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Dan, Technician
Category: Mercury
Satisfied Customers: 24468
Experience:  Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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lincoln ls 2005 3.0 dtc code p0355 - primary/secondary coil

Resolved Question:

lincoln ls 2005 3.0
dtc code: p0355 - primary/secondary coil "e" malfunction - replaced all plugs and coils #4 & #5 - initially sliht misfires but gradually getting worse - checked injectors and cleaned - dtc code reappears - short term fuel trim #3/long term fuel trim #3 and short & long term fuel trim #4 pid reads -100.6% - is pcm the culprit or primary wiring possible?
Submitted: 7 years ago.
Category: Mercury
Expert:  Dan replied 7 years ago.

If that is the code your getting and you replaced the #5 coil the problem is either the wiring or the pcm. You can swap a coil with another cylinder just to make sure you did not get a defective coil and the next step is to check for shorts, connector conditions, or high resistance in the wiring. Here is a wire diagram, let me know if you have questions. Thanks


P0355 Ignition COP 5 Primary/Secondary Circuit Malfunction - With Automatic Transmission

Possible CausesSetting Conditions
  • Ignition START/RUN circuit is open or shorted to ground
  • Ignition COP connector is damaged (check pins for damage, and for moisture)
  • Ignition COP driver control circuit open, shorted to ground or shorted to voltage
  • Ignition COP has failed
  • PCM has failed

Customer: replied 7 years ago.

wouldn't the igniton start/run switch affect the power supply to all the coils in lieu of just one?


I replaced the cop with a new one two times with the same result and the connector appears clean and straight prongs


would the pcm affect just one coil and I assume a new pcm would require to have the parameters installed by Lincoln

Expert:  Dan replied 7 years ago.
Ya it would but that is kinda generic reading so that would not apply. You basically just need to make sure you have good power on that coil then check resistance and for shorts on the control wire. The PCM could just effect on coil and your correct it would need to be programmed by lincoln. Let me know if you have more questions, thanks.
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