Tach is jumping erratically?

1996 INFINITI G20
104,000 MILES • 4 CYL • FWD • AUTOMATIC
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CRUISING00
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Tach is jumping erratically.Will drop to zero and jump up to max and will continue. Does not happen at first start but after about 5- 10 minutes of driving. Do not notice any other signs and seems to run fine except for the jumping tach. Plan to do a full tune-up. Any other suggestions for this fix? tach is now not working at all.
Apr 8, 2008 at 8:37 AM
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SQM
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Hello,

It sound like a wiring issue with the tachometer circuit.
You likely have a lose ground or a wire with cracked insulation or corrosion.

I have attached the wiring schematics. You will have to trace the wires to find the issue.

Here is a helpful article on checking wiring harness:

https://www.2carpros.com/articles/how-to-check-wiring

Please let me know of any questions.
Thank you.
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Sep 16, 2021 at 9:01 PM