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1989 Mercedes Benz 300se Tachometer & Speedometer

Tiny
BRYAN321
  • MEMBER
  • 1989 MERCEDES BENZ 300SE
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 185,000 MILES
About a year ago my tachometer quit working after the engine was revved while driving and the transmission shifted abruptly.

A few months ago my speedometer quit working too. I have the web driven Mercedes Service manual from MB but I have been unable to find any information in the manual on how to trouble shoot or fix either problem.
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Thursday, February 26th, 2009 AT 4:10 PM

7 Replies

Tiny
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  • MECHANIC
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If it was me I'll start with the speedometer impulse transmitter on left rear of transmission.
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Thursday, February 26th, 2009 AT 4:17 PM
Tiny
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What about the Tach? I saw on a parts website that there are speed sensors on the front wheels. Are these for the ABS system? Not the speedometer.
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Thursday, February 26th, 2009 AT 4:21 PM
Tiny
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Does it have a vehicle speed sensor I've looked couldn't find one-check that if it has one.

The ABS rpm sensor is at the front and back of the vehicle and also it has its on computer
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Thursday, February 26th, 2009 AT 4:35 PM
Tiny
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Just got off the phone w MB dealership. He could not find the speedometer impulse transmitter as a stand alone part. He mentioned a transmission harness. He also mentioned that the tachometer runs off of an engine componant, cam, crank, alternator. Do you have any ideas what runs the tachometer?
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Thursday, February 26th, 2009 AT 4:50 PM
Tiny
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The CPS gives the computer the piston postions and engine speed, CMH synchronizes the injectors and what stroke its in
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Thursday, February 26th, 2009 AT 4:59 PM
Tiny
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What is CPS & CHM?
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Thursday, February 26th, 2009 AT 5:06 PM
Tiny
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CPS --Crankshaft Position Sensor

CMH--Camshaft Position Sensor
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Thursday, February 26th, 2009 AT 5:16 PM

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