Picked up an 09 Trailblazer Lt a few months back,it has just a tad over 100,000 miles on it. The rpm gauge is driving me nuts...drops...fluctuates especially over 55mph,but like most women,she won't tell me what's wrong...not showing any codes when I scan the comp.....any help would be appreciated regarding the vehicle not women...I've given up there....stay safe!
RPM's
- Thread starter retiredcopper
- Start date
- Jul 22, 2015
- 2,724
Congrats on finding a low-mileage example. Not many left.
IIRC, the gauges have stepper motors, and they're not what one would call 'bulletproof', so that could be a factor.
You could hook up a OBD scanner and see if it tracks with the gauge or not (I'll bet it doesn't, or you'd easily detect it if the engine speed was really fluctuating that much). If any of the others appear flaky (stuck, dead), there are vendors who will replace / rejuvenate the cluster (or kits, if you're a DIY'er).
If you want to change lighting to LED (as the bulbs do burn out, as well), or repair the LCD output, that's the time to take care of everything in one fell swoop.
Just be thankful it reads in 'degrees', and not 'whatevers', 'nothings', or ' it's fines'
IIRC, the gauges have stepper motors, and they're not what one would call 'bulletproof', so that could be a factor.
You could hook up a OBD scanner and see if it tracks with the gauge or not (I'll bet it doesn't, or you'd easily detect it if the engine speed was really fluctuating that much). If any of the others appear flaky (stuck, dead), there are vendors who will replace / rejuvenate the cluster (or kits, if you're a DIY'er).
If you want to change lighting to LED (as the bulbs do burn out, as well), or repair the LCD output, that's the time to take care of everything in one fell swoop.
Just be thankful it reads in 'degrees', and not 'whatevers', 'nothings', or ' it's fines'
Mooseman
Moderator
Unless it's the actual engine RPMs that are all over the place, I would also suspect the stepper motor for the gauge. You could replace it or swap the entire cluster with one from a junker at a U-Pull yard however your mileage will be off.
These later years are not known for failing but just like @Reprise said, they're not bulltproof.
These later years are not known for failing but just like @Reprise said, they're not bulltproof.
The Sketchy IPC Tach & Speedo could be caused by something as simple as a loosely attached Blue IPC Harness Connector. Pulling the IPC is a fairly painless and straightforward action with plenty of YTs and Threads here on GMTN about doing the work.
Then... after spraying out the Pin Bus on the IPC MOBO Panel and also the Blue Connector with CRC Electric Solvent, plug the Harness connections back together. Look things over under the open Dashboard area too, for anything not too obviously viewable when it's normally all closed up.
Then without completely re-assembling everything, lay the IPC into the Dash area and take the SUV for a short spin on the road long enough to observe the behavior of the Tach & Speedometer. If it solves the issue(s)...Cool Beenz... re-assemble everything and no harm done.
But if not ...and you still plan on replacing all of the gauges from a Kit around this same time, trying this technique out will be one more thing to check off as a Routine Diagnostic effort to help narrow things down beforehand.
This On Topic video is also very interesting and instructive for DIY IPC Repairs:
Then... after spraying out the Pin Bus on the IPC MOBO Panel and also the Blue Connector with CRC Electric Solvent, plug the Harness connections back together. Look things over under the open Dashboard area too, for anything not too obviously viewable when it's normally all closed up.
Then without completely re-assembling everything, lay the IPC into the Dash area and take the SUV for a short spin on the road long enough to observe the behavior of the Tach & Speedometer. If it solves the issue(s)...Cool Beenz... re-assemble everything and no harm done.
But if not ...and you still plan on replacing all of the gauges from a Kit around this same time, trying this technique out will be one more thing to check off as a Routine Diagnostic effort to help narrow things down beforehand.
This On Topic video is also very interesting and instructive for DIY IPC Repairs:
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It's worth mentioning that at the places in the previous Video that the VOP is "wetting" down the Logic Board and Scrubbing down those damaged contact pads, in all likelihood he is using 99% Pure Isopropyl Alcohol.
This inexpensive Pro Solvent is available as an Amazon "House Brand" via this Link and should not be confused with the ordinary 70% version...which contains the contamination of Water...and this Stuff should NOT be used for Medical Purposes:
Please be advised that most professional electronic repair people have the good sense whenever working in close confines with these dangerous vapors and lead smoke when soldering to use a Booth Vacuum or Fan to minimize inhaling these fumes.
Isopropyl Alcohol can cause Liver Damage when merely inhaled in this manner; enough to bring on a Chemically induced Cirrhosis of the Liver... So Please... Be very cautious whenever using these Solvents for your DIY Projects.
This inexpensive Pro Solvent is available as an Amazon "House Brand" via this Link and should not be confused with the ordinary 70% version...which contains the contamination of Water...and this Stuff should NOT be used for Medical Purposes:
Please be advised that most professional electronic repair people have the good sense whenever working in close confines with these dangerous vapors and lead smoke when soldering to use a Booth Vacuum or Fan to minimize inhaling these fumes.
Isopropyl Alcohol can cause Liver Damage when merely inhaled in this manner; enough to bring on a Chemically induced Cirrhosis of the Liver... So Please... Be very cautious whenever using these Solvents for your DIY Projects.
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UPDATE:...took the dash apart and after vacuuming out all the spider and silver fish carcass',cleaned up the contacts and everything is working like a charm!...Thanks to all for the input!
They also make a 91% alcohol that you can buy in grocery stores and/or pharmacies. I use this all the time for dissolving things like the glue on your windshield after removing a registration sticker. It works MUCH better than the 70% stuff that is commonly used for antiseptic reasons.
Fun fact: The reason they make a 70% alcohol for medical use was that the 90% and higher stuff would evaporate too fast to kill germs. The 30% water addition caused the alcohol to evaporate slower, it needs to stay in contact with a germ long enough to kill it
