Brandon Benes

Hey guys i need some help on my ls1 swapped 88 firebird. Im having troubles getting my tack to work. I have a 2002 "0411" pcm and an ls1 harness from pocket.

Ive already tried the pick up wire with a 680 ohm resistor with a fused switch to pin #10 and got nothing. Ive checked continuity on the cam wires to make sure i didnt nick anything putting the motor or wiring in and all came out good. i checked the voltage at Pin #10 on C2 of the PCM and got battery voltage, 12 when off around 14 when running. My scanner is showing rpm and the cam sensor is reading "high to low" and "low to high". I bought a spek 2 1/16 tach gauge to put on my hood, wired it up... still no tach. The tach is also wired to pin #10 of C2.

Ive pretty much exhausted myself trying to figure it out, i really dont want to by a tach adapter if i can get this to work. From what ive read the tach adapters are hit or miss on if it will read right. And if i have to buy a tach adapter what would be the best option to go with?

Thanks in advance.

johnw999

I posted this a while back;
https://www.thirdgen.org/forums/ltx-lsx/738047-e38-stock-tachometer.html

i have a 58x reluctor and an E38 ECM. My tach works fine. Speartech made my wiring harness, and they programmed my ECM. I think the solution was with the ECM tune. If not, my installer, Protree racing, knows how to hook up the tach.

Brandon Benes

Update. The signal coming out my PCM works when not hooked up to my factory Tach. PIN 10 is getting power from both sides. Coming out of the PCM and wire going to tach is getting power as well.

Ive tried the Automerter 9117 and am still not getting Tach to work. With the adapter connected to both OE Tach and aftermarket tach, it zeros out. When only connected to aftermarket it works.

Any input is greatly appreciated.

johnw999

five7kid offered some good info here:
https://www.thirdgen.org/forums/ltx-...ml#post6118042


Hope that helps.

88Greg

Get friendly with someone with an oscilloscope. Invaluable in situations like this. Nerds need love too !

QwkTrip

iTrader: (22)

That's what I did. I used an oscilloscope to check the frequency and voltage. Once I established that was okay then that led me to look at the gauges. Found that I was missing a ground screw in the back of my tach.

86White_T/A305

Keep in mind that the 411 pcm can be tuned for different tach output signals.So depending on what version stock tach you have..you can have the pcm tuned to match the tach signal needed for it to read properly.Aftermarket tachs usually have a switch or specific wires to be hooked up for either 4/6/8 cylinder tach input.On the transam dash..this is very important to know.I pulled out the cluster..and the tach out of the cluster to verify which tach i had since they are easy to swap.Then i had my tuner program the ecu for a v8 tach output and it worked...though my stock tach does drop off at high rpm..i have a secondary autometer with memory recall tucked away insight I rely on.

QwkTrip

iTrader: (22)

Mine does too. It works fine around town but is about 600 or 700 off at 7000 RPM. Always have to guess when to shift when running hard.

I have a set of Speedhut gauges mocked up in a gage pod but am on the fence whether I want to pull the stock gages. I really like the look of those old gages! Thinking of the shift light idea, too.

86White_T/A305

Lol I have a shift light and i can say..I never really push the car hard enough to trigger it.i shift early by instinct.My redline is 6700...If it hit 6200rpm while on a run would be abnormal for me.With the light work street action I get lately...I dont need to wind it out full tilt..yet.But I know a few cars around here that are itching to punch my ticket :P

scooter

iTrader: (11)

You may need to use something like the Dakota Digital tach adapter