P1413 -- Secondary Air Injection System Supervisor - Low Input Signal

P1413 - Secondary Air Injection System Supervisor - Low Input Signal

Overview

• Code interpretation (based on available open-source definition): P1413 corresponds to a fault in the Secondary Air Injection (SAI) system where the SAI supervisor (control/monitoring circuit) reports a low input signal. In other words, the ECM/PCM is receiving or interpreting an input from the SAI supervisor as unexpectedly low.
  • Source note: This definition appears in an Open Source repository listing "Secundária Supervisor injeção de ar - sinal de entrada baixo" (Portuguese for "Secondary Air Injection Supervisor - Low Input Signal"). This aligns with the P1413 categorization for SAI-related supervision signals.

• Category: P1413 is a powertrain/Emissions-related diagnostic code (OBD-II) and sits within the broader Powertrain Codes family described in the OBD-II context.

Important Notes

• The available sources do not provide a vehicle-agnostic official OEM definition for P1413 beyond the open-source entry. The guide uses the open-source translation/definition as the working definition and frames it within the OBD-II powertrain/emissions context per Wikipedia's OBD-II overview.

Symptoms

• MIL (Check Engine Light) illumination with code P1413 stored in the PCM.
• Emissions readiness test may fail or have trouble passing an inspection due to an SAI supervision fault.
• Possible driving report (to the extent the consumer notes it): engine may run normally when the light is on, or there may be intermittent roughness/poor idle only if the SAI impact affects intake/exhaust balance, though P1413 primarily signals an electrical/ supervisor input issue rather than a direct drivability fault.
  • Note: Symptoms listed here reflect typical user-reported behavior for SAI supervision issues in the broader OBD-II context and are not a law or guarantee of performance. They are included to help you recognize what a customer might report.

Likely root causes (probability guidance)
Because P1413 is defined as a low input signal to the SAI supervisor, the most common root causes tend to involve wiring, wiring integrity, power/ground references, and the SAI hardware/supervisor signal path. and patterns seen in similar SAI-related codes, the following ranked possibilities are reasonable (probabilities are approximate and vehicle-specific):

• Wiring/connector issues to the SAI supervisor input, sensor, or related control circuit (loose connector, corrosion, frayed harness) - ~40-50%
• Faulty or degraded SAI fuse/relay or power supply to the SAI system (blown fuse, failed relay,Battery/ECT related supply issue) - ~5-10%
• Faulty SAI sensor, supervisor input sensor, or interface component producing a genuinely low signal (sensor failure or degraded signal integrity) - ~5-15%
• Faulty SAI pump, diverter/check valve, or related actuator affecting the signal path (mechanical fault causing abnormal readings or supervision loss) - ~5-15%
• PCM/ECU software or calibration issue affecting how the SAI supervisor signal is interpreted - ~0-10%
• Other related SAI hardware issues or service bulletin requirements (rare but possible) - ~0-5%
• If there are OEM-specific service bulletins, they may supersede these general estimates.

Note on data sources

• NHTSA complaint frequency data is not provided in the given sources for P1413, so probability figures here rely on ASE field experience and common SAI-related code patterns. for P1413 in your vehicle/application, update these estimates accordingly.

Diagnostic Approach

Tools Needed

• OBD-II scan tool (with freeze-frame data and live data capability)
• DVOM/multi-meter (for voltage and ground checks)
• Wiring diagrams for the SAI system (vehicle-specific)
• Basic hand tools, power supply test leads, and a safe workspace
• If applicable: SAI pump/valve diagnostics, service bulletins

1) Verify the code and collect baseline data

• Confirm P1413 is present with a current fault code. Note freeze-frame data, engine RPM, engine load, coolant temp, indicated fault mode, and any related stored codes (e.g., P0410-P0413 family).
• Check for any active vs. pending codes and the status of readiness monitors. DTCs are part of the emissions/monitoring framework, so verify the readiness state after repairs.

2) Check for related or companion codes

• Look for other SAI-related codes (P0410-P0413) which may point to specific components (pump, relay, diverter valve) or signaling issues.
• If no related codes exist, still proceed to electrical and signal path checks, as P1413 is specifically about the input signal.

3) Perform a thorough visual inspection

• Inspect all visible wiring harnesses and connectors to the SAI supervisor, pump, and control valves. Look for damaged insulation, pin corrosion, bent pins, or loose connectors.
• Inspect fuses and relays associated with the SAI system. A blown fuse or faulty relay is a common cause of an "input signal low" condition due to loss of supply or reference signal.
• Inspect the SAI air pump, diverter valve or check valve, and associated vacuum/plumbing for leaks or blockages that could affect system operation or the supervisory signal indirectly.
• Document any signs of aftermarket wiring modifications or previous repairs that might have introduced a fault.

4) Electrical path testing (signal and power)

• With key to ON (engine off), verify the SAI supervisor input circuit has the expected power supply and reference ground. Use the vehicle's service manual or wiring diagram to locate the correct pins.
• Check for proper battery voltage on the SAI supply, and verify clean, solid ground at the supervisor and related components.
• Perform a resistance check on relevant circuit wires if a reasonable spec is available from the service data. Look for open circuit, high resistance, or short to ground.
• If the input signal is clearly low, compare measured values against spec. A voltage that is abnormally low relative to the expected reference would support a fault in the sensor, wiring, or supply path rather than a purely mechanical issue.

5) Functional/system operation testing

• If accessible, check if the SAI pump runs during the appropriate engine conditions (cold start, or when the SAI control logic requires it) and listen for operation. A non-running pump in expected cycles may indicate a circuit or pump fault.
• Confirm the SAI diverter valve or check valve operation if equipped. A stuck valve or leak can produce abnormal readings and affect the supervisor's signal depending on the system design.
• Review any OEM service bulletins for P1413 or SAI-related issues specific to the vehicle; some platforms require updates, reprogramming, or component replacements as part of a bulletin.

6) Scan for live data and interpret

• Use your scan tool to monitor relevant live data: SAI supervisor input signal, pump status, valve positions, and any related sensor data. Look for a consistently low input reading, a signal that toggles abnormally, or no signal at all.
• Correlate live data with engine state (cold/hot, RPM, load) to determine if the fault is intermittent or persistent.

7) Diagnose and repair plan

• If a wiring/connector issue is found: repair or replace the damaged harness/connector, clean grounds, re-seat connectors, and verify continuity.
• If a fuse/relay is defective: replace fuse/relay and confirm power/ground paths after replacement.
• If the SAI pump or valve is faulty: repair/replace the pump, valve, or associated actuator as appropriate; ensure mechanical movement and absence of leaks.
• If the supervisor input sensor/module is faulty: replace the sensor or the SAI supervisor module as recommended by OEM data; recheck signal integrity and monitor for code return after replacement.
• If an OEM service bulletin exists: follow the bulletin instructions (software updates, calibration procedures, recommended parts, etc.).
• After any repair, clear DTCs, perform a drive cycle, and re-scan to verify the fault does not return and the readiness monitors transition to ready.

8) Drive cycle and confirmation

• Drive the vehicle under normal operating conditions to verify that the P1413 code does not return and that the SAI-related monitors progress to "ready" if applicable. Emissions readiness considerations per OBD-II guidelines apply here.

documentation and reporting

• Document all findings, wiring paths checked, test results (voltage/gnd readings, continuity), parts replaced, and service bulletins consulted.
• Record final status: code cleared, ready/complete status, and any recommended follow-up if the fault reappears.

Safety Considerations

• Disconnect battery prior to wiring repairs where required.
• Exercise caution around air injection components (pump can spin unexpectedly when power is applied).
• Ensure proper PPE and avoid inhalation of any fumes; follow all shop safety protocols when working around emissions-related systems.
• Use proper OEM service information to avoid misdiagnosis and incorrect repairs, especially when dealing with emission-related systems.

Summary table (quick reference)

• Code: P1413 - Secondary Air Injection System Supervisor - Low Input Signal

• Primary cause category: Electrical/signal integrity in SAI supervision path (wiring/ground/fuse/relay, sensor, or controller)

• Common symptoms: MIL on; possible emissions readiness issues; no direct drivability impact in many cases

• Key diagnostic steps: Confirm code, inspect wiring/connectors, test power/ground, verify SAI pump/valves operation, review service bulletins, clear codes and re-test

• Probable fixes (order of operation): Repair wiring/ground/fuses, replace failed relay or pump/valve, replace faulty sensor or supervisor module, apply OEM updates if required

• Expected data to collect: Live SAI input signal, pump/valve status, fuse/relay status, continuity and resistance measurements

• Wikipedia - OBD-II: Diagnostic Trouble Codes (context for how DTCs function in OBD-II systems; general framework for powertrain codes) and OBD-II Powertrain Codes (categorization and scope). These provide foundational context for DTC structure and emissions-related monitoring.

• Open Source code entry - Secundária Supervisor injeção de ar - sinal de entrada baixo (Secondary Air Injection Supervisor - Low Input Signal). This entry provides a direct interpretation of P1413 as a signal-level fault in the SAI supervision path and is used here as the working definition for this guide.

• Emissions and diagnostics context - OBD-II Emissions Testing section provides context about how DTCs tie into emissions readiness and testing, which is useful when addressing potential inspection-related impacts of P1413.

Notes on conflicts

• The P1413 definition is not universally published in a single official OEM-agnostic source within the provided material. The guide uses the open-source definition for P1413 and aligns it with the general OBD-II and emissions context from Wikipedia. If OEM-specific documentation is available, prefer that definition and adjust the diagnostic flow accordingly.
• If you encounter conflicting descriptions in a vehicle-specific shop manual, prioritize the OEM's diagnostic tree and wiring diagrams for P1413 and treat the open-source definition as a supplemental reference.

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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