Frequency of faulty NEW engine rpm speed sensor G28 ?

[Mike Sylvester]

Are you sure your ohm meter is working and that you have it on the
correct setting?
That seems more likely than 2 bad G28s and a bad G4.

Mike

www.urq20v.com

> -------- Original Message --------
> Subject: Frequency of faulty NEW engine rpm speed sensor G28 ?
> From: "Jim Hollander at Hot Grips Mfg., Inc." <Jim at hotgrips.com>
> Date: Mon, November 22, 2010 4:29 pm
> To: <200q20v at audifans.com>
> 
> 
> My Vag-Com identified a faulty engine rpm sensor G28 on my '91 200 TQ 20v so 
> I ordered a new one.  Bentley Manual advised to check that ohms between 
> terminal 1 and 2 be approximately 1000 ohms, with terminals 1-3 at open 
> circuit, and 2-3 open circuit as well.  When I got the G28 sensor I was 
> curious and checked the new one with my ohm-meter and the reading on all 
> combinations between the 3 terminals was an open circuit.  I wondered if the 
> reason there was no ohms reading between terminals 1 and 2  might be because 
> the sensor needed to be positioned over the flywheel teeth to get a correct 
> reading.  But if there is a coil inside the sensor shouldn't there be 
> approx. 25 ohms at all times regardless of proximity to flywheel teeth?
> 
> I installed the sensor, and the reading did not change once it was in proper 
> position.  I plugged in the Vag-Com and still the code showed a engine rpm 
> sensor with no signal (bad sensor).
> 
> What is the frequency of a new G28 sensor being bad, any feel for this... 
> anyone?
> 
> My other question is:  There are two sensors (G28 and G4) on that aluminum 
> cast bracket that sits above the flywheel teeth.  Is the only difference 
> between them the color of the connector being tan or black, with their size 
> and ohms, functionality being identical otherwise?  In other words, if I 
> kept track of the connectors, can they be interchangeable?
> 
> Removing the old engine rpm speed sensor G28 was no picnic, and a bit of 
> abuse befell the other sensor  G4 (black wire end connector at the bracket 
> behind the engine on the firewall) next to it, because after installing the 
> new (bad) engine rpm speed sensor G28 my Vag-Com now showed both a bad 
> engine rpm sensor G28 and a bad ignition timing sensor G4 too.
> 
> It was very discouraging going from one a bad G28 to a bad G28 AND a bad G4 
> sensor.  But if these G28 NEW sensors often come in bad, then it all makes 
> sense.  Should I just order another G28 and insist on checking the ohms 
> between terminals 1 and 2 at the parts counter before accepting it? Of 
> course I will bring a copy of Bentley page 28.41 where the 1000 ohm test is 
> described.
> 
> Jim
> 
> 
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