b"So, weve established that the window is binding up intermittently, but were feeling lazy today. We dont want to do an hours worth of voltage and ground testing. We only need to see if all of the requisite thingsi.e., powers, grounds, and signals are there from the various computers to narrow down our fault, right? ,I\x03ZH\x03WUXVW\x032KPV\x03/DZ\x03\x0bDQG\x03ZH\x03VKRXOG\x0c\x03ZKLFK\x03states that voltage and current are inextricably tiedwhenrunningthroughaload,statedas \x0b(\x03 \x03,\x03[\x035\x0c\x0f\x03WKHQ\x03XVLQJ\x03FXUUHQW\x03WHVWLQJ\x0f\x03ZH\x03FDQ\x03leveragethisknowledgetoverifyandquickly FRQUP\x0f\x03WKDW\x03DQ\\\x03JLYHQ\x03FLUFXLW\x03KDV\x03ZKDW\x03LW\x03QHHGV\x03(or it doesnt) without a whole lot of testing.The Quick TestWe installed a current probe around the power)LJXUH\x03\x16\x1d\x032XU\x03]HURHG\x03DPS\x03FODPS\x0f\x03]HURHG\x03WR\x03WKH\x03H[LVWLQJ\x03FXUUHQW\x03RZLQJ\x03ZLWK\x03WKH\x03GRRU\x03RSHQ\x03DQG\x03WKH\x03window fuse at the CJB (Central Junction Box).ignition key on. This way, we only see the window current during testing.SeeFigure1forthelocationofthecurrent FODPS\x11\x037KH\x03UVW\x03WHVW\x03ZDV\x03WR\x03PHDVXUH\x03WKH\x03JRRG\x03ZLQGRZ\x03 Figure 4: A zoomed-in that worked properly so that we could characterize aview of our known-known good window circuit on the car.good power window Before we did this, however, we utilized a neat littlecircuit. We can see trick we use often when current testing. If you knowthat the window motor that there is only one current or actuation you want towas pulling around 4.5 amps. The sudden rise measure, you can prepare the vehicle for the test, openin current indicates WKH\x03 GRRU\x0f\x03 WXUQ\x03 WKH\x03 NH\\\x03 RQ\x0f\x03 DQG\x03 7+(1\x03 ]HUR\x03 WKH\x03 DPS\x03 when the window clamp to the existing running current (so that whenreached its stop, and actuating the window, this is the only current activityWKH\x03VXGGHQ\x03GURS\x10R\x03that the amp clamp sees).to zero amps is where the internal logics As we pushed the switch and the window moved, wecircuit interrupter (like recorded this scope capture and allowed the Auto-Closea circuit breaker of featuretotripthecircuit,whichallowsustomodelsorts) kicked in for the the normally operating circuits reaction to increasedauto window feature.current. As you can see in Figure 4, our good power ZLQGRZ\x03PRWRU\x03ZRUNV\x03MXVW\x03QH\x11\x03%XW\x03ZKDW\x03GLG\x03ZH\x03OHDUQ\x03from this? What key diagnostic information were we able to verify with noZLQGRZ\x11\x03:H\x03RSHUDWHG\x03WKH\x03ZLQGRZ\x03PXOWLSOH\x03WLPHV\x0f\x03QDOO\\\x03FDWFKLQJ\x03WKH\x03IDXOW\x03vehicle disassembly and very minimal testing? occurring on the scope. Figure 5 shows this test zoomed in for detail.1.3RZHUV\x03DQG\x03*URXQGV\x03DUH\x032.\x1e\x03WKHUH\x03LV\x03QR\x03PDMRU\x03YROWDJH\x03GURSSLQJ\x03RQ\x03 This vehicle simply had a window regulator cable binding in the regulator. the circuit. We know this because there is likely nothing at all wrong%XW\x03ZH\x03VDZ\x03LW\x0f\x03SURYHG\x03LW\x0f\x03DQG\x03TXDQWLHG\x03WKH\x03SUREOHP\x03TXLFNO\\\x11with the powers, grounds, or the modules drivers if the circuit can pull a nice strong 21 amps before the circuit reset. When we take the time to think about our approach to any diagnosis and 2. 7KH\x03WKUHH\x03FRPSXWHUV\x03LQ\x03SOD\\\x1e\x03WKH\x03VZLWFK\x03PRGXOH\x0f\x03%&0\x0f\x03DQG\x03WKH\x03'RRU\x03 apply what we know about the fundamentals of electricity and electrical Moduleareallworkingperfectly,bothCANLINmessagesandRZ\x0f\x03ZH\x03FDQ\x03RIWHQ\x03FUHDWH\x03WHVWV\x03OLNH\x03WKLV\x03WKDW\x03VDYH\x03KRXUV\x03DQG\x03KRXUV\x03RI\x03DW\x03physical bus signal-wise. Why? Because the windows move and thererate time. The same is true with network analysis, driveabilityin fact, any are no DTCs. electrical or electronic diagnosis at all.3. 7KH\x03ZLQGRZ\x03PRWRU\x03LV\x03HOHFWULFDOO\\\x03QH\x0f\x03DV\x03HYLGHQFHG\x03LQ\x03WKH\x03ZDYHIRUP\x11Now, by characterizing the known good window circuit, we know severalUsingcurrentmeasurementsandsomestrategytomodelthecircuits important things. allowed us to combine minimally invasive testing with an understanding RI\x032KPV\x03/DZ\x03WR\x03QDLO\x03WKLV\x03RQH\x03YLVXDOO\\\x0f\x03LQ\x03DERXW\x03\x15\x13\x03PLQXWHV\x03ZLWK\x03QHDU\x03]HUR\x03Back to the problematic side of the car. With our normally operating windowresearch, zero scanning, zero component removals, and zero breakage of circuit characterized and studied, we rigged up the same test for the faultybrittle and expensive Jaguar-only trim components.9 8"