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Old 09-19-2007, 03:02 AM   #1
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Default Intermittant Tach Problem

What could be causing my tach to stop working occasionally?
Many times I've noticed a very slight "miss" or hiccup while driving and the tach then goes to 0. No SES light comes on, and the car continues to run normally. It always starts working again once I stop and shut the car off.
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Old 09-19-2007, 01:50 PM   #2
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Sounds like what Toastedoats went through.

I believe it was either a bad or dirty crank sensor.
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Old 09-19-2007, 05:04 PM   #3
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A bad or dirty crank sensor, as Bill noted, would be one of the things to check. That is the primary spot for the PCM to get the engine speed. This is the description.
Quote:
Description and Operation

TACHOMETER

The IPC displays the engine speed based on information from the PCM. The PCM converts the engine speed data to a 2 pulses/engine revolution signal. The IPC uses the engine speed signal circuit from the PCM in order to calculate the engine speed. The tachometer defaults to 0 rpm if a malfunction in the engine speed signal circuit exists.
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Old 09-19-2007, 05:07 PM   #4
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i know that on my series 1'*, the tach signal goes thru the icm, then to the pcm. is this true for ser 2?
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Old 09-20-2007, 09:56 AM   #5
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Originally Posted by samueljackson
i know that on my series 1'*, the tach signal goes thru the icm, then to the pcm. is this true for ser 2?
Yes.. I think it does.
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Old 09-21-2007, 02:25 AM   #6
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Should I try to clean it first, or should I just replace it while I'm there?
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Old 09-21-2007, 08:08 AM   #7
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I wouldn't replace it. First I'd be swapping the crank sensor. Based on your symptoms, that is what it appears is malfunctioning.

You can check the wires from the crank to ICM and ensure they are in good shape. I would not be swapping or replacing a $130ish dollar module because the signal passes through it.
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