Tachometer Issues - More added! PLEASE HELP - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


2000-2005 Discuss your 2000-2005 Bonneville SE, SLE, and SSEi Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

Reply
 
 
 
Thread Tools Search this Thread
Old 01-02-2006, 10:50 AM   #1
Senior Member
True Car Nut
Thread Starter
 
toastedoats's Avatar
 
Join Date: Sep 2004
Location: Fitchburg Ma _ToastedRice_
Posts: 6,837
Thanks: 0
Thanked 0 Times in 0 Posts
toastedoats is on a distinguished road
Default Tachometer Issues - More added! PLEASE HELP

Two days in a row last week while driving home from work, my tach randomly dropped to 0 rpm and stayed there until i restarted the car, then it was ok. I tried hitting the dash, and pushin the cluster in as suggested by custom88 in a similar thread, but it didnt help. When it dies, i can actually feel the engine do something, it almost feels like a shift, but i cant narrow down exactly what it is

If this was caused by a intermittant cam/crank sensor, i should also get an SES light aswell.. correct? No lights come on at all
toastedoats is offline   Reply With Quote
Old 01-02-2006, 11:51 AM   #2
Senior Member
Posts like a Camaro
 
Join Date: Apr 2005
Location: montreal, Canada
Posts: 1,108
Thanks: 0
Thanked 0 Times in 0 Posts
mike_peperni is on a distinguished road
Default

I dont think this a bad crankshaft sensor, mine was bad and i was running too rich, 13 mile/gallon and wasnt able to go WOT without loosing any power.

It happened to me last year, 2 time, the rpm was bouncing when i hit a hole on the road, but it never happened again.
mike_peperni is offline   Reply With Quote
Old 01-02-2006, 07:19 PM   #3
Senior Member
True Car Nut
 
Join Date: Oct 2002
Location: Groton, CT _NEBF 05, 06, 07_
Posts: 2,703
Thanks: 0
Thanked 0 Times in 0 Posts
markwb is on a distinguished road
Default Re: Tachometer Issues

Quote:
Originally Posted by toastedoats
If this was caused by a intermittant cam/crank sensor, i should also get an SES light aswell.. correct? No lights come on at all
I should think yes if crank/cam sensor malfunction a DTC would be set. Engine rpm is derived from the crank sensor via the PCM.
markwb is offline   Reply With Quote
Old 01-13-2006, 06:26 PM   #4
Senior Member
True Car Nut
Thread Starter
 
toastedoats's Avatar
 
Join Date: Sep 2004
Location: Fitchburg Ma _ToastedRice_
Posts: 6,837
Thanks: 0
Thanked 0 Times in 0 Posts
toastedoats is on a distinguished road
Default

Ok, i have 2 related events since starting this thread.

1. Last week, i was stopped at a red light, turns green.. I hit the gas and it hesitated for a second, tach went to 0, then the car stalled (the tach died BEFORE the car did)

2. Today, on the highway, tried to accellerate, tach dies, then the car hesitates for about 5 seconds, then smoths out.. tach sits at 0rpm until next start cycle.

I think my first two events of this occurance the car didnt stakll because the TC was locked, forcing the engine to spin a bit through the fault, and the same with today because i was on the gas trying to accelerate.

NO SES LIGHT
Had the car scanned, and no codes are stored
toastedoats is offline   Reply With Quote
Old 01-13-2006, 08:08 PM   #5
DINOSAURUS BOOSTUS

Expert Gearhead
 
BillBoost37's Avatar
 
Join Date: Mar 2005
Location: Enfield, CT
Posts: 41,391
Thanks: 0
Thanked 0 Times in 0 Posts
BillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of light
Default

I spoke to Toasty and mentioned he should test his coils and look over the ICM.

Mark..where does tach signal come from on 00+? I think it'* still derived from ICM???
BillBoost37 is offline   Reply With Quote
Old 01-13-2006, 08:30 PM   #6
Junior Member
Posts like a Ricer Type-R
 
Join Date: Aug 2002
Posts: 10
Thanks: 0
Thanked 0 Times in 0 Posts
willwren is on a distinguished road
Default

I know the tach signal GOES to the ICM, but I'm not sure if it comes from there and goes to the Tach. It'* obviously not the cluster or gauge considering the other symptoms. What about the possibility of an electrical dropout? Gauge loses power? So does the ignition and fuel at the same time?
willwren is offline   Reply With Quote
Old 01-13-2006, 09:52 PM   #7
Senior Member
True Car Nut
 
Join Date: Jun 2003
Location: Purgatory
Posts: 6,313
Thanks: 0
Thanked 0 Times in 0 Posts
PontiacDad is on a distinguished road
Default

Do you have a scanner? code reader is not good enough.

The signal is from the pcm, scan while the car is idling, does the scanner read engine rpm? If it does then the issue is with the tach or the wiring.
If it does not display any engine speed with the scanner and there is no ses light the pcm is failing.
The pcm gets its speed signal from the ignition control module which in turn gets it from the crank posistion sensor.

First thing though is to scan it with the tach dead for a starting point.
PontiacDad is offline   Reply With Quote
Old 01-13-2006, 09:59 PM   #8
Senior Member
True Car Nut
Thread Starter
 
toastedoats's Avatar
 
Join Date: Sep 2004
Location: Fitchburg Ma _ToastedRice_
Posts: 6,837
Thanks: 0
Thanked 0 Times in 0 Posts
toastedoats is on a distinguished road
Default

thanks for the input guys

will: If i had an electrical drop out shouldnt things in theory return to normal when the power came back up... and nothing else is affected by this phenomenon, just the tach and the hessitation

pdad: a scanner isnt exactly readily available to me, and especially since i cant narrow down when its going to happen, so far there is no link between occurances that i can duplicate the event.



Maybe i should buy an aeroforce guage now to watch the RPMS when it dies
and if the PCM is on its way out, then intense could get another order
toastedoats is offline   Reply With Quote
Old 01-13-2006, 10:18 PM   #9
Senior Member
True Car Nut
 
Join Date: Oct 2002
Location: Groton, CT _NEBF 05, 06, 07_
Posts: 2,703
Thanks: 0
Thanked 0 Times in 0 Posts
markwb is on a distinguished road
Default

Quote:
Originally Posted by BillBoost37
I spoke to Toasty and mentioned he should test his coils and look over the ICM.

Mark..where does tach signal come from on 00+? I think it'* still derived from ICM???
True. Low resolution engine speed (3X reference)-PCM Input-from the ICM The PCM uses this signal to calculate engine rpm and crankshaft position above 1200 rpm. Medium resolution engine speed signal (18X reference)-PCM input-The 18X reference signal is used to accurately control spark timing at low rpm and allow IC operation during cranking. Below 1200 rpm, the PCM is monitoring the 18X reference signal and using it as the reference for ignition timing advance. When engine speed exceeds 1200 rpm, the PCM begins using the 3X reference signal to control spark timing. Additionally, the IPC (Instrument Panel Cluster) uses the engine speed signal from the PCM to calculate engine speed. The tachometer defaults to 0 rpm if a malfunction in the engine speed signal ckt exists. Looking at a schematic, the PCM inputs the speed signal to the IPC. The crank sensor is where it all begins with the hall effect xdcers along with the 18X & 3X reference signals.
markwb is offline   Reply With Quote
Old 01-13-2006, 10:21 PM   #10
Senior Member
True Car Nut
 
Join Date: Jun 2003
Location: Purgatory
Posts: 6,313
Thanks: 0
Thanked 0 Times in 0 Posts
PontiacDad is on a distinguished road
Default

The gauge is a good idea and the pcm upgrade is fine too but theres nothing to say its your pcm at fault yet.

btw you dont need to mount the aerotech right away to start using it, just plug into your obd2 port and connect the posistive to cig lighter plug and your scanning.
PontiacDad is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Tachometer Failure sharpshooter3578 1992-1999 5 02-13-2008 01:48 PM
Ongoing List Of Issues. Added More Problems + Questions.... xDRx 1992-1999 7 08-25-2007 06:23 AM
tachometer Merrill'spontiac Lounge 1 08-27-2006 10:23 PM
Tachometer inaccurate... rm 1987-1991 3 10-06-2005 02:24 PM
Funky Tachometer macho_mike21 1992-1999 6 04-03-2003 12:32 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 01:34 PM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.