P2122

391 Views 21 Replies 4 Participants Last post by Ravalli Surfer, 4 mo ago

Ravalli Surfer

Discussion Starter · 5 mo ago

Well --- almost three years into code P2122, I finally found the trouble maker ... the sto-o-o-o-pid fan.

Naturally - after running an oscilloscope on the throttle rheostats and checking both resistance ramps and the mysterious "Null Point" --- I dismissed the foot throttle (APP) as any reason at all for the code; everything was right where it needed to be.

I suspected something was taking a hit off the 5V power supply from the ECM but I couldn't prove it since it was so intermittent ... the fan was never in my suspicion.

The P2122 OBD-II trouble, or fault, code means that the vehicle's on-board computer has detected low voltage in the throttle position sensor (TPS), which is usually below 0.17 volts. Code P2122 is defined as a Throttle/Pedal Position Sensor/Switch "D" Circuit Voltage is Low

....

... this is not the whole truth although it DOES run off the available 5VDC system coming out of the ECM.

The final clue was that the fan decided all on it's own to go into MAX-ON Mode.

The roaring told me all was not well and I got the P2122 instantly - it refused to clear until the fan speed dropped into a more-or-less normal RPM and I got to drive away at that point.

Here's the sketchy part ---> I cannot find a decent fan assembly and I have to install a brown box, house brand fan from O'Reily's.

I'll be posting the success or failure of this fan - and that might be fun to help debunk or support the nay-saying about off-brand parts.

(OK --> I didn't say to use off-brand spark plugs. That would be bad.)

/

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chem_man

· #2 · 5 mo ago

Congrats! If the fan you got at O'Reilly's was branded Murray, there is a very good chance that it was manufactured by Four Seasons/Hayden which I am sure you are aware are brand names of SMP.

My fingers are crossed for it being the cure!

Reactions: 1

Ravalli Surfer

Discussion Starter · #3 · 5 mo ago

chem_man said:
Congrats! If the fan you got at O'Reilly's was branded Murray, there is a very good chance that it was manufactured by Four Seasons/Hayden which I am sure you are aware are brand names of SMP.

My fingers are crossed for it being the cure!

Tomorrow --- if it's not actually snowing again --- I'll go out and change it.

I MAY have to drive my '86 K5 for a day or so until the melt-off.

chem_man

· #4 · 5 mo ago

I'm sure you won't like that.

Ravalli Surfer

Discussion Starter · #5 · 5 mo ago

chem_man said:
I'm sure you won't like that.

Oh no ---- I like to drive the K5. Maybe I'll try to find a way to duct tape a camera inside it anfd take it for a ride and video some of where I live.

It might make it to YT.

Reactions: 2

Schurkey

· #6 · 5 mo ago

Pretty sure my Trailblazer has an O'Reillys fan on it. Been so long I forgot where I bought it...

Louder at start-up than the previous fan. Whether that was because the previous fan was worn-out, I don't know. But either it's settled-down some, or I've gotten used to it. Doesn't seem to be as loud at start-up as it was.

I put that fan on when we still lived at the "old" house; we've been at the "new" house for over five years. So that O'Reilly's fan is maybe seven years old now.

Reactions: 1

Ravalli Surfer

Discussion Starter · #7 · 4 mo ago

Schurkey said:
Pretty sure my Trailblazer has an O'Reillys fan on it. Been so long I forgot where I bought it...

Louder at start-up than the previous fan. Whether that was because the previous fan was worn-out, I don't know. But either it's settled-down some, or I've gotten used to it. Doesn't seem to be as loud at start-up as it was.

I put that fan on when we still lived at the "old" house; we've been at the "new" house for over five years. So that O'Reilly's fan is maybe seven years old now.

Good t'know!

It's lightly snowing and that seems to affect my attitude about working on the TB today. But ---> I KNOW I have to, so this is rapidly not becoming an opt-out option, if you know what I mean.

Most fluidic driven fans - it matters not if it's also electric, if it has those clutches and a heavy-ish viscous fluid between them --- will make a lot of fan noise at cold start-up.

If you want to really hear fan noise at cold start, try a Hayden HD fan for a SBC! It'll scare you (Code: BROWN) the first time you install one. BT ---> DT!

Schurkey

· #8 · 4 mo ago

When it was me, I used the fan-clutch wrench set that's part of the O'Reillys loaner-tool program; the 36mm unit was what my '03 needed. Remembering this confirms that I bought the fan clutch at the Big O. Most likely a "Murray".

A bigass adjustable wrench works, too, but is cumbersome and substantially heavier.

Regular threads, not "reverse" threads. Seems to me that figuring-out the electrical connector, and the fan shroud were the worst parts.

Ravalli Surfer

Discussion Starter · #9 · 4 mo ago

Schurkey said:
When it was me, I used the fan-clutch wrench set that's part of the O'Reillys loaner-tool program; the 36mm unit was what my '03 needed. Remembering this confirms that I bought the fan clutch at the Big O. Most likely a "Murray".

A bigass adjustable wrench works, too, but is cumbersome and substantially heavier.

Regular threads, not "reverse" threads. Seems to me that figuring-out the electrical connector, and the fan shroud were the worst parts.

I've hardly ever used the B.A. wrench ..... instead I used an air chisel and just popped it on the top of the hex and spun it a bit - then it came off easily.

It never seemed to affect the water pump - although one would think so. But it didn't. Of course I never kept whacking on it --- if the air chisel didn't do it in just a couple of hits - it was time for matching Channel-Locks.

Ravalli Surfer

Discussion Starter · #10 · 4 mo ago

Well --- in the interest of honesty --- I STILL wanted to see it (the fan) malfunction ... and throw the crazy P2122 code --- which is NOT related to it in any but one way --- the 5V rail voltage!

In my testing --- (and not yet replacing) --- I noticed some bad juju on the 5V line in the APP, but ONLY when there was some notable hash on the Fan Speed SENSOR!

Hmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm.

How in Hell's Bells can a fan Speed sensor throw a P2122 code?
I would be happy if it was/were a P060E or sumpthin' like that.

This is odd. How much hash is also floating in the rest of the 5V line?

Imma should just change the fan and drive the sukkuh --- but I still want to KNOW .... ya know?

Schurkey

· #11 · 4 mo ago

Ravalli Surfer said:
but I still want to KNOW .... ya know?

Reactions: 2

Ravalli Surfer

Discussion Starter · #12 · 4 mo ago

More questions ----

Since the fan has locked into direct drive --- prolly the internal clutch assy jammed and locked it all together --- now I can run Cruise Control with no problems with no more P2122.

OK --- since we know the fan was going bad and was killing the 5V power - what about the fan is not reporting that it's locked into full speed and hasn't tripped a different code?

Is there a code for "overspeed" of the fan?

Poofinator

· #13 · 4 mo ago

There is, actually! P0493, which looks like it lines up with what you're dealing with. It's baffling that it's locked into full speed mode and not throwing other codes of any kind. Do any of the readers you have show any pending codes as well as fault codes?

Hmmmmm!

Ravalli Surfer

Discussion Starter · #14 · 4 mo ago

Nope --- no "pending codes" at al ... clean as a whitewashed outhouse when the preacher visits.

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Ravalli Surfer

Discussion Starter · #15 · 4 mo ago

UPDATE ----- all the news that's unfit to report ('cause Imma gonna yell!) !

Well --- as a sidebar: wondering what the Flat Rate for a 2005 TB EXT 4.2 ---- Clutch, Fan, Electric, Remove, Replace --- is.
Anyone know?

The fan's on and it works nicely.

No more codes? Well, we'll see.

I gotta make this a long list 'cause the series of events MIGHT be a clue to someone here --- surely NOT TO ME THOUGH [/Sam Kinison]

2nd day of driving after fan clutch replacement.
Went to meet a buddy downtown
Engine started at home and I drove away, slowly at first for about 3/4 mile
Entered highway, floored the throttle to "test" the transmission shifts - <ahem> drove to see my BMF buddy
Parked vehicle - had business inside the building at which I had arrived ---3 miles away
Finished business inside the building
Walked over to TB, opened door, threw in my briefcase
Inserted key in (what else?) the ignition keyhole
Started engine not touching anything but turning the key while standing outside of the vehicle, door open .... mind you ....
Opened window (old mechanic's trick so we don't get locked out of a running vehicle)
Closed door
Got distracted by a buddy taking a COVID-19 Warning sign off the door of the building ...15 minutes at the max helping him scrape double--sided tape off ...
Engine warmed up while running at a "normal" idle speed
I approached and opened the door ...
Slid into the driver's seat ('cause Imma gonna go get lunch) and what do I see????

REP/SEL

Uh huh! The ol' REP/SEL Code P2122 is back!

Wot? I didn't do nothing at all but start the vehicle and walk away from it and when I returned (it was idling) --- there it was --- dem damned lights again!

I could justify them coming on if I had touched the throttle --- but I never did!

Now --- lookie here --- I've scanned, Ohm'd out and oscilloscope'd that dual potentiometer system till my eyes bled and there's NO WAY they are defective.

BESIDES --- I NEVER TOUCHED THE THROTTLE WHEN I STARTED IT THIS TIME!

Anyone have any thoughts? The throttle assembly wass new when I got the vehicle -- my son installed it trying to make the P2122 go away.

Now it has a new fan - which OBVIOUSLY needed to be replaced anyway 'cause it was stuck Full-On. Everybody (well, maybe not everyone) said it was the fan.

PS ---> it did toss a P0495 before I changed it out. Once I got it out, I tried to turn it -- but it was, indeed: frozen.

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Poofinator

· #16 · 4 mo ago

...Wiring, maybe? Literally the only other things I can think of would be faulty part(s) or faulty wiring. If not faulty, maybe the connectors need to be cleaned?

chem_man

· #17 · 4 mo ago

Because of the P0495, I am wondering if the fan clutch you purchased is faulty.

Or, perhaps one or more of the female wiring terminals is not tight enough. See below for more details:

https://www.justanswer.com/chevy/6k2vu-chevrolet-trailblazer-ext-lt-what-s-alternative-reason.html

It might be worth a try to check for the loose female terminal.

Ravalli Surfer

Discussion Starter · #18 · 4 mo ago

The P0495 was with the old fan. The new fan has been quiet - code-wise, anyway so far.

I had wondered why there were no speed related codes from the old fan being seized into full-run all the time, and after I changed it, I went in to clear all the codes and it was there then --- I never saw it when the engine was running.

There was no SES or anything lit up on the dash either.

It may have been a "Pending Code" that hadn't hard-set yet. I dunnow.

At very cold morning startups, the fan roars - and it never did that before --- but it gets quiet after a few minutes and it only comes on when I'm in traffic or run the AC (which I actually DON'T use - after all, we really don't need cooling in Montana 'cause it's never hot enough to even break into a sweat.)

That said --> when I never touched anything but the key to start it that time it popped the P2122 code --- the pedal sensors were not in play ... so there's that to consider too.

Still crazy - after all these years.

chem_man

· #19 · 4 mo ago

OK. Well, all I can think of is maybe disconnect and then reseat the fan clutch connector. Or perhaps it was communicating with that Chinese "weather balloon" that went by you the other day.

Ravalli Surfer

Discussion Starter · #20 · 4 mo ago

I was 'way on the other side of Montana --- remember that this is --- what --- the 3rd or 4th largest state - east-to-west-wise?

If it came over here, I think I can hit something at 62,000 feet ... I hope so anyway.

Honestly - I'm kinda surprised that a whole lot of Montanans didn't stand outside and shoot at it.

Nah -- that would be West Virginia I think.

I never saw it except on TV.

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