Re: Tach problems

From: Bob Tom (tigers@bserv.com)
Date: Thu Nov 16 2000 - 10:19:02 EST


At 06:30 PM 11/15/00 -0500, you wrote:
>>From what I understand (I could be wrong) the Computer sends out the Tach
>signal to the actual guage, I'm guessing that the Computer gets it from the
>coil. This is why aftermarket tachs are more accurate and quicker, because
>they run straight from the coil... -miggity

That's right, if memory serves me ... been awhile since I examined this.

The rpm input signal in the '97+ Daks come from the coil to the PCM, then the
PCM sends, amongst other signals, an 'rpm' signal to the Central Timer Module
(located at the far end of the passenger-side dash) which, in turns, sends a
signal to the dash instrument panel.

The rpm signal in pre-97 Daks go directly from the coil to the dash instrument
panel. That's the reason why the dash gauges don't function when a '96 MP PCM
is used in a '97+ Dak ... the '96 MP PCM doesn't send any of these signals
to the
Central Timer Module (since it did not exist prior to '97).

Bob. Burlington, Ont., Canada.
'97 Dakota CC, 5.2L, 4x2, 3.92 SG, auto., 4265 lb.
Dyno: 231.2 rwhp 340.0 lb-ft rw torque
PB: 14.737 @ 91.75 9.364 @ 72.95



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