Quote:
Originally Posted by Vega$69
For the autometer tach to work you will to install a step up resistor and will set the dip switches to 4 cylinder 2 pulse.
|
http://www.autometer.com/media/2650-1563.pdf
Listed are the most common ways to hook up a tachometer signal wire to the most popular applications that tend to have an existing tachometer signal:
98 F Body: Pin #35 of the blue PCM connector.
99-02 F Body: Pin #10 of the red PCM connector.
LS equipped truck applications: Pin #10 of the red or green PCM connector (it will be either red or green, it will not have both). Not all trucks will have a tach signal wire.
97-98 Corvette: Pin #35 of the blue PCM connector, white wire. 99-04 Corvette: Pin #10 of the red PCM connector, white wire.
05-06 Corvette: Pin #48 of the blue PCM connector, white wire. 07-09 Corvette: Pin #48 of the black PCM connector, white wire. 04 GTO: Pin #10 of the green PCM connector, brown wire.
05-06 GTO: Pin #48 of the blue PCM connector, brown wire.
05 Cadillac CTS 5.7L: Pin #10 of the green PCM connector, white wire.
06-07 Cadillac CTS 6.0L: Pin #25 of the blue PCM connector, white wire.
All of the above will require the tachometer to be set for 4 cylinder, 2 pulse signal. If the tachometer fails to operate, there are several ways to handle this. Each
case may be a little different.
If the tachometer does not function:
You may check the original tachometer circuit. You can do this with a digital voltmeter.
Connect the positive lead of the voltmeter to the tachometer signal from the PCM.
Connect the negative lead of the voltmeter to a good chassis ground.
With your meter set on DC volts, start the engine.
Monitorwhatyouhaveatidle.Youshouldhavealowfigureth atrangesanywhere from 0.5 to 3.0 volts (and remains rather steady).
At a high-raised idle, it should be significantly more. As an example, if
you measured 1.0v at idle then at a raised engine speed you may see 3v, or more.
There is no spec for the amount of volts you will see. What you are looking for is an increase. For example: If you saw 1.0v and idle, then measured 1.1v with raised engine speed, then that signal is not changing, or operating normally.
If there is little to no activity, you may use a resistor to try and restore the weak signal. Installing the resistor: Use a 10K, 1/2 watt resistor (supplied in the LS Installation Kit). Solder one leg of the resistor to the tachometer signal circuit. Solder the other leg of the resistor to a 5v reference circuit.You may use a wiring diagram that pertains to your engine computer to determine what pin #, and wire color will be a 5v reference. *Hint: GM most commonly tends to use a solid gray wire for 5v reference, however you will still want to verify this with your wiring diagram, and a voltmeter set to DC volts. Do NOT use a 12 volt power supply or source for this. This may cause damage to the PCM.
10 7
Tachometer
If the PCM supplied tachometer circuit functions, but the tachometer does not: Take normal steps in diagnosing the tachometer. You may also try the tachometer on another vehicle. If it works on another vehicle, but not on your LS engine, then check the date code of the tachometer. Some older units (manufactured prior to 2007) may require a 5v calibration. All newer Auto Meter tachometers should not require this modification. Autogage tachometers may or may not function and CAN NOT be modified for 5v calibration.
If the PCM supplied tachometer circuit does not function, and you have already tried the pull-up resistor:: This will then require using a tachometer adapter. This is not uncommon when the computer (PCM/ECM) has been re-programmed or flashed. Some LS applications may have no wire for tachometer signal, or the computer may simply produce no tachometer signal. In this case a 9117 tach adapter will be required. The following details the steps required to install the 9117 on an LS engine.
Most commonly with original, and aftermarket engine wiring harnesses, the ignition coil power supply wire color is pink. Any applications using the adapter will be calibrated to 8 cylinder, 4 pulse.
Cut the pink power supply wire at each bank, prior to the coils splitting. This pink wire can be cut just prior to the wiring connector at the center of each valve cover.
The cut halves coming from the harness (not the halves going to the coils) will still have power when the key is on. Join the left and right bank power halves together. Splice these two power halves (now together) to the solid red of the 9117 adapter.
8
Now, join the coil-side cut halves together (left and right bank).
Splice these two coil halves (now together) to the red wire with a green stripe
of the 9117 adapter.
 Ground the black wire of the adapter to an engine ground.
Thegraywireoftheadapterwillbeyournewtachometersign al.Youdonot
want to try to cheat and use just one bank of coils, as the signal will appear
very erratic.
If the tachometer now functions well, but quits when above x-amount of RPM such as 4,000, then a shunt resistor will be needed. This is a 0.1 ohm, 3 watt resistor. Connect one leg of the resistor to the red adapter wire, and the second leg of the resistor to the red/grn adapter wire. This will allow some of the current to bypass the adapter, and still allow the tachometer adapter to function.