Wierd PCM issue, looking for info
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Wierd PCM issue, looking for info Anyone know what the tach hookup wire (pin 10) does? Trying to diagnose my shift light problem I disconnected it, any to my surprise the car seemed to run fine (including my tach). I'm just wondering what that pin normally runs.
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Re: Wierd PCM issue, looking for info You need to splice into pin 10 off the red PCM connector, which is a white wire, and also make sure that the shift light is setup for a four cylinder ignition to operate properly.
Being the signal is low, setting to 8 cylinders will not trigger the light, thus the fix is to set it to 4.
The issue is that the "tach output" off the computer on the '98+ LS1 motor is the
same as that of a four cylinder ignition (2 pulses per crank rev).
Making this cylinder selection adjustment has made the light work, and no ill effects should be seen.
Being the signal is low, setting to 8 cylinders will not trigger the light, thus the fix is to set it to 4.
The issue is that the "tach output" off the computer on the '98+ LS1 motor is the
same as that of a four cylinder ignition (2 pulses per crank rev).
Making this cylinder selection adjustment has made the light work, and no ill effects should be seen.
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Re: Wierd PCM issue, looking for info Thanks for the reply! I guess I didn't make myself clear. The shift light was working fine for weeks then just died the other day. It lights up when I start the car but its RPM trigger is not working (like it gets no signal). So I started checking out the wires and put a multimeter to the PCM-10 wire where the shiftlight was connected, I got nothing. So for ***** and giggles I cut the wire, no ill effect. It's the right wire, it just stopped working. I'm wondering what else runs off that wire so I can verify my diagnosis (i.e. what should stop working if that wire is cut). My tach still works fine and the engine runs.. (shrug)
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Re: Wierd PCM issue, looking for info The other end of the wire goes to the ABS module. What the ABS module needs a tach signal for I'll never know... maybe it's used as an input for the cars with traction control.
