SFI SYSTEM, Diagnostic DTC:P0412

DTC Code DTC Name
P0412 Secondary Air Injection System Switching Valve "A" Circuit

DESCRIPTION

The secondary Air Injection (AI) system consists of an air pump, Air Switching Valve (ASV), Air Injection Control Driver (AID) and the ECM. When a cold engine is started, the AI system immediately pumps the secondary air to the exhaust port of the cylinder head to purify the exhaust emissions.

The ECM transmits command signals to the AID to drive the ASV and air pump. Then the AID drives them.

The AID has a function for pump and valve driving, and also has a diagnosis function for detecting malfunctions in the AI system circuit.

Tech Tips

The AID supplies the large amount of current required to drive the air pump and ASV.

A01E09FE03
DTC No. DTC Detection Condition Trouble Area
P0412

After cold engine starts, all of following conditions are met (1 trip detection logic):

(a) AI system not operating (air pump OFF and ASV OFF)

(b) Diagnostic signal from AID is 40%

(c) Battery voltage is 8 V or more

  • Open in air switching valve drive circuit

  • Short between ASV circuit and +B circuit

  • AID

  • ASV

  • ECM
P0412

After cold engine starts, all of following conditions are met:

(a) AI system not operating (air pump ON and ASV ON)

(b) Diagnostic signal from AID is 40%

(c) Battery voltage is 8 V or more

  • Short between ASV circuit and body ground

  • AID

  • ASV

  • ECM

MONITOR DESCRIPTION

Air Injection Control Driver (AID) detects an open or short in the air pump and ASV circuit according to the terminal voltage and sends a signal as the diagnostic information to the ECM.

When a cold engine is started, the ECM immediately transmits command signals to the AID to drive the air pump and ASV.

The AID outputs the ASV malfunction signal to the ECM if either: 1) the AID receives the command signal from the ECM to drive the ASV, but the AID output voltage to the ASV is low, or 2) the AID does not receive the command signal from the ECM to drive the ASV, but the AID output voltage to the ASV is high.

The ECM sets the ETC based on the diagnostic signal from the AID.

WIRING DIAGRAM

A01DWKWE02

INSPECTION PROCEDURE

Tech Tips

The diagnostic information output from the AID can be confirmed by connecting an oscilloscope to the diagnostic information terminal of the AID.

A01DYCSE44

  1. Connect the intelligent tester to the DLC3.

  2. Connect an oscilloscope probe to the AIDI terminal of the ECM.

  3. On the tester, select the following menu items: Powertrain / Engine and ECT / Data List.

  4. Start the engine and turn the tester ON.

  5. Monitor the output voltage of the AID (duty ratio signal).

Oscilloscope range
Item Content
Tester Connection AIDI - E1
Tool Setting 5 V/DIV., 20 to 40 msec./DIV.
Condition Idling
AID Diagnostic Signal Waveform ECM Command

DTC

(ECM Output)

 Suspected Trouble Area

100% Duty Ratio

See waveform 1

 Any Air Injection (AI) System operation P1613

  • Open in diagnostic signal circuit

  • Air Injection Control Driver (AID)

  • Open in AID +B circuit (AID power source)

  • Short between +B circuit and diagnostic signal circuit

0% Duty Ratio

See waveform 2

AI System: ON

(Air pump ON, ASV ON)

 P1613

  • Open or short in air pump or Air Switching Valve (ASV) command signal circuit (ECM - AID)

  • Open in AID ground circuit

  • Short between diagnostic signal circuit and body ground

  • AID

  • ECM

AI System: OFF

(Air pump OFF, ASV OFF)

 -

  • Normal

20% Duty Ratio

See waveform 3

 Air Pump: ON P0418

  • Short between air pump drive circuit and body ground

  • Harness & connector (AID - Pump)

  • Air Pump

  • AID

  • ECM
Air Pump: OFF P0418

  • Open in air pump drive circuit (AID - Pump), or short between air pump drive circuit and +B

  • Harness & connector (AID - Pump)

  • Air Pump

  • AID

  • ECM

40% Duty Ratio

See waveform 4

 ASV: ON P0412

  • Short between ASV drive circuit and body ground

  • Harness & connector (AID - ASV)

  • ASV

  • AID

  • ECM
ASV: OFF P0412

  • Open in ASV drive circuit (AID - ASV), or short between ASV drive circuit and +B

  • Harness & connector (AID - ASV)

  • AID

  • ASV

  • ECM

80% Duty Ratio

See waveform 5

AI System: OFF

(Air pump OFF, ASV OFF)

 P1613

  • AID

  • ECM

AI System: ON

(Air pump ON, ASV ON)

 -

  • Normal

Excluding Above

(excluding 0, 20, 40, 80, 100% duty)

 - P1613

  • AID

  • Open in AID ground circuit

  1. Waveform 1

    A01DWZ9E01

    • 100% Duty Ratio

  2. Waveform 2

    A01DZ5WE01

    • 0% Duty Ratio

  3. Waveform 3

    A01E2NHE01

    • 20% Duty Ratio

  4. Waveform 4

    A01DXF8E01

    • 40% Duty Ratio

  5. Waveform 5

    A01DW5DE01

    • 80% Duty Ratio

    Tech Tips

    Read freeze frame data using the intelligent tester. Freeze frame data records the engine conditions when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.

PROCEDURE


  1. INSPECT AIR SWITCHING VALVE

    A01E1LNE05

    1. Disconnect the A22 ASV connector.

    2. Measure the resistance of the ASV.

      Standard resistance
      Tester Connection Specified Condition
      1 - 2 3 to 10 Ω

    NG

    REPLACE AIR SWITCHING VALVE

    OK

  2. CHECK WIRE HARNESS (AIR SWITCHING VALVE - BODY GROUND)

    A01E2ZDE09

    1. Disconnect the A22 ASV connector.

    2. Measure the resistance of the wire harness side connector.

      Standard resistance
      Tester Connection Specified Condition
      A22-1 - Body ground Below 1 Ω

    NG

    REPAIR OR REPLACE HARNESS AND CONNECTOR

    OK

  3. CHECK WIRE HARNESS (AIR SWITCHING VALVE - AIR INJECTION CONTROL DRIVER)

    A01DZU3E02

    1. Disconnect the A22 ASV connector.

    2. Disconnect the A20 AID connector.

    3. Measure the resistance of the wire harness side connectors.

      Standard resistance
      Tester Connection Specified Condition
      A22-2 - A20-6 Below 1 Ω

    NG

    REPAIR OR REPLACE HARNESS AND CONNECTOR

    OK

    REPLACE AIR INJECTION CONTROL DRIVER