DIY test of power output stage/ignition amp module N122 (long & BWW) - Page 2

turbo510 · 05-05-2012, 08:02 AM

The OP posted this over nine years ago, so chances are he's moved on. But good to know these archived posts continue to help.

JohnelP · 05-06-2012, 09:02 AM

Bosch released some scematics and some modules are not using JFETs, but BJTs.
So all the measurements algorithm does not apply fully. The transistors are not working as voltage controlled resistors, but cut-off/saturation (standard BJT power amplifier).

I would recommend to use the flashlight bulb/lamp method for testing and drive that to 3V and 4.5V

The described method was showing infinity resistance on all 4 channels. Reverse the polarity, some negative resistance was shown, because of DMM applied voltage and effect on the junctions. Obviousely, cyl 2 was always infinity, but that's a different story.

Tipically you need to buy multiple N122s, as you change them more frequently than the brake pads

My car had 2 N122 replaced....

05-06-2012, 09:02 AM	#12
JohnelP Audiworld Junior Member Garage is empty, add now Join Date: Jul 2005 Posts: 85	write up not applicable to all n122 though!!!! Bosch released some scematics and some modules are not using JFETs, but BJTs. So all the measurements algorithm does not apply fully. The transistors are not working as voltage controlled resistors, but cut-off/saturation (standard BJT power amplifier). I would recommend to use the flashlight bulb/lamp method for testing and drive that to 3V and 4.5V The described method was showing infinity resistance on all 4 channels. Reverse the polarity, some negative resistance was shown, because of DMM applied voltage and effect on the junctions. Obviousely, cyl 2 was always infinity, but that's a different story. Tipically you need to buy multiple N122s, as you change them more frequently than the brake pads My car had 2 N122 replaced....

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05-06-2012, 09:02 AM
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