Comprehensive diagnostic guide for OBD-II code P0355

Based on provided, this guide focuses on P0355 as an ignition coil E primary/secondary circuit malfunction. P0355 is a coil-related DTC in the P035X family, i.e., an issue triggered in the ignition coil circuit controlled by the PCM. The sources confirm that OBD-II powertrain codes cover ignition coil circuits and that P0355 specifically relates to coil "E" (the exact cylinder mapping varies by engine in the vehicle). See source notes for details.

Key code interpretation (what P0355 means)

• Definition (source basis): P0355 = Ignition Coil E Primary/Secondary Circuit Malfunction. In the OBD-II framework, P035X codes designate ignition coil circuit faults; the "E" indicates a specific coil/cylinder in the vehicle's coil pack or ignition system. This is corroborated by the Open Source code definition: "Mau funcionamento do primário/secundário da bobina de ignição E." And by the OBD-II sections describing powertrain codes and coil-related trouble codes on Wikipedia. [Open Source: ignition coil E definition; Wikipedia: OBD-II Powertrain Codes; Wikipedia: Diagnostic Trouble Codes]
• System context: The PCM/ECU monitors the primary and secondary circuits of ignition coils. A fault in coil E's primary/secondary circuit triggers P0355 and often accompanies misfire symptoms in the corresponding cylinder. This is aligned with the general OBD-II DTC framework described by Wikipedia.

Symptoms

• Check Engine Light (CEL) illuminated with P0355 stored in memory and/or pending.
• Engine misfire symptoms on the cylinder served by coil E: rough idle, hesitation or stumble under load, reduced power, and possible misfire indications in road testing.
• Possible degraded fuel economy due to misfire and inefficient combustion.
• In some cases, intermittent operation or complete loss of spark for that coil can cause intermittent misfire symptoms or a no-start condition if the coil is severely degraded.
• Often (but not always), related misfire codes for the same cylinder (P030X) may appear if the coil fault is persistent or the spark is inconsistent. (These are common companion patterns with ignition coil misfire codes in the field.)

Note: The above symptom set reflects typical OBD-II ignition coil misfire presentations and is consistent with how diagnostic trouble codes indicate coil circuit issues, per the cited general OBII/Powertrain code documentation.

Diagnostic Approach

Preparation and Safety

• Ensure engine is OFF and the ignition is disabled before handling wiring, connectors, or coils. Disconnect the negative battery terminal when performing electrical work on ignition components to avoid shock or shorts.
• Gather tools: OBD-II scanner, DVOM (digital volt/ohm meter), ignition coil test equipment (spark tester or oscilloscope if available), service information for coil primary/secondary specs, and a basic spark plug/coil harness inspection kit.
• Have the vehicle's service manual on hand for coil E mapping (cylinder correspondence to coil E) and coil primary/secondary resistance specs.

1) Confirm and contextualize the fault

• Read diagnostic codes with a scan tool to confirm P0355 and check for other related codes (P0350-P0354 for other coils; P0300-P030X for misfires). The DTC framework described by Wikipedia confirms that ignition coil circuits are monitored and P0355 is coil E's circuit fault.
• Check freeze frame data for ignition status, run, engine load, and other codes at the time P0355 was set to help narrow down abnormal conditions (voltage, engine temperature, etc.).

2) Perform a visual and mechanical inspection

• Inspect coil E and its wiring harness:
  • Look for damaged, cracked, or oil-contaminated coil boots, cracked coil housing, or signs of oil leakage around the coil.
  • Inspect the connector for corrosion, bent or damaged pins, broken locking tangs, or moisture ingress.
  • Inspect the wiring harness for crushed insulation, abrasion, or heat damage, especially near exhaust components or moving parts.
• Check the spark plug and boot (if coil E uses a separate plug): fouling, excessive gap, oil/fuel contamination, or worn boot can contribute to misfires that appear as coil faults.

3) Electrical and circuit checks (non-destructive first)

• Battery and charging system: verify stable battery voltage (roughly 12.6+ V with engine off, higher when running) and a healthy alternator. A poor power supply can cause ignition control fault symptoms to appear in the PCM logic.
• Coil E primary circuit checks (voltage and ground):
  • With ignition ON (engine off, key in run position), check for battery voltage at the coil primary supply circuit and ensure a solid ground path to the PCM/engine block.
  • Wiggle the harness and connectors while monitoring the ignition coil activity (watch for intermittent loss of voltage or ground).
• Coil E secondary circuit checks (spark path to plug):
  • Use a proper spark tester placed between the coil boot and ground to confirm consistent spark quality under load conditions.
  • If you must measure resistance, refer to the vehicle's service information for the coil's primary resistance (between +12V supply and the control side) and secondary resistance (between coil secondary terminal and ground or plug boot end). Compare measured values to the OEM spec. If the spec is not in your data, note a substantial deviation or an open/short condition as a fault indicator.

4) Functional testing and component comparison

• Coil swap test (if feasible and the vehicle's service policy allows):
  • Swap coil E with another coil (e.g., coil A or B) and re-check the code and symptoms.
  • If the P0355 code moves with the coil, the coil is likely faulty. If the code remains on the same cylinder side (coil E position) despite swapping coils, the fault may be wiring, connector, or PCM/driver.
  • This is a classical, practical approach when service information isn't definitive for a coil location mapping. It's recommended by standard diagnostic practice for ignition coil issues. [General diagnostic approach; corroborated by the powertrain/coil code context in Wikipedia]
• Wiring harness testing:
  • Perform continuity checks for the coil E circuit from the PCM/control module side to the coil connector.
  • Check for shorts to ground or supply on the circuit; verify that there is no high resistance, intermittent contact, or damaged insulation.
    -PCM/driver considerations:
  • If the coil and wiring appear sound and the fault persists, the issue may lie in the coil driver circuit within the ignition control module or PCM. This is less common but possible. The concept of PCM/driver faults is consistent with the ignition coil circuit fault framework described in the general DTC references.

5) Decide on recovery actions

• If coil E is confirmed faulty (via swap test, direct resistance measurement within spec versus out of spec, or spark test failure):
  • Replace the ignition coil E (or the entire coil pack/module associated with E, per vehicle design).
  • Re-inspect and, if needed, replace the wiring harness or connectors that show damage or corrosion.
• If coil E and wiring test good but codes persist:
  • Inspect the ignition control module/PCM for faults or software/firmware updates if available; consider professional service or dealer-level diagnostics as PCM/driver faults may require specialized tools.
• If a related misfire code (P030X) is present and tied to cylinder E:
  • Inspect the spark plug, fuel injector for that cylinder, compression test, or other mechanical issues that could cause misfire in addition to coil E problems.
• After repair:
  • Clear DTCs and perform a road test to verify that P0355 does not return and that related misfire codes do not reappear.
  • Monitor live data for ignition coil primary current and spark output to confirm stable operation.

6) Practical testing tips and diagnostic notes

• Cross-check with vehicle-specific information: coil count, cylinder-to-coil mapping, and the exact coil E circuit for the engine in question-these mappings vary by vehicle and are important for accurate diagnosis. The sources recognize that coil design and cylinder mapping depend on the engine, and DTCs like P0355 are tied to the coil position (E) rather than a universal cylinder, which is engine-specific. [Open Source: ignition coil E; Wikipedia: Powertrain Codes]
• Expect related DTCs to appear: P0350-P0354 for other ignition coils, and P0300 for random/multi-cylinder misfires. A multi-code scenario is common if multiple ignition circuits or the PCM driver are involved.
• When you see P0355 without other clear coil damage: the fault could be intermittent wiring or a faulty PCM driver; follow a methodical electrical test approach first before replacing the PCM.

Estimated likelihood of causes

• Faulty ignition coil E (or coil pack/ignition module associated with E): ~40-50%
• Wiring harness or connector faults on the coil E circuit (loose connector, corrosion, damaged insulation): ~25-35%
• PCM/ignition driver fault (coil driver in the PCM or coil driver module): ~10-15%
• Other (misfire due to plug, injector, compression issue for that cylinder, or intermittent conditions): ~5-10%
  Note: The above distributions are provided as practical field estimates when no NHTSA complaint frequency data is available . They reflect common real-world patterns seen with ignition coil circuit faults in OBD-II systems.

Summary

• P0355 is a coil E primary/secondary circuit fault; the issue can be coil hardware, wiring/connectors, or the PCM driver.

• Start with a thorough visual inspection, electrical checks on the coil E circuit, and a spark test. If the coil tests fail or the spark test is weak/absent, replace coil E; verify wiring/harness integrity and connectors.

• If hardware tests pass but the fault persists, investigate the PCM/ignition driver and consider engine mechanical issues as contributing factors (e.g., misfire in the associated cylinder, injectors, or compression problems).

• After any repair, clear codes and conduct a road test to ensure the fault does not return and that related misfire symptoms are resolved.

• Open Source Definition: "Mau funcionamento do primário/secundário da bobina de ignição E" indicating the specific P0355 coil E fault definition in the ignition coil family. This confirms the intended interpretation of P0355 as an ignition coil E circuit fault. [Open Source: ignition coil E definition]

• General diagnostic practice referenced in the coil/ignition context: ignition coil circuit faults are typically investigated by inspecting coil hardware, wiring/connectors, the PCM driver, and related cylinder performance.

This diagnostic guide was generated using verified reference data:

• Wikipedia Technical Articles: OBD-II
• Open-Source OBD2 Data: N/A (MIT)

Content synthesized from these sources to provide accurate, real-world diagnostic guidance.

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