Tach Question
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Elder User
Joined: Mar 2004
Posts: 835
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Tach Question
hi all I was wondering where the Tach gets its Reading, Is it the CPS?. Mine is reading about 500 rpm high some times it bounces around,, I have an Aux idle controller so I can see what it is really at thats how I know it is off.
Thanks J
Thanks J
Cargo Master
Joined: Jul 2006
Posts: 2,756
Likes: 38
From: Nampa, ID
As long as there's nothing else wrong, (i.e. a bad VSS in the rear diff), replacing the CPS should be a step in the right direction.
There's a Ford recall on the CPS for the '97s. I had mine replaced and the engine seems a lot smoother and quieter. That's the input I got from my 12-year-old daughter.
Go to or call your local Ford dealer to see if they have your paperwork. You should receive a letter from Ford regarding the recall. My dealer had my printout before I got a letter from Ford.
Ford will replace the old (black) CPS with the new (gray) CPS for no cost. My dealer did not check for codes, so find someone to check and clear any codes. Ford will have to send back the old CPS, but you don't want that one as a spare anyway. If you want a spare, get the gray one. They're about $30 or less, depending on where you find one.
There's a Ford recall on the CPS for the '97s. I had mine replaced and the engine seems a lot smoother and quieter. That's the input I got from my 12-year-old daughter.
Go to or call your local Ford dealer to see if they have your paperwork. You should receive a letter from Ford regarding the recall. My dealer had my printout before I got a letter from Ford.
Ford will replace the old (black) CPS with the new (gray) CPS for no cost. My dealer did not check for codes, so find someone to check and clear any codes. Ford will have to send back the old CPS, but you don't want that one as a spare anyway. If you want a spare, get the gray one. They're about $30 or less, depending on where you find one.
Posting Guru
Joined: Oct 2011
Posts: 1,647
Likes: 1
From: Exton, PA
I realize that this is an old thread, but i've been doing some searching around for a solution to my eratic tach readings and came across it.
So, first - from reading other posts, i thought the black cps was the GOOD one and the grey one the junk one. i havent checked what my truck (96) has, but keep meaning to. can one of you experts out there post a reply here to clarify so that I and others don't get it backwards?
Now, related to my original search - my tach reads fine about 1/4 of the time, but drops out to zero about half the time and reads some fraction of the correct rpm the remaining quarter of the time. It seems like a classic poor connection problem somewhere, but havent looked into it in depth yet. the previous owner ripped the dash apart to install a plow setup on the truck, so my guess is that its the connector inside the dash. if i ever do fix it, i'll post my findings in case anyone else has similar problems, but in the meantime, I'd appreciate any experience out there with anything similar.
Thanks!
So, first - from reading other posts, i thought the black cps was the GOOD one and the grey one the junk one. i havent checked what my truck (96) has, but keep meaning to. can one of you experts out there post a reply here to clarify so that I and others don't get it backwards?
Now, related to my original search - my tach reads fine about 1/4 of the time, but drops out to zero about half the time and reads some fraction of the correct rpm the remaining quarter of the time. It seems like a classic poor connection problem somewhere, but havent looked into it in depth yet. the previous owner ripped the dash apart to install a plow setup on the truck, so my guess is that its the connector inside the dash. if i ever do fix it, i'll post my findings in case anyone else has similar problems, but in the meantime, I'd appreciate any experience out there with anything similar.
Thanks!
Lead Driver
Joined: Oct 2003
Posts: 8,476
Likes: 37
From: Madison, WI
If you can get your mitts on a data reader / scanner that will read our trucks (AF Scangauge, AutoEnginuity, Snap-On MT2500 or Modus), drive it around with it connected, set to display RPM, and when the dash tach acts up, see what the data feed says. If it goes haywire along with the dash tach, then the problem is "upstream" of the PCM -- CPS, connection there, connection at PCM. If the data feed reads normally, the problem is "downstream" -- gauge cluster, wiring to it, etc.
Posting Guru
Joined: Oct 2011
Posts: 1,647
Likes: 1
From: Exton, PA
Makes sense... Wouldnt the engine be acting up if it was one of the upstream problems, though? i've had the truck for over a year and haven't noticed any odd behavior (running rough, etc) associated with the tach drop-out.
However, i will run the idea of getting a scanner for the truck past the boss (wife). it won't happen any time soon, but might as well start laying the ground work for when its really needed.
However, i will run the idea of getting a scanner for the truck past the boss (wife). it won't happen any time soon, but might as well start laying the ground work for when its really needed.
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