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lost tach signal

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Old Jun 16, 2010 | 08:12 PM
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Default lost tach signal

i got a 99 ls1 pcm running a 6.0 in a 97 (lt1) style firebird. the tach has work previously. just swapped in a 99 pcm to see how it compares to the 01 one for the transmission.

anyways everything is working cept for the tach. the scan tool does see rpm, just nothing to the dash

any ideas? not really sure where to look. the rest of the dash does work. i do have to do a case relearn, would that affect the tach?
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Old Jun 16, 2010 | 08:53 PM
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Cam sensor and/or it's wiring... do you get a stumble, fart, or back fire every few startups? That's a sign of the same.
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Old Jun 16, 2010 | 09:34 PM
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Originally Posted by Frost
Cam sensor and/or it's wiring... do you get a stumble, fart, or back fire every few startups? That's a sign of the same.
haven't seen any of those

also....efilive does see rpm thru the scanner...just not getting thru to the tach...it worked last week and all i changed was the pcm

Last edited by steve40; Jun 16, 2010 at 09:45 PM.
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Old Jun 16, 2010 | 10:46 PM
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Right, the PCM is referencing the crank reluctor for RPM, so it will see it.

I may not be clear on your problem... is this an aftermarket tach tied into the harness' white RPM signal wire that is not working?
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Old Jun 17, 2010 | 04:44 AM
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it's the factory 97 dash
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Old Jun 18, 2010 | 09:05 PM
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ok, did a lil work today.

swapped my 01 pcm back in....tach works. put the 99 back in....no tach again. tried reflashing the cal and op system, no luck there too.

ended up going to the 01 and put in the 99 op and cal.

any ides on the 99 pcm, would suck to have the license wasted on what could be a good spare pcm to have around
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