I recently purchased a 2001 Ford Expedition with a P0353 diagnostic trouble code. I've already replaced both the ignition coil and spark plugs, and confirmed that power is present in the wires leading to the coil. Despite these steps, the code persists. What should be my next troubleshooting step? Is it possible the issue lies in the wiring harness, the ignition module, or another component?
The P0353 code points to a failure in the ignition coil C's primary or secondary circuit. Does this mean the crankshaft position sensor is faulty? No—this code relates directly to the ignition system, not engine speed sensing.
The 2001 Ford Expedition uses a Coil-On-Plug (COP) system where each spark plug has its own dedicated ignition coil. Is this configuration correct? What brand of ignition coil did you install? How are you testing the wires—using a digital multimeter (DVM) or a test light? Where is the grounding point located, and what is the location of the ignition module—internal to the Powertrain Control Module (PCM) or external like in older Ford models?
The coil I used is a standard COP unit from AutoZone. I tested it with a test light and believe the ignition module is controlled internally by the PCM.
So this vehicle uses a Coil-On-Plug (COP) system? Did you experience a misfire before replacing the coils and plugs? If I remove the new coil from cylinder 3 and install it in another cylinder on the opposite bank, does the P0353 code change?
Yes, prior to the replacement, I noticed a misfire specifically in cylinders 3 and 4. After replacing both plugs and coils, the issue appears to be isolated to cylinder 3.
If you take the new AutoZone coil from cylinder 3 and install it into another cylinder on the opposite bank—does the P0353 code change? This test can help determine if the issue is with the coil or its wiring.
No—the code remains P0353 even when moved to a different cylinder.
That suggests there may be an open circuit or high resistance in the wiring leading to the coil, resulting in insufficient spark. The ignition system is not generating proper voltage at that cylinder.
Could this indicate a faulty PCM sending incorrect signals to the coil? Is it possible the timing or signal output from the computer is off?
While that's a possibility, it's less likely. Ignition coils and wiring are more common failure points in this model. Before concluding the PCM is faulty—especially given its relatively low failure rate on Fords—it’s important to rule out other components such as wiring integrity, ground connections, or coil installation issues.
I’ve confirmed that the wire from the PCM shows good continuity. Power is present at the coil terminal, and I even tested with a used PCM—same result. The same coil works perfectly when installed in another cylinder. This makes me increasingly confused about the root cause.
Can you clarify how the wire test was performed? Does it show full continuity, 12 volts at the terminal, and a proper ground connection? A low resistance reading (under 0.5 ohms) is not sufficient to verify ignition driver function. I’ve seen many wires pass these tests yet fail under actual load when energized—no spark despite apparent voltage.
P0353 is not a crankshaft position sensor code—it's specifically for an ignition coil primary/secondary circuit malfunction. This indicates a problem with the spark generation system, not engine timing.