Hammerhead1445

Finishing up a LS1 motor/ T56 tranny swap from 99 F Body to a 2004 Miata. Followed Flyin Miata's instructions for voltage step-up with 2.2 kohm resistor, but no tach response. Suspect their instructions are correct for a later model drive-by-wire crate motor and harness application like they use, but not quite right for my older F body PCM. Anyone already solved this problem? If not, anyone know what the waveform is that the Miata tach is looking for? Have also heard that there are different tach settings available in the LS1 PCM which could solve my problem (perhaps a "crank sensor" setting). I know there is a tach signal of some kind coming from the PCM because it will drive a shop test tach I had laying around, but wanted to use the stock Miata tach. Any help much appreciated!

aknovaman

iTrader: (7)

You dont need a pullup resistor for your application. Only needed for 2003-up PCM's.

Hammerhead1445

Have tried it with and without the pull-up resistor, but still get no response from the tach. checked pin-out and continuity of tach wire from PCM - all good. Stumped at this point, but still suspect a signal problem since the aftermarket tach I tried was reading what appeared to be about half the actual rpm. Does anyone know what the signal output waveform is from the 99 LS1 PCM (square wave, frequency, amplitude) and/or what waveform the 04 Miata tach is looking for? Thanks.

TomM

iTrader: (56)

What kind of aftermarket tach did you use? Most tachs need to be set to 6 cylinder, or maybe 4 cylinder, by the DIP switches on the back of the tach, depending on brand.

What kind of engine did your Miata have, i.e., how many cylinders etc.?

You can change the resolution on your tach output in the tune file, right now it should be set to six. It will take some trial and error but it can be changed......

T,

Dr Poofist

iTrader: (1)

Have you verified the PCM is actually sending out a signal? It should be 4 pulse iirc.

btlegacy

iTrader: (1)

Its going to be on the PCM side as the miata cluster is the same as all the other NB's. I am betting you need to change the signal output or check to make sure the wire is not damaged

Hammerhead1445

What's an iirc? New terminology to me.

Ranger50

IIRC= If I recall correctly.

Have you called Keith and asked this same question to him? Or even looked around a bit more on FM.com? I know they are doing an 04 MazdaSpeed Miata right now.

Hammerhead1445

Guess it's obvious I'm over 50 since I don't know all the online acronyms! I solved my tach problem and want to post it in case someone else makes the same mistake. The Flyin Miata instructions and the 2004 Mazda wiring manual correctly called out the green with orange tracer as the tach signal input wire to the Mazda tach at the instrument cluster. However, there are two green wires side-by-side in the connector at the cluster. They look like a green with yellow tracer and a green with orange tracer. After digging further I noticed on the diagram that there is no green with yellow tracer called out, but there is a green with red tracer wire (cruise control). Bottom line: I had mistakenly ID'd the tach wire (green w/orange tracer) as a green w/yellow tracer (no such wire) and had mistakenly ID'd the green w/red tracer (cruise control) as the green w/orange tracer. In my defense, the "orange tracer" tracer does not look orange at all - it looks yellow. After swapping the wires the tach works perfectly WITH NO PULL-UP RESISTOR! Thanks all for comments and maybe this'll help someone else.

btlegacy

iTrader: (1)

Great to hear you resolved it and good info for the rest of us

preluding