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Discussion Starter · #1 ·
Hello every one,

I am posting this to knwo if any one had such an experience, i recently bought my taurus 2001 SE, the engine RPM meter shows always at extreme high, in few days some times it starts to show correct value, then gets back to full.

there is no other issue such as transmission problem etc, i beleive the TSS is ok and only the problem might be from instrument cluster. i want to open it and have a look, before that i would liek to knwo if any one has such experience.

Thanks
razeen
 

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Discussion Starter · #5 · (Edited)
does it sound like the rpms are high or is it just the tach??
only the tech, no variation in actual, just want to know is it wired from sensor directly? or coming via communication? no fault codes present.

also i observed a new problem yesterday, my speedometer suddenly started to drop from 130km/hr to 80-90 and like jumping in between and got ok after some times, i was on a high way and 120 siren was alarming, when it got the problem the alarm still persisted and no change in actual speed. i like to open and check the instrument cluster, just wanna make sure i will be on the right place.

altogether i doubt some lose connection, but how can it go high when lose connection? may be some dry soldering on the PCB?
 

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Do you happen to have access to an oscilloscope? That would be the easy way tto test the tach as well as the tach signal to the PCM. The signal to the tachometer is provided via the PCM. The PCM will get the engine speed signal from the crankshaft position sensor (CKP).

I'd suggest you start by checking the signal to the tachmometer from the PCM. That line is could rule out the CKP and PCM very quickly. This will be a tan/yellow wire, terminal 48 at the PCM and terminal 8 at the instrument cluster. If you don't have an oscilloscope, you could probably get by with an AC voltmeter, checking for a steady voltage reading that changes with engine speed.
 

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hope that helps solve the problem. if not the cheapest fix is the old school put a picture in front of it so you never have to see it lol
 

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Discussion Starter · #8 ·
Do you happen to have access to an oscilloscope? That would be the easy way tto test the tach as well as the tach signal to the PCM. The signal to the tachometer is provided via the PCM. The PCM will get the engine speed signal from the crankshaft position sensor (CKP).

I'd suggest you start by checking the signal to the tachmometer from the PCM. That line is could rule out the CKP and PCM very quickly. This will be a tan/yellow wire, terminal 48 at the PCM and terminal 8 at the instrument cluster. If you don't have an oscilloscope, you could probably get by with an AC voltmeter, checking for a steady voltage reading that changes with engine speed.
thanks for the suggestion, i have an oscilloscope so let me follow what you say, i editted my post to tell i got a new problem with speedometer, the same way i can check? is the signal too from PCM?
 

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a jumpy speedo is a sign of a bad vss. has it been shifting normal? with a jumpy speedo and tach acting up it might be a pcm issue. ( i think both go to pcm then to the cluster )
 

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Discussion Starter · #10 ·
a jumpy speedo is a sign of a bad vss. has it been shifting normal? with a jumpy speedo and tach acting up it might be a pcm issue. ( i think both go to pcm then to the cluster )
Shifting is normal, so VSS maybe ok, so let me concentrate on whats from PCM
 

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if i remember right, if you have to replace the pcm you need to have it programmed to your car. if you dont it wont start.
 

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Discussion Starter · #12 ·
if i remember right, if you have to replace the pcm you need to have it programmed to your car. if you dont it wont start.
Thanks its a good information, any how its getting ok for few min once in every 2/3 days, so i only doubt any problem with connections. i will open it soon when i get a free time early morning, here its more than 40*C during day time & impossible to work parking under the sun :(
 

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it might be a voltage issue. just for kicks test your alt and battery. also look at the ground straps and make sure they are in tact and in good condition
 
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