RPM Reading Dropping Out

[blaze falconburger]

Every now and again the rpm reading drops out intermittently.  The signal comes from the car's ecu and also feeds the instrument cluster.  This does not drop out, and when I scoped the signal it is fine.  I've used various combinations of resistors and the input now has a nice 5v wave.  I am using firmware 2008-02.  I tried the latest firmware 2009-4-30 but that stopped the gauge from booting so reverted.

I cannot find a pattern, sometimes on idle, under load, decelerating.  Sometimes it does it a few times a minute, sometimes it can be a few minutes before it will do it again. Does anyone have any ideas why this is happening?

[ranz]

Many users have the same problem and it seems to me that problem is in the gauge. I have hooked up it same way that you do, signal is from cable ecu to instrument cluster and original RPM gauge works fine, also checked the signal with oscilloscope, no problem.

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It has been suggested that a slight pull-up resistor something like 100K between +12v and the RPM pin will solve the problem.
I'd be interested to know if anyone has tried this, and what the result is.

[ranz]

I'll try that tonight and post the results.

EDIT: no change at all, the reading is still jumpy.