Need advice. Have 2008 trailblazer, straight 6, 93K miles. Going down road at 45mph, sudden loss of acceleration in gas pedal, engine seemed to labor, then I heard a thud noise from the drive train, and suddenly the problem corrected itself and I drove on. It felt like the torque converter disengaged, then reengaged, if that makes sense. I used a good obd tester, and no codes were tossed, and the transmission tests all came out fine. I will change the tranny fluid, and filter, but I had thought I had already done that awhile back (not sure, too many vehicles). I thought I smelled something briefly also. I checked the dip stick and tranny fluid level was fine, and the fluid did not smell burned. Could this just be in need of new fluid and filter? Could it be one of the tranny solenoids, even though no codes were tossed? Thanks for any help.
Thud Noise After Loss of Power
- Thread starter kenzoil
- Start date
In addition to having Low Transmission Fluid determined with observing the 4L60E Dip Stick with the Engine Running and in PARK, on occasion... a Fractured Ceramic Core inside the CAT-Can might suddenly drop down and make a disturbing noise and also act to obstruct the Exhaust Gas Flow out the Tail Pipe, bogging down Engine Performance.
If you have had an excess smell of Gasoline, a Flashing CEL lately or persistent Misfires and P0300 (or P0301-0306) or P0171 Codes... these could be symptomatic of having a Clogged CAT. The Diagnostic for any such Core Damage is performed in a non-invasive manner as follows:
(1) Lay a LARGE Piece of Fresh Cardboard under the Passenger Side of the SUV and lay on your back adjacent the CAT-Can ...with the KOEO and with the Parking Brake SET.
(2) Using a "Dead Blow Hammer" Very Lightly *Tap-Tap-Tap* along the underside of the CAT-Can and listen for the sound of "Pocket Change being Dropped into a Ceramic Bowl" or any similar kind of sounds. DO NOT BEAT OR POUND HARD UNDER THERE!
(3) If the Re-Bound Energy of these Light Taps causes a Return Noise as mentioned of the Broken Pieces of the Rare Earth Metal Impregnated Ceramic Honeycomb bouncing loosely off the bottom inside of the CAT-Can, then your CAT will need to be replaced with an OE Quality version; preferably an OEM one from GM.
(4) An Alternate Method for Diagnosing a Blocked CAT-Can is to Pull the Upstream O2 Sensor and driving the vehicle briefly at and above 45 MPH to see if the Power and Normal Shifting returns. Use a Recommended O2 Socket for this Purpose, else damaging the Metric Hex Top of the in-dwelling O2 Sensor may make matters WORSE if the Flats get Buggered Up.
If you have had an excess smell of Gasoline, a Flashing CEL lately or persistent Misfires and P0300 (or P0301-0306) or P0171 Codes... these could be symptomatic of having a Clogged CAT. The Diagnostic for any such Core Damage is performed in a non-invasive manner as follows:
(1) Lay a LARGE Piece of Fresh Cardboard under the Passenger Side of the SUV and lay on your back adjacent the CAT-Can ...with the KOEO and with the Parking Brake SET.
(2) Using a "Dead Blow Hammer" Very Lightly *Tap-Tap-Tap* along the underside of the CAT-Can and listen for the sound of "Pocket Change being Dropped into a Ceramic Bowl" or any similar kind of sounds. DO NOT BEAT OR POUND HARD UNDER THERE!
(3) If the Re-Bound Energy of these Light Taps causes a Return Noise as mentioned of the Broken Pieces of the Rare Earth Metal Impregnated Ceramic Honeycomb bouncing loosely off the bottom inside of the CAT-Can, then your CAT will need to be replaced with an OE Quality version; preferably an OEM one from GM.
(4) An Alternate Method for Diagnosing a Blocked CAT-Can is to Pull the Upstream O2 Sensor and driving the vehicle briefly at and above 45 MPH to see if the Power and Normal Shifting returns. Use a Recommended O2 Socket for this Purpose, else damaging the Metric Hex Top of the in-dwelling O2 Sensor may make matters WORSE if the Flats get Buggered Up.
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Thanks for the input. Upon further testing with my obd tool, under LGM (liftgate module), I found a number of codes that were stored in history. P1902 P0023 P1910 C1013 C1513 C2013 C2513. I have NO check engine light on, and it never came on. Have no idea why these codes come under the LGM heading. Any clue??
Mooseman
Moderator
P1902 (exhaust temp sensor) does not exist on this platform
P0023 (exhaust cam actuator B) should not be on this engine since there is only one actuator for the one camshaft.
P1910 (gear selector module) no such module in this platform
C1013, c1513, c2013, c2513 no such codes exist
You sure you weren't looking at a saved scan from another vehicle? The P codes usually throw a CEL.
P0023 (exhaust cam actuator B) should not be on this engine since there is only one actuator for the one camshaft.
P1910 (gear selector module) no such module in this platform
C1013, c1513, c2013, c2513 no such codes exist
You sure you weren't looking at a saved scan from another vehicle? The P codes usually throw a CEL.
Don't know what to say. I should say I have the tire inflation TPMS light on in the dash, but that has been on forever after changing over tires between seasons. It's a rather new obd tester. I believe I only used it on the trailblazer. Is there a good link to only Chevy Trailblazer base, 6 cylinder out there? So much junk on the internet.
Mooseman
Moderator
Which scanner do you have? We have found that the simplest and best is ELM327 bluetooth with Torque Pro on Android for powertrain (P) codes. For all the other codes, there is the free Chevrosys app and for a few bucks the Car Gauge Pro app. And for deeper diving, @TJBaker57 can instruct on command line type of scanning to get more stuff.
Mooseman
Moderator
After clearing codes, I am still getting code P0023 show up (exhaust camshaft position actuator solenoid valve control circuit bank 2). I suppose I should replace this solenoid, but where is Bank 2 on this Vortec 4.2 straight 6 engine?
So from all the videos I see on-line replacing this solenoid valve near the power steering pump, is that what would be called bank 1 if a code was tossed?
You've got to figure out WHY that particular errant code is popping up for the GM Atlas LL8 4.2L Engine ...when it should only be appearing on an LS style V-8 Motor...if at all. For example... What other drive-ability symptoms or possible related codes are showing up in your Persistent, Historical Trouble Codes? Do you have a Flashing CEL on the IPC?
One other possible issue concerns whether or not your PCM and BCM Calibrations are UP TO DATE. Having either a VXDIAG NANO or a GM "Clone" MDI (MDI-2) or a Legacy Tech 2 or even an Autel MaxiDAS DS708 Scan Tool capable of Reading and Writing as a Pass Thru Device of the latest (Last) versions for your particular YOM Trailblazer off of a Legacy TIS2000 Laptop would give you the chance to check that issue out. Having "The Last, Best Calibration" installed inside of your PCM can often solve a multitude of sins.
One other possible issue concerns whether or not your PCM and BCM Calibrations are UP TO DATE. Having either a VXDIAG NANO or a GM "Clone" MDI (MDI-2) or a Legacy Tech 2 or even an Autel MaxiDAS DS708 Scan Tool capable of Reading and Writing as a Pass Thru Device of the latest (Last) versions for your particular YOM Trailblazer off of a Legacy TIS2000 Laptop would give you the chance to check that issue out. Having "The Last, Best Calibration" installed inside of your PCM can often solve a multitude of sins.
The only two current codes that pop up at this point are P1902 and P0023. In history the code that pops up is P1910. Apparently, both of those codes should not appear for the Vortec 4.2L. I'll see about getting an update for my scanner and try again.
Mooseman
Moderator
I rechecked and this code does not exist for the 4.2 (should be only bank 1). Either there's something wrong with your scanner or possibly something with the PCM giving false codes. If I'm not mistaken, this same PCM is also used with V8 engines so maybe something wrong in the PCM.
If this were me, I'd find a used good PCM at a pick-n-pull cheap and swap it out.
Edit: Posted at the same time. Good idea on the update for your scanner. Try this first before the PCM swap.