A Ford P0355 code is an error code that signals a primary control circuit malfunction in an ignition coil. This code can be triggered by multiple causes, such as an open or shorted VPWR circuit, or a damaged COP. When this code is set, the PCM enters Failure Mode Effects Management (FMEM), which shuts down the injector for the associated cylinder in order to protect the catalytic converter. Diagnosing and resolving this code can be difficult, and should not be attempted without first using a 12-volt non-powered test lamp to verify VPWR voltage at the ignition coil harness connector. To help with this process, Ford has released two service bulletins that provide further information and solutions for P0355 code issues. Any Ford driver can identify and correct this issue with the proper knowledge and tools.
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Causes and Solutions for Ford P0355 Code
| Cause | Solution |
|---|---|
| VPWR circuit open | Verify VPWR voltage at the ignition coil harness connector with a 12-volt non-powered test lamp. |
| VPWR circuit short to ground | Check the coil driver circuit for open, short to voltage, or short to ground. |
| COP5 circuit open | Look for signs of damage or corrosion in the COP5 circuit. |
| Damaged COP | Replace the COP with a new one, if necessary. |
Open VPWR Circuit
When the VPWR circuit is open, the Powertrain Control Module (PCM) can no longer detect the voltage coming from the ignition coil. To verify this issue, a 12-volt non-powered test lamp should be used to measure the voltage at the ignition coil harness connector. If the voltage is not detected, then it is likely that the VPWR circuit is open.
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Short to Ground VPWR Circuit
If the VPWR circuit is short to ground, then the PCM will be unable to detect the voltage coming from the ignition coil. The coil driver circuit should be checked for an open, short to voltage, or short to ground to diagnose this issue. If any of these issues are found, they must be corrected before proceeding.
Open COP5 Circuit
When the COP5 circuit is open, the PCM is unable to detect the voltage coming from the ignition coil. To verify this issue, look for signs of damage or corrosion in the COP5 circuit. If any damage or corrosion is found, then it must be corrected before proceeding.
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Damaged COP
If the COP is damaged, then the PCM will be unable to detect the voltage coming from the ignition coil. To diagnose this issue, the COP should be replaced with a new one, if necessary.
Conclusion
Ford P0355 code is an error code that signals a primary control circuit malfunction in an ignition coil. This code can be triggered by multiple causes, such as an open or shorted VPWR circuit, or a damaged COP. To diagnose and resolve this code, Ford has released two service bulletins that provide further information and solutions. With the proper knowledge and tools, any Ford driver can identify and correct the Ford P0355 Code issue.
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