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Old 04-15-2011, 12:32 PM   #1
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Default Toyota Cops Fitted And Working But No Instrument Tach signal

94 1.8 NA running a MSPNP on HiRes 10g

After playing around with fitting some Toyota COP's i managed to get it started and running.
the Laptop picks up rev's fine (but this takes it from CAS rather than the Trigger from the four COP's) the instrument cluster Rev gauge doesn't move.

i started by wiring all the Tach lines (Four from COP's) to the pair of Tach on the car wiring harness, then i split the four COPs tach into 1,4 and 2,3 as that's the original firing pattern and soldered them to the wiring harness (one pair on tach wire).

using a multimeter i found that one tach produces around 2 volts and the other next to nothing, so i then cut one of the Cops tach from the harness that wasn't producing much in the way of signal. This caused it to rise to 1.2 volts.

i'm confused do i need to wire in a resistor so that the gauge can interoperate the signal or do i have some faulty COP's i would be grateful for any input.

i've read the post for the early 1.6 models so i'm curious to whether the same solution would work (putting a 1k resistor in with the tach wires from the COP's)

Or i believe you can get the MSPNP to send the signal to the instrument panel is this right?

thanks
Phil
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Old 04-15-2011, 12:38 PM   #2
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the tach wires should all be wire together and go back through the OEM wiring. You need all 4 for the tachometer to work correctly. 4 events per cycle = correct rpms.

You need to put a 1K 1/4 watt resistor in your diagnositics box from IG- to B+. This extra pull-up is needed to power the signal back to the dash.


The coil's tach out is bad if it has direct continuity to ground.
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Old 05-23-2011, 09:42 AM   #3
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thanks Braineack
i wonder if i have and faulty COP, because i've tried the above but still getting nothing from the Rev counter.

How easy is it to output the signal from the MSPNP to the factory gauge?
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Old 05-23-2011, 10:12 AM   #4
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makre sure none of your cops tach outputs are going to ground.

I have a coil that works fine, but I somehow sorted out that tach output, when testing it pulls to ground on that wire and effectively kills my dash tach. I had to replace it.


If the MSPNP already has the tachout circuit, you'd just need to wire it to the dash gauge input wire and turn on the function.
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Old 05-23-2011, 12:46 PM   #5
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me being a bit lame can i just clarify what you mean by "none of your cops tach outputs are going to ground"

the ground on each cop goes to the fire wall then wired back to the ground on the original harness.

thanks again.
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Old 05-23-2011, 12:47 PM   #6
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unplug your cop connector.
take a DMM, turn it to diode test mode so it chimes with continutity.
put one end on the tach out, and one on the ground and listen for a chime.
test each.
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Old 06-06-2011, 01:09 PM   #7
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sadly my DMM doesn't buzz but ran a Diode test on each wiring plug on the COPS and found one of them would flash up a figure for only a short second (each time you touch the DMM on) and the other 3 would display the same figure.

checked the signal on the B/W cable behind the instrument panel (the Tach) and it gets a 2.7 volt signal at idle.

I contact the DIYtune guys regarding the 94/95 MSPNP to see if it had a Tach output circuit already installed and the answer was yes:

"It has a tach output on 2I and 1F - two separate pins to accommodate a mid-year change in '95. Make sure Tacho Output Pin is set to X2 (JS0) under More Settings."

2i on the OEM harness already goes to the instrument panel so i moved it to 1F and made the changes in Tuner Studio. No joy :(

Any ideas on the volt figure the Tach receives?
Any chance i've f**ked the Tach gauge?

i will borrow a different DMM to buzz out he COP's wiring.

I'm off to the Ring in 4 weeks would love to know when to change gear

thanks
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Old 06-06-2011, 01:46 PM   #8
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unplug the coil that was different than the rest and idle car. Work now?
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Old 06-28-2011, 07:37 PM   #9
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well swapped the coils for a new set and now i get a signal on all four which is great wired them all together then to the two coil signal from OEM loom added the 1/4 watt resistor in the diagnostics box but still not enough to move the needle on the gauge.

any ideas of what the signal that the Tach gauge should react to? just so i can rule out if the gauge is faulty.

thanks
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