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Topic: Tachomter fault (Read 730 times) |
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pinto
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TD04 on a galaxy manifold ? whooooooosh !
 
Posts: 474
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Tachomter fault
« on: Dec 22nd, 2009, 8:42pm » |
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Poor old cossie has been (for various reasons) parked up for 4 months now so on sunday I decided to just nip out and take a peek over her - battery as flat as a pancake 
Soooo.... 2 day charge later, i connected it up, turned her over WOT until i had oil pressure and then started her up - chain slap for about a second (but i guess thats to be expected - it is a cossie  ) before sweet, level tickover
All good  ... so I guess i should take it round the block to make sure its all ok.....
11 miles later and i'm in love again you forget just how good these things are !!! 
Anyway...i digress....
When i bought her from amigafan, it had a slight fault on the tacho - it consistantly read about 1k rpm lower on the dial than the true engine speed; this didnt bother me much at the time, but now its deteriorated to a huge extent - tickover to redline shows as 0 - 1k rpm on the clocks !
The VSS must be supplying correct data to the ECU as the shift speeds and kickdown are all good...so.... any advice where to start looking ?
thanks
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gozz
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Been around awhile
Posts: 3475
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Re: Tachomter fault
« Reply #1 on: Dec 22nd, 2009, 8:59pm » |
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Pinto.
Is the VSS not the vehicle speed sensor ? not too sure about the 24v,but most modern rev counters are energised by the alternator or the ignition pulse.
Someone is about to pop up and enlighten you I'm sure.
GOZZ.
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tlundkvi
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Ex. Scorpio 2.9 24V -95
Posts: 909
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Re: Tachomter fault
« Reply #2 on: Dec 22nd, 2009, 9:59pm » |
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Gozz is right, the VSS is just for measuring speed and used for various things but not rev counting. Did you check if the rpm error is just in the dash or does odb report the same error?
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pinto
Full Member
TD04 on a galaxy manifold ? whooooooosh !
Posts: 474
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Re: Tachomter fault
« Reply #3 on: Dec 23rd, 2009, 12:11am » |
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dash was a replacement unit just before i bought it (for this reason), and an OBD scan reveals no fault codes.
Alternator is functioning, so im unsure if this would throw a fault - only other thing i can think of is a fault on the EDIS 6 unit - i'll have to dig out my spare and try it.
Any other thoughts ?
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Tompion
Administrator
1997 2.3 Ultima estate.
Posts: 2918
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Re: Tachomter fault
« Reply #4 on: Dec 23rd, 2009, 12:54am » |
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On the ENGINE CONTROL 2-9 24V EFI IGNITION.pdf it looks like WH/BK wire from pin 2 of the eloctronic DIS module, also links to WH/RD pin 48 of the PCM.
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ABS multiplug wheel sensor pins MK IV or MK 20
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amigafan2003
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I'm a YaBB newbie!
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Re: Tachomter fault
« Reply #5 on: Dec 23rd, 2009, 7:39am » |
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For the record - I tried two didfferent dash unit in it trying to resolve the fault - both were exactly the same - so it's deffinately not the clocks at fault.
Hope you get it sorted - I'd love to know what's wrong with it!
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Jonnycab
Senior Member
Former owner of 2.3 Ultima Facelift saloon
Posts: 3900
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Re: Tachomter fault
« Reply #6 on: Dec 23rd, 2009, 10:12am » |
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Do you have the correct dash unit for a cossie ?
Also, as far as I know, the tacho works off a signal from the alternator.....so possible alternator diode fault 
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amigafan2003
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Re: Tachomter fault
« Reply #7 on: Dec 23rd, 2009, 11:35am » |
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Quote:| Do you have the correct dash unit for a cossie |
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It does (or did). I also tried another two clock units in it, both taken from a 24v Ultima - nothing changed.
Interestingly though - it always read 50% high when I had it. And when checking the type on the dash unit - it showed type 3 - i.e. 2.3 4 cylinder (for all three clock units). I can only guess the "type" isn't actually held as part of the clock unit but in the ecu/edis unit somewhere.
Another interesting fact is that the mileage didn't change on the clocks. i.e. I took a clock unit out of a 60k Scorpio and put it in my 130k+ Scorpio - the new clocks continued to show 60k. I always though the mileage was held in the ecu.
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pinto
Full Member
TD04 on a galaxy manifold ? whooooooosh !
Posts: 474
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Re: Tachomter fault
« Reply #8 on: Dec 23rd, 2009, 8:22pm » |
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Just read what i put and amiga was right - it did over-read, not under  my mistake lol
I think i'll start by looking at the multiplug to the DIS unit.
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Stixy
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I should know better
Posts: 414
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Re: Tachomter fault
« Reply #9 on: Dec 23rd, 2009, 8:59pm » |
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I thought all rev counters were the same but depending on which engine a wire is either grounded or ungrounded
pin23 plug C470b instrument cluster
( the wire is earthed through the engine loom via pin 8 multiplug C120 )
4 cylinder ungrounded
12v v6 grounded through an engine type code resister
24v v6 grounded
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amigafan2003
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I'm a YaBB newbie!
Posts: 972
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Re: Tachomter fault
« Reply #10 on: Dec 26th, 2009, 7:14pm » |
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You could be onto something there stixty.
Many a faulty has been traced to a faulty gound.
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