Comprehensive diagnostic guide for OBD-II code P1355 Ignition D Primary Circuit Fault

• do not contain an explicit, vehicle-wide definition of P1355. A related open-source entry lists translated as "Ignition D primary - defective circuit," which aligns with the general idea of a fault in the primary ignition circuit for ignition coil D. Use this as the best mapping available from the given sources, and treat P1355 as an ignition-coil primary-circuit fault associated with coil D (cylinder D) in configurations that number coils or pack elements D.
• For broader context, OBD-II diagnostic trouble codes are produced by the powertrain control module (PCM) and are intended to monitor various parameters; Powertrain Codes fall under the umbrella of DTCs that can trigger the Malfunction Indicator Lamp (MIL) when issues are detected.

1) Code overview and what P1355 generally means (based on sources)

• Where the sources provide a direct code mapping, P1355 is interpreted as an ignition-related fault in the primary circuit for the D ignition channel (ignition coil D). The exact OEM definition may vary by vehicle, but the open-source listing aligns P1355 with Because official OEM definitions aren't detailed , treat P1355 as a coil-driver/primary-circuit issue associated with ignition coil D and the related driver circuitry.
• In the OBD-II context, P1355 is a Powertrain code (in the "Powertrain Codes" group), meaning the PCM is detecting a fault in the ignition system (among other engine management subsystems).

2) Common symptoms you might see (informed by typical ignition-circuit faults)

• Check Engine Light (MIL) presence with P1355 stored or pending.
• Engine running rough, misfire-like symptoms on the cylinder associated with coil D (rough idle, hesitation, misfire feel under load).
• Loss of power or reduced acceleration capability, especially under heavy load or at steady speed.
• Increased fuel consumption or erratic idle behavior.
• In some cases, no noticeable drivability issue if the fault is intermittent or if fault is detected but not actively misfiring.
• Note: If multiple ignition-related faults co-exist (e.g., P0351-P0356 family codes) or there are misfire codes (P0301-P030X), this strengthens the likelihood of ignition-coil or driver/wiring problems. The general principle that DTCs monitor ignition parameters and trigger codes when issues are detected comes from the OBD-II overview.

3) Quick checks (safety and initial verification)

• Visual inspection: Inspect coil D and its wiring harness/connector for damaged insulation, corrosion, moisture, or bent/pinched wires. Look for damaged connectors on the coil pack or coil-on-plug module if applicable.
• Battery and charging system: Verify adequate voltage supply (proper battery voltage, healthy alternator output) since ignition circuitry is voltage-sensitive. A weak battery or poor ground can create intermittent ignition symptoms.
• Scan for related codes: Note any accompanying P035x codes (ignition coil primary/secondary faults for other cylinders) or P030x codes (cylinder misfire). This helps determine if the issue is isolated to coil D or systemic in the ignition system.

Why these checks are suggested: they align with general DTC monitoring concepts (Powertrain Codes monitor ignition parameters, and the ignition circuit faults commonly surface as coil/driver/wiring problems). Sources: Wikipedia - OBD-II (Diagnostic Trouble Codes); Wikipedia - OBD-II (Powertrain Codes).

4) Diagnostic flow (step-by-step)

Step 1: Confirm and contextualize

• Confirm P1355 is present with scan data. Check freeze-frame data and see if other ignition-related codes are present (especially P0351-P0356, P030x).
• Review engine load, rpm, and cylinder misfire history in the data to guide testing.

Step 2: Inspect the ignition coil D primary circuit components

• Inspect coil D, its secondary/primary wiring, and its connector for visible damage, corrosion, or moisture intrusion.
• If accessible, compare coil D primary circuit resistance (or coil D primary circuit function) against known-good values or against the other ignition coils in the same vehicle, per OEM service information. The sources provide a general emphasis on ignition circuits and coil-related faults but do not specify exact resistance values. Use manufacturer specs if available.

Step 3: Electrical tests (coil D circuit)

• Perform a resistance/continuity check on the coil D primary circuit wiring and connector from the PCM/driver side to the coil primary terminal(s). Look for opens, shorts to ground, or shorts to voltage.
• If equipped, use an oscilloscope or ignition scope to observe the coil D primary ignition signal (dwell/pulse width, waveform shape) during cranking and normal running. Inconsistent or missing drive signals point toward driver/PCM faults or wiring issues rather than a purely mechanical ignition fault.
• If coil D is a stand-alone coil or coil-on-plug, swapping coils (coil D with another coil position) can help isolate whether the fault follows the coil or stays with the cylinder/driver.

Step 4: Mechanical and ancillary checks

• Spark plug condition for cylinder D: inspect plug end, gap, and electrode wear; a faulty or fouled plug can contribute to misfire-like symptoms that resemble a coil issue. If the plug is suspect, service per OEM specs (replace as needed).
• Cylinder compression/engine mechanicals: while less common for an electrical fault, a compression issue can cause misfires and trigger ignition-related trouble codes. If electrical tests are inconclusive, consider a compression/ leak-down test on cylinder D.

Step 5: Evaluate PCM/driver functionality

• If the coil and wiring check out, and the coil's behavior changes only when swapped with another coil, the coil may be the fault. If the coil remains faulty in the new location, or if the coil still presents the same fault, suspect the ignition driver/PCM channel for coil D. The PCM's coil-driver transistor or related circuitry could be at fault, especially if multiple ignition circuits show symptoms in the same engine.
• In some cases, a PCM/driver fault is not easily diagnosed with basic tests and may require service information from OEM for diagnostic procedures, or a known-good replacement (or reflash/programmable update) per OEM guidelines.

Step 6: Re-check and road-test verification

• After replacement of coil D or the wiring/harness repair, clear codes and run the engine through a road test. Confirm no reappearance of P1355 and verify that misfire symptoms have resolved (if they were present).
• Confirm there are no remaining related codes and that fuel trims have returned to normal in the freeze-frame and live data.

5) Probable causes and estimated likelihoods (qualitative probabilities)

Note: The following probability ranges are informed by field experience and typical automotive fault patterns for ignition-primary-circuit problems. They are not derived from a published NHTSA statistic set , but reflect common trends seen in practice when dealing with ignition-coil primary circuit faults.

• Faulty ignition coil D primary circuit (coil D itself or coil-pack/coil-on-plug unit): 45-60%
  • Most ignition-related DTCs trace to a faulty coil or its primary driver. If coil D is defective or the coil's primary function is impaired, P1355 will typically be observed.
• Faulty ignition driver/PCM channel for coil D (driver transistor, wiring from PCM to coil, or PCM fault): 10-20%
  • If the coil and wiring look sound but the drive signal is inconsistent or absent, internal PCM driver or channel fault is a possibility.
• Wiring harness/connectors and harness integrity (open/short to ground, poor contact, corrosion): 15-25%
  • Poor electrical connections or damaged harness insulation around the coil D circuit are common contributors to intermittent or persistent P1355 faults.
• Spark plug condition or mechanical cylinder issues contributing to misfire (less likely sole cause of P1355 but can accompany it): 5-15%
  • While P1355 points to the primary ignition circuit, a worn plug or a related mechanical issue can produce symptoms that mimic a coil-driver problem. If P1355 is present with misfire codes or misfire symptoms, check plugs and compression as part of a complete diagnosis.
• PCM/ECU fault beyond the coil driver (rare but possible): 5-10%
  • In some cases, a PCM fault could manifest as ignition-primary-circuit faults; this is less common but worth considering if all other checks fail and OEM procedures indicate a PCM issue.

Caveat: These percentages are broad industry-field estimates. Vehicle make/model, coil architecture (coil-on-plug vs. coil packs), and the number of ignition channels can shift these probabilities significantly.

6) Testing and verification tools (relevant to this code)

• Scan tool with live data and freeze-frame: To confirm P1355 and view related data (engine RPM, load, misfire counters, and related ignition codes if present). The existence of P1355 is a Powertrain Code, and the general role of Powertrain Codes is documented in the Wikipedia OBD-II overview.
• Oscilloscope or ignition scope (preferred): To observe coil primary current waveform, dwell and ignition signal timing for coil D.
• Multimeter with capability to measure coil primary resistance (if accessible) and continuity checks on wiring and connectors.
• OEM service information (factory manual) for coil primary resistance specs and wiring diagram usage.

7) Safety considerations

• IGNITION systems and coil packs are part of high-voltage circuits; de-energize the system properly before disconnecting connectors. Follow standard shop safety procedures (disconnect battery, discharge capacitors, wear eye protection, etc.).
• When performing spark plug, coil, or wiring work near fuel and air intake paths or hot engine components, use caution to prevent ignition of flammable vapors.

8) Repair options (typical remedies)

• If coil D or coil-pack/coil-on-plug is faulty: replace coil D and re-test; use OEM-specific replacement parts per vehicle.
• If wiring harness/connector is damaged: repair or replace the harness segment, clean or reseat connectors, and ensure secure, corrosion-free connections.
• If coil D driver/PCM channel is suspected: rely on OEM guidance; the PCM may require reprogramming, a dealer diagnostic procedure, or replacement if proven defective.
• If spark plug or cylinder mechanical issues are found: replace plugs as necessary; perform compression test if indicated by testing results.
• After repair, clear codes and perform road test to verify that P1355 does not reappear and that engine performance has returned to normal.

9) Road-test and verification checklist

• Start engine and monitor P1355 status; ensure MIL stays off after repair.
• Drive through varying loads and speeds to confirm resolution of symptoms (misfire, rough idle, power loss).
• Re-check for additional codes (P035x, P030x, etc.) that may indicate remaining issues.
• Confirm fuel trims and ignition timing behavior look normal in live data.

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.

---