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John Rogers is a mobile tech in the Medford, NY area and writes about his work. In this post he uses his brand new PicoScope to view crankshaft and camshaft sensors on a 2004 Chrysler PT Cruiser which and now runs worse than before with code P2302 after an aftermarket PCM was installed.

I arrived at the shop started the vehicle and indeed it ran poorly with a substantial misfire. I pulled a code P2302 code. This code is for coil #1 Insufficient Ionization. This is a very common code on Chrysler vehicles. On this Chrysler style ignition system the ASD (Automatic Shutdown) relay supplies battery power to the positive side of the coil. The voltage flows through the primary windings of the coil out the coil negative terminal back to the PCM. The PCM is the ignition module and responsible for primary triggering. This code sets when it does not see proper primary events. The flowchart for this code is vague at best. I see many reasons for this code. But I always start with a Crankshaft Sensor and Camshaft Sensor scope test looking at the signals and the relationship. This is of particularly great importance on this vehicle. I see timing belt installation errors all the time. On this vehicle timing belt jobs can be challenging. Yes, you can look at cam and crank error in degrees with the scan tool. But, I want to see the raw data.

Is it a grounded circuit, a grounded PCM driver, a bad connection at the coil connector, an open primary circuit in the coil itself?

Read the complete story at JWR Automotive Diagnostics.