Marcus Johnson 209 Diagnose never Guess
Gmasep (General Motors Automotive Service Education program)Graduate, ASE Master Certified, ASE Engine performance L1, Level 3 Engine Performance Mopar certified, Level 3 HVAC Mopar Certified, Level 3 Drivetrain Mopar certified, extensive experience in diag on Honda, Nissan, Mercedes,
I'm a young automotive technician who simply loves learning and evolving with the industry while always pushing myself to the next level as a professional automotive technician. Graduated from General Motors Automotive Technology program and did my internship at GM dealership and was full time employed at GM dealership as automotive technician. Then l received from God knowledge to switch brands. So I became a Mopar automotive technician and less than two years I am now factory Master Certified in multiple Mopar areas and working on becoming a specialist.
Tell us about yourself and your professional expertise, this will help you and others identify where you are today and want to grow to in the future!
Then verify system operating as intended using oem scan tool and temp measurement taken via N2.
"N2 WAVEFORM DEMO CAPTURE USING BOTH CHANNELS"
Recently had the opportunity to experiment with the N2 more and thought I would show how I use it to just as a first check tool when it comes to graphing capability compared to needing to grabbed a scope with higher sample rate speed and bandwidth. The wave forms I present here of exhaust camshaft signal in green obtained by back probing signal at the sensor and the red is ignition coil 1 control current ramp as reference point.
To give more information first check PIC- 1 as it explains what green waveform is showing with N2......PIC- 2 IS N2 CAPTURE ...PIC-3 IS KNOWN GOOD WAVEFORM...PIC 4 & 5 N2 physical setup of current clamp on pcm control wire to ign coil 1 and both sets of lead share com port and other back probe red lead on volts port.
Performed a quick visual check for dye from refrigerant leaks None seen at this time then used factory scan tool to check hi side psi level when turning on ac system no change in psi meaning that ac compressor is not coming on. Which stayed at 87 psi with ac button pressed and recirculation button pressed too. Bcm and pcm both see ac request signal and all temp sensors are reading correctly. If you are wondering why I have not checked clutch engagement this vehicle has a variable ac compressor (no clutch)
Already used bidirectional control to see cut on signal for ac compressor solenoid is present by this time I already have used meter to check all circuits are good and relay to send power to ac compressor and fuse protection are fine. Last step sucked down refrigerant just to make sure and system was indeed filled up to 820gram no leaks present as I thought. This took me 20mins to diag now since I had a few free minutes I grabbed N2 and used it's new air conditioning temp test which work really good to show bad performance and good performance when I install new ac compressor. Then I used the low amp clamp to verify even further that new variable compressor was operating correctly by measure a little over 1 amp current draw to solenoid in ac compressor. Where l then could see the pulse width waveform. N2 graphing speed lm was limited in this scenario but it was more than enough to verify repair complete!!
" G" talked about solenoids and how there controlled well I had a vehicle that I was currently diagnosing over the weekend which happen to have camshaft solenoid issue and it was one of those things l realized I never graphed a solenoid waveform before with the N2 in comparison to a small 1ch 2.5Ms max scope.
N2 using new alpha firmware in graphing set to 400 points at 64 sample under 256 range.
Scope in second pic at 3Ks at 5ms. Both waveforms taken from exhaust camshaft solenoid pcm control pin at idle on 13 chevy captiva.
Add this feature automatic conversion of 5v scale to psi to N2
this would make a crazy great addition to to N2's already cool features in sub-menus. Also if inside the sub compression menu there was a way to store up to 12 cylinder compression results then graph them for comparison all at once
As can be seen ch1 is red and also on aux voltage 1a=10mv also I believe I manually ranged up to 120amps
Waveform buffer was off for all tests. And at either 200 or 400 points for buffer depth window this test was done on a 4 cylinder 2021 Jeep renegade.
In the next pictures I add fuel injector #1 with ch2 in green voltage DC back probe this fuel injector with lead in volt port on N2 if I had switched ch 2 to manual I could have adjusted the waveform and matched it up to compression 1 and would show ignition timing of fuel injectors in sync with firing order that I place 4 cylinder specifications.
(Sidenote the initial rise/peak you see is the starter first engagement obviously and the once it's up and going the 4 pulses is each cylinder)Also this is good enough to do a quick inspection of fuel injection and crankshaft sync. For a wireless graphing meter it's pretty darn good. With a high amp clamp you may be able to squeeze a more detail wave form from N2 but I'm not sure.
Also I included a compression test of a 5.3ls gm engine too just to show it's possible and definitely can be done just resolution is different of waveform more peak instead of a curve.