adjusting TPS pin 4 vs battery negative

[dmsantam]

Good day all, when i adjust the TPS, i use a digital voltmeter set to DC mode and measure between pins 1 and 4. Is there any reason why one should use pin 4 instead of just using the battery negative? As I understand it pin 4 should be 0v anyway. 

 

cheers,

[dirtrider]

14 hours ago, dmsantam said:

Good day all, when i adjust the TPS, i use a digital voltmeter set to DC mode and measure between pins 1 and 4. Is there any reason why one should use pin 4 instead of just using the battery negative? As I understand it pin 4 should be 0v anyway. 

 

cheers,

Morning  dmsantam

 

Yes, that (pin 1) is the TPS (idle to mid throttle) reference signal. The motoric uses the reference voltage to know the exact throttle plate opening.  That pin 4 is a reference LOW not a ground.

 

It does eventually return to battery negative but who knows the potential difference between the battery negative post & the Motronic low as the Motronic uses the engine ground stud for it's ground (known to have some resistance).    

 

There should also be an actual brown chassis ground wire attached to the L/H throttle body with a small bolt. As the throttle body is isolated with a rubber intake boot & non metallic rear boot.