Auto Service Professional

OCT 2018

Magazine for the auto service professional

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Page 27 of 69

26 A S P O c t o b e r 2 018 the CKP sensor and the PCM. e problem went away. e obvious cause was a wiring problem in the sensor circuit from the CKP sensor and the PCM. at sums up this article this article on igni- tion waveform diagnostics. e more disciplined you are in consistently scoping out secondary ig- nition, the quicker and easier it will be to detect causes of engine misfires. ■ I g n i t i o n W a v e f o r m D i a g n o s t i c s Figure 24: 2001 Chevy Express van (loss of secondary) On my inspection of the tip of the Chevy Express crank sensor, I found no interference. Shown here is a secondary ignition waveform during the misfire symptom. Notice the loss of the point of primary turn-on. COURTESY OF ROBERT BOSCH LLC Figure 25: 2001 Express van (loss of CKP) Notice the waveform of the CKP signal. You can see the intermittent dropouts of the CKP signal. COURTESY OF ROBERT BOSCH LLC Figure 23: Coil current (carbon tracking) Notice the coil amperage waveform. After the point of primary turn-off, notice the erratic transfer of energy from primary into secondary. This problem is very common in taking out the primary drivers inside the PCM as in Ford and Chrysler systems. Figure 22: 2003 Honda Odyssey (after fix) Notice the waveform after replacing the number 4 coil. COURTESY OF ROBERT BOSCH LLC Bill Fulton is the author of Mitchell 1's Advanced Engine Performance Diagnostics and Advanced Engine Diagnostics manuals. He is also the author of several lab scope and drivability manuals such as Ford, Toyota, GM, and Chrysler OBD I and OBD II systems, Fuel System Testing, many other training manuals in addition to his own 101 Lab Scope Testing Tips. He is a certified Master Technician with over 30 years of training and R&D experience. He was rated in the top three nationally in Motor Service Magazine's Top Technical Trainer Award and has instructed for Mitchell 1, Precision Tune, OTC, O'Reilly Auto Parts, BWD, JD Byrider, Snap-on Vetronix and Standard Ignition programs. You may have also seen Fulton in many Lightning Bolt Training videos and DVDs and read his articles in many auto service magazines. He currently owns and operates Ohio Automotive Technology, which is an automotive repair and research development center.

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