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Herd WebMaster
Forum Admin
USA
165 Posts |
 Posted - 04/13/2007 : 2:46:21 PM
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Impala SS Tachometer Wiring:
By Scott Mueller.
Impala SS Tachometer Wiring:
The best place to get a clean (filtered) noise free tach signal would be from the PCM connector pin A13. All B/F-car PCMs output the tach signal on this pin. You will need a terminal p/n 12084913 (for 20 ga. wire) to install in the PCM A connector, and then run the wire (the factory uses a white wire for this application and if you are diseased like I am the correct color is important <g>) over to the oval plug in the firewall behind the LH wheelwell. I removed this plug, slit it up from the bottom, ran the wire through it, and re-installed the plug back in the firewall for a water tight seal. Now you have a clean tach signal for any tach you might want to install.
In the '94-'95 manual the Red, Black, Grey and Blue connectors are referred to as connectors A, B, C, and D respectively, while in the '96 service manual they are C1, C2, C3 and C4. The tach signal is on pin A13 according to the '94-'95 manual designation, and C1-13 according to the '96 service manual designation. Both are really the same pin 13 on the same red PCM connector, only the designations were changed in the manuals.
Here is the color vs. naming translation for the PCM connectors:
Color '94/'95 '96
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Red A C1
Black B C2
Grey C C3
Blue D C4
An alternative to the PCM connection would be to use the negative coil signal. On a '94 or '95 Impala, there are three wires at the coil, two in a grey connector (pink/black and white/black), and one in a black connector (pink). The negative coil connection for a tach is available in two places. One would be the spare unused terminal location in the black connector (this is what I actually used when I originally installed my tach). The other is the white/black wire in the grey connector. The spare terminal in the black connector and the white/black wire are connected together inside the coil, so they represent the same signal, which is thenegative side of the coil.
Note that '96 Impalas use an improved coil with more spark energy and a different connector with only two wires (although there are three terminals in the coil, only two have wires connected to them). In the '96 models the two wires to the coil are pink/black and dark green. The dark green wire is the negative side of the coil, and could be used to run a tach.
Of course the '96 Impalas already have a tach running off of the A13 pin on the PCM. Unfortunately this signal is 1/2x the normal tach signal for a standard V8 tachometer, which will cause the tach in the Camaro cluster to read rpmx1/2 or half speed. Likewise if you run the F-car PCM calibration in a '96 Impala, the factory tach will read rpmx2 or double speed.
I am using the PCM signal to run the factory tach in my Camaro instrument cluster. Note that at least for '94 and '95 Impalas, this works the same whether I am running the B-car or F-car PCMs, as I have done it with both. If you are installing a Camaro instrument cluster in a '96 Impala, then you should use the coil signal to run the tach. If you are installing both a Camaro instrument cluster AND an F-car (Camaro) PCM in a '96 Impala, then the factory PCM tach signal can be used.
Finally, note that ALL Impalas have the tach signal available at PCM terminal A13. Scott. |
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Impala SS Tachometer Wiring
