the Buyers of THIS thing seem fairly pleased with its versatility and performance for being a Battery Powered Hand-Held Scope that is under a Hundred Bucks.
Again... and as ever... Caveat Emptor (Buyer... Beware)
ALLOSUN Oscilloscope Handheld Scope Digital Storage Meter and Digital Multimeter DMM 25MHz Single Channel - - Amazon.com
ALLOSUN Oscilloscope Handheld Scope Digital Storage Meter and Digital Multimeter DMM 25MHz Single Channel - - Amazon.com
www.amazon.com
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Nice 
thank you...
I got a follow-up question. What can I do when a fuse (that's ok) doesn't have power flow from the box itself. I check with the DMM and an incandescent test light. Does that mean replace or open the box?
thank you...I got a follow-up question. What can I do when a fuse (that's ok) doesn't have power flow from the box itself. I check with the DMM and an incandescent test light. Does that mean replace or open the box?
If the 10 Amp Fuse in the #20 PDC is NOT Blown...and the Metal Female Tines have NOT been spread too wide (There's a Bad Joke in there...somewhere...) AND your Wire Integrity from the Truck Harness to the PCM has proven continuity... I'm thinking that your are STILL facing the same problem of a Sketchy Short running somewhere between the Plug at the Radiator...and the Wire Harness Plugging into the Heart of the Electro-Viscous "Hockey Puck" at the center hub location.
If you have not gone to all the trouble of using a "Spy Glass + Bright Flashlight" examination of the wires nested inside of the Shielding Tube like THIS Guy does in this next video... you simply cannot discount a physical, 'friction wear' issue of why the Harness works GREAT for quite a while... and then it Shorts out all over again.
When it comes to running down "Electrical Gremlins" like these... in many instances... Checking for continuity when the Vehicle is NOT Running and Gyrating or Vibrating around enough to creates the conditions of this Weird Short...will display Good Continuity... that will turn out to be a Temporary Phenomena once those other action dynamics kick in.
You have not mentioned the Brand Name of the EV Fan-Clutch you Put in...but when it comes to these 17 Year Old SUVs... by now that harness has been getting the Hell seriously Beat out of it... and only an OEM Quality EVFC is called for. I know that this is a Hell of Lot of R&R for the sake of trying to get this ridiculously designed thing to function... but this next VOP (Video Original Poster) has The Right Idea on how to guarantee the Damned Thing will calm down and behave itself:
"The Simplest Explanation of ANY Problem... is nearly 100 % Correct.."
Occam's Razor
If you have not gone to all the trouble of using a "Spy Glass + Bright Flashlight" examination of the wires nested inside of the Shielding Tube like THIS Guy does in this next video... you simply cannot discount a physical, 'friction wear' issue of why the Harness works GREAT for quite a while... and then it Shorts out all over again.
When it comes to running down "Electrical Gremlins" like these... in many instances... Checking for continuity when the Vehicle is NOT Running and Gyrating or Vibrating around enough to creates the conditions of this Weird Short...will display Good Continuity... that will turn out to be a Temporary Phenomena once those other action dynamics kick in.
You have not mentioned the Brand Name of the EV Fan-Clutch you Put in...but when it comes to these 17 Year Old SUVs... by now that harness has been getting the Hell seriously Beat out of it... and only an OEM Quality EVFC is called for. I know that this is a Hell of Lot of R&R for the sake of trying to get this ridiculously designed thing to function... but this next VOP (Video Original Poster) has The Right Idea on how to guarantee the Damned Thing will calm down and behave itself:
"The Simplest Explanation of ANY Problem... is nearly 100 % Correct.."
Occam's Razor
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Mooseman
Moderator
I did...
If you actually read 🤔 the information you would know that the the issue is not the solid state relay but the fuse that feeds it, which its supposed to be hot at all times and it's not.
No need to write condescending massages Sir!
You want to write as if you have all the answers, NEWS flash you don't... you should at list write information that actually helps.
If you actually read 🤔 the information you would know that the the issue is not the solid state relay but the fuse that feeds it, which its supposed to be hot at all times and it's not.
No need to write condescending massages Sir!
You want to write as if you have all the answers, NEWS flash you don't... you should at list write information that actually helps.
Great post 👍
I saw a video about a similar issue, before I replaced it. I made sure to to check the wires for any damage and with a DMM for continuity. A service bulletin about this issue indicated that the cables should have an inch free of cover so I covered the rest with high-temp tape. I have an inspection cable with light so I'll double check and make any necessary corrections.
Mooseman
Moderator
Sometimes there's so much written that some details can be easily missed. Was just covering all the bases with the easier stuff first, hence the "dumb", or easy, question. Could have easily been the module that was shorting and blowing the fuse.
And I never purport to have all the answers but I do have a lot of knowledge, along with most of the other people here. Together we have ALL the knowledge.
I have to apologize... I've been very frustrated chasing this issue and got stuck on the "DUMB" comment. I can see now your point of view! I should have asked instead of having a negative response and for that I apologize.
Mooseman
Moderator
I saw this today very informative...👍
Mr. O. from "South Main Auto" diagnoses the electronic fan failure on a Trailblazer. Very informative a must see 👀...
Mr. O. from "South Main Auto" diagnoses the electronic fan failure on a Trailblazer. Very informative a must see 👀...
Printable Docs from that Cool Video:
...and some additional helpful GM Diagnostic Flow Chart for the EV Fan Clutch and a Connector Breakout for Relay #45 (Courtesy www.theroadie.org):
...and some additional helpful GM Diagnostic Flow Chart for the EV Fan Clutch and a Connector Breakout for Relay #45 (Courtesy www.theroadie.org):
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Mounce
Member
Came here to post that video, been watching him for a while, dude knows his stuff. Amazing what an oscilloscope can uncover throughout sensor, control, and linked bus diagnostics.
quote: "Pin C/GY/WH/2365 = 14.6V"
if I read the posted schematic correctly, I don't think that this jives.
Although at this time, I can't confirm but I do believe the fan speed has a PID in torque... iirc the list of gm pids available. If so, it might be a "cheap" method to get some further "on the fly" info.
if I read the posted schematic correctly, I don't think that this jives.
Although at this time, I can't confirm but I do believe the fan speed has a PID in torque... iirc the list of gm pids available. If so, it might be a "cheap" method to get some further "on the fly" info.
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