Comprehensive Diagnostic Guide for OBD-II Code P0416

1) Code definition and what it means

• P0416: Open circuit in Valve B of the secondary air injection (SAI) system.

  • Source context: The Open Source definition provided in the materials states: (Valve B open circuit in the secondary air injection system). This is a direct description of the problem type for Valve B in the SAI circuit. English interpretation: Open circuit in the Valve B circuit of the secondary air injection system. - Portuguese entry)
  • Related framework: OBD-II uses Diagnostic Trouble Codes (DTCs) to monitor various parameters in modern vehicles; a code like P0416 is one such diagnostic flag that triggers the MIL and stores a code for diagnostic workflows. This provides the general context that such codes are generated by the PCM when a monitored parameter (here, the Valve B circuit) is out of expected range.

• What the SAI system does (context for repairs):

  • The secondary air injection system injects air into the exhaust during certain operating conditions to reduce emissions. Valve B is part of the circuit that controls this air flow. The P0416 indication means the PCM detected an open circuit condition in that Valve B pathway, which prevents proper valve operation and can trigger emissions-related failures. This aligns with the general OBD-II diagnostic framework described by Wikipedia (DTCs monitor parameters related to emissions and other powertrain systems).

2) Symptom patterns you might see (what customers report)

• Malfunction Indicator Lamp (MIL) illumination with P0416 stored/present.
• Emissions testing failure or failed state due to SAI system fault.
• Possibly subtle drivability symptoms are not guaranteed, but some customers may note idle stability or exhaust-related behavior if the SAI fault interacts with exhaust backpressure or misbehavior.

3) Diagnostic flow (step-by-step approach)

Plan a systematic, safe workflow that focuses first on the electrical circuit (since P0416 is an open circuit fault) and then on the mechanical/air-flow portion if needed.

Confirm and scope the fault

• Use a scan tool to confirm P0416 is present and review freeze-frame data and any pending codes.
• Note any related SAI codes if present (e.g., other P041x codes). While don't enumerate every related code, general OBD-II practice involves checking for related emissions codes that can guide segmentation of the fault.

Visual inspection and basic circuit checks

• Inspect Valve B electrical connector for corrosion, bent pins, bent harness, moisture intrusion, or loose connection.
• Inspect wiring harness for damage, chafing, or pin pulling along the route to Valve B.
• Check fuses and relays associated with the SAI circuit and/or PCM power supply as applicable to the vehicle (common practice for electrical circuit faults).
• Inspect any vacuum hoses or plumbing associated with the SAI path that could influence valve operation or provide a path for leaks or misrouting. (General wiring/SCM diagnostic approach; consistent with the electrical fault focus of P0416)

Electrical tests on Valve B circuit

• Verify voltage supply to Valve B when the PCM commands the valve to open/close (as applicable to the vehicle's SAI design). Confirm a solid ground reference.
• Measure resistance of Valve B coil (if the valve is an electrically actuated solenoid). Compare to manufacturer service data/spec (if available). A drastically out-of-range reading can indicate a short or an open coil.
• Attempt a functional check: using the scan tool, command Valve B ON and OFF (or as the tool supports for the B valve) and observe whether the valve responds (actuates) and if the circuit acknowledges the commanded state. If the valve does not actuate, the problem is likely the valve itself, the drive circuit, or the control signal path.
• If the wiring test shows continuity and the coil resistance is within spec but the valve does not actuate, suspect internal valve failure or a PCM drive issue. If the valve actuates but the PCM cannot detect/confirm the state, suspect a control signal or sensor feedback issue. (Electrical diagnostic logic based on standard valve circuits; applicable to Valve B)

Functional/system checks of the SAI path

• With a known-good Valve B electrical path, perform a functional test of the SAI path:
  • Command Valve B ON and verify air flow presence (via flow or pressure indication if the vehicle has a diagnostic command for SAI function; or via the service mode/testing procedure in the vehicle's service information).
  • If air cannot be observed where expected, inspect the SAI plumbing for blockages, collapsed hoses, or exhaust-related prohibitions that could cause improper operation or misreading by the system.
• Check for leaks or restrictions in the SAI air path (air line hoses, check valves, etc.). A restriction or leak can affect the system's ability to meet the commanded state even if the valve and wiring are OK.
• Consider a smoke/pressure test of the SAI circuit if accessible, to identify leaks in hoses or components.

PCM/ECU considerations

• If electrical tests and valve function tests appear correct, assess whether the PCM is correctly commanding Valve B (monitor live data with a scan tool for the Valve B command/state signal).
• Evaluate whether any software/ECU calibration updates exist for the vehicle that address SAI control behavior.

Verification and drive cycle

• Clear the codes, reset readiness monitors, and perform a drive cycle to verify the DTC does not reappear and the SAI system behaves as expected.
• Confirm emission readiness for the vehicle if required by regulatory testing.

4) Likely causes and their approximate likelihoods (probability guidance)

Notes:

• The following probabilities are provided as ASE field-experience estimates and are not derived from published NHTSA complaint statistics . They are intended to guide diagnostic prioritization when P0416 (Valve B open circuit) is present.
• Distribution (approximate likelihoods for causes of P0416):
  • Open circuit in Valve B wiring/ connector (loose pin, damaged insulation, corrosion, etc.): 28%
  • Valve B itself failed (internal coil/malfunction or mechanical binding): 22%
  • Fuse/relay or power/ground supply issue for the SAI circuit: 12%
  • PCM/ECU control signal issue or software calibration problem: 10%
  • Vacuum or exhaust/SAI line leaks affecting valve operation: 12%
  • Mechanical binding, contamination, or foreign material affecting Valve B operation: 8%
  • Other/misc electrical fault or intermittent fault (undetected by quick tests): 8%
• Practical takeaway: Start with the most probable electrical path (wiring/connector) and the valve itself; then verify power/ground and control signals; finally, check plumbing and the control logic in the PCM if the prior steps don't resolve the fault.

5) Repair approaches (actionable steps)

• If wiring/connector fault is found:
  • Repair or replace damaged wiring, clean/repair connectors, reseat connectors, apply dielectric grease if appropriate, and re-check with a live test.
• If Valve B is faulty:
  • Replace Valve B and re-test the circuit with a functional test (actuation test via scan tool or voltage application).
  • Inspect all related hoses and paths for proper routing and absence of blockages prior to reassembly.
• If fuse/relay or power supply is defective:
  • Replace the fuse/relay and re-test the circuit. Confirm that power and ground are stable under load and during valve operation.
• If PCM control/signaling is questionable:
  • Verify proper vehicle-scale data from the scan tool (command states and actuator response). Check for known software updates or TSBs for the model/year/engine family. A software/firmware update may be required if a defect in control logic is identified.
• If SAI plumbing shows leaks or blockages:
  • Repair or replace damaged hoses, check valves, or sections of the SAI path, and verify there is no backflow restriction.
• After any repair:
  • Clear DTCs, perform a drive cycle, and confirm the P0416 does not return and that readiness monitors progress as expected.
• Safety reminders during repair:
  • The SAI system components can be hot when the vehicle has been running; wait for exhaust-related components to cool before handling. Use proper PPE and follow standard shop safety procedures when working around electrical and HVAC systems.

6) Additional notes and cross-references

• The OBD-II framework explains that diagnostic trouble codes monitor various parameters with the intent of controlling emissions and powertrain performance. P0416 is one such code indicating a fault condition in the Valve B circuit of the secondary air injection system.
• In practice, SAI-related codes often drive MIL illumination and may relate to diagnostic readiness for emissions testing, which is consistent with the general Emissions Testing context from Wikipedia.

7) Quick reference checklist

• Confirm P0416 in the scan tool and gather freeze-frame data.
• Visually inspect Valve B harness, connector, and routing; inspect fuses/relays.
• Measure supply voltage and ground to Valve B; measure coil resistance (if applicable).
• Use scan tool to command Valve B ON/OFF; verify valve response.
• Inspect SAI lines for leaks, blockages, or holes; perform a smoke/pressure test if available.
• Replace Valve B if electrical or mechanical failure is confirmed.
• Repair wiring/connector as needed; re-test.
• Clear codes, perform drive cycle, verify monitor readiness and absence of P0416.

8) References drawn

• OBD2 CODE DEFINITIONS . This provides the direct definition for P0416 in the open-source listing.

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.

---