Tachometer going out.

2007LucerneCXL

Full Member
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Illinois
Buick Ownership
2007 Lucerne CXL. and 1995 Lesabre currently, past 1973 Riviera, 1968 Riviera
For those that don't know a FSM is a tool! All the pretty shiny things up on the garage pegboard don't mean sh*t if you don't know what you are doing. Ebay has full GM manuals along with some less expensive PDF DVD manuals, online services are available so check around for something that fits the budget and needs that you have.

On the forum there is a post for transmission service manuals free.
 

BuickGirlFromMars

Well-known member
1,373
330
83
Buick Ownership
1999 Buick Park Avenue Ultra (Supercharged)
This has literally been the single most helpful resource I’ve purchased (volume 1 and 2) and everyone here comes to me or respects me as some park avenue wizard, but truth be told most of my helpful or insightful wisdom comes from this.
a goodchunk is experience as an owner for 3 years now and fixing my car myself, but that only goes so far. The raw fruitful data is invaluable
1599478E-2692-40EE-8C89-F724ABF153C1.jpeg
I also own volume 1-3 of the olds/Buick manuals for the riviera and aurora which I’ve used to cross reference (they were written first, and you can tell Helms copy pasted the Rivera text when making park avenue because some periodic leftovers indicating Buick vs olds and other small quirks were left over from the other manuals)
 

BuickGirlFromMars

Well-known member
1,373
330
83
Buick Ownership
1999 Buick Park Avenue Ultra (Supercharged)
Another good tool is having the sense to know when you're in over your head and when to stop throwing good money after bad especially when you are at the mercy of repair shops. I'd be curious to know how much the OP has into his car.
Yes there is nothing wrong with admitting ones limits and acting accordingly(we pay experts in fields all through life for this very reason) OR we choose to learn to get where we need to be. But the OP is being slightly square peg round hole about the issue and ignoring some but not all what we say and that’s just leading him down a rabbit hole of what ifs. If you want to take a crack at this on your own you’ll need to go to step 1 and work with us but depending on the nature of the true issue may require hours of theory and gm computer systems research on a 93 to comprehend the relationship between computer and its wiring and it’s nodes. It’s all UART, which means less self diagnostics and less built in double checks or backups. The pcm is the master and it’s slaves, the sensors modules etc all report to it and that means each unit is wired not only to eachother but to the pcm. That means a crank sensor has wiring to the icm and the pcm, but may very well have wiring then to any early anti theft or the IP, etc.

It’s not impossible to understand but it just means that the possible sources of wiring faults has an increased physical presence than 97+

however , I know from personal experience that a faulty PROM chip ECM from a 90(maybe similar, maybe not. It’s obd 1) is very very capable of setting codes and behavior that mimics a plethora of problems unrelated and untrue in the real world. I had engine coolant, throtttle position, trans solenoid, cam sensor, o2 codes, some efficiency code etc when my pcm was bad and the car would run. It ran like shit and barely kept itself running.
Popped a different ecm with my PROM chip and instantly ran like butter and the only code was 41, which was for a magnet that was missing.
Does this mean the pcm is at fault? No but it shows that the ability of an un obvious cause to show symptoms all over the place is very real.

my advice, take stock of what you have replaced, what codes you have, the drive ability and how it runs In an explanation, what your mechanics have “said” is the problem, and write it up on a text document. Then, examine the relationship between your issues and the codes. Does it make sense, what doesn’t make sense, etc. if you feel boggled, I really think you should find a different and skilled mechanic but if you can grasp and understand a good chunk, work with us and don’t just ignore / run down rabbit holes. The car is surprisingly not complex and issues can be worked through rather dialectically(literally step by step in the fsm)
______________________________
 

Mad_Coachman

Active Member
659
173
43
Baldwin, New York
Buick Ownership
2002 LeSabre Limited
I just hate to pay other people to do a job that I can do myself at a fraction of the price and worse yet they mis-diagnose the problem or not do the job properly. It all boils down to what Clint Eastwood said in Magnum Force.


...or what he's willing to put up with time and money-wise.
 

Buickguy123

Buick Newbie
315
41
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Buick Ownership
Buick
The bolt shouldn’t have been reused but it’s gonna have to work. The tachometer relies on signals from crank sensor BUT LIKE WE SAID the wiring can be the issue and not the sensor or the tachometer physical stepper motor could be worn out you CANNOT know without looking at live data abs seeing if the reference circuit for the crank sensor comes and goes at the same time as the tachometer stops

if the rpm never changes according to the data and tach cuts, the connection between pcm and ip or tach is suspect. If rpm cuts with tech, sensor or wiring to pcm, or rare case pcm is suspect.
I think you are correct in that there is a bad wire somewhere? The Tachometer is now totally dead and the car starts but then stalled and died at operating temperature and new codes 18 and 41 were present. 58 and 66 too but I know those are there. I read where both the Cam sensor and the Crancase Position share the same wiring. I disconnected the battery and ran the car a bit at idle. Car running rough but running and no codes for now but still dead Tach. The shop that replaced the CPS and HB could have put in a bad sensor or installed it improperly? Both were changed in 2015 and the other in 2017. The shop said to bring it back in...but I may not...just dump it...shop will just want more money I suspect plus my new towing charge to get it there...or I could put a new $14 cam sensor in hope that works? Oh well...
 

Buickguy123

Buick Newbie
315
41
28
Buick Ownership
Buick
Yes there is nothing wrong with admitting ones limits and acting accordingly(we pay experts in fields all through life for this very reason) OR we choose to learn to get where we need to be. But the OP is being slightly square peg round hole about the issue and ignoring some but not all what we say and that’s just leading him down a rabbit hole of what ifs. If you want to take a crack at this on your own you’ll need to go to step 1 and work with us but depending on the nature of the true issue may require hours of theory and gm computer systems research on a 93 to comprehend the relationship between computer and its wiring and it’s nodes. It’s all UART, which means less self diagnostics and less built in double checks or backups. The pcm is the master and it’s slaves, the sensors modules etc all report to it and that means each unit is wired not only to eachother but to the pcm. That means a crank sensor has wiring to the icm and the pcm, but may very well have wiring then to any early anti theft or the IP, etc.

It’s not impossible to understand but it just means that the possible sources of wiring faults has an increased physical presence than 97+

however , I know from personal experience that a faulty PROM chip ECM from a 90(maybe similar, maybe not. It’s obd 1) is very very capable of setting codes and behavior that mimics a plethora of problems unrelated and untrue in the real world. I had engine coolant, throtttle position, trans solenoid, cam sensor, o2 codes, some efficiency code etc when my pcm was bad and the car would run. It ran like shit and barely kept itself running.
Popped a different ecm with my PROM chip and instantly ran like butter and the only code was 41, which was for a magnet that was missing.
Does this mean the pcm is at fault? No but it shows that the ability of an un obvious cause to show symptoms all over the place is very real.

my advice, take stock of what you have replaced, what codes you have, the drive ability and how it runs In an explanation, what your mechanics have “said” is the problem, and write it up on a text document. Then, examine the relationship between your issues and the codes. Does it make sense, what doesn’t make sense, etc. if you feel boggled, I really think you should find a different and skilled mechanic but if you can grasp and understand a good chunk, work with us and don’t just ignore / run down rabbit holes. The car is surprisingly not complex and issues can be worked through rather dialectically(literally step by step in the fsm)
Sound wisdom BGFM! However, I think after shoving $4000 into this beast the last like 3 years I need to see if I can het someone to give me $1000 bucks for it and hope they have your knowledge tools and TIME to fix the beast? Any mechanic is going to want too much for me to shovel more money into the thing. But if someone can good for them.
 

Buickguy123

Buick Newbie
315
41
28
Buick Ownership
Buick
I just hate to pay other people to do a job that I can do myself at a fraction of the price and worse yet they mis-diagnose the problem or not do the job properly. It all boils down to what Clint Eastwood said in Magnum Force.


...or what he's willing to put up with time and money-wise.
Totally absolutely positively right on spot on correct! In a sense it is not only the money but yet they cannot diagnose the problam and fix it or worse they make something worse.
______________________________
 

Mad_Coachman

Active Member
659
173
43
Baldwin, New York
Buick Ownership
2002 LeSabre Limited
Totally absolutely positively right on spot on correct! In a sense it is not only the money but yet they cannot diagnose the problam and fix it or worse they make something worse.
Time is money and I'd rather spend my time doing something enjoyable. Sometimes you just have to cut your losses and move on to the next one so you can fall in love all over again. (y) ;)
 
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