P0412

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

DESCRIPTION

DTC Detection Conditions (Part 1):

DTC Detection Conditions (Part 2):

The Secondary Air Injection (AIR) system consists of an air pump, the Air Switching Valve (ASV), a pressure sensor, the Air Injection Control Driver (AID) and the ECM. For a short time after cold engine starts, the AIR system pumps secondary air to the exhaust port of the cylinder head to purify the exhaust emissions. The secondary air is supplied by the air pump and is pumped to the exhaust port through the ASV.

The AID drives the ASV and the air pump according to command signals transmitted by the ECM. The pressure sensor detects the pressure in the secondary air passage when the AIR system is ON and OFF, and transmits pressure signal to the ECM.

The AID is not only equipped to drive the pump and valve, but also with a diagnosis function to detect malfunctions in the AIR system circuit.

HINT: As a large current is required to drive the air pump and ASV, an AID has been added to the previous system.

MONITOR DESCRIPTION

Monitor Strategy:

Typical Enabling Conditions:

Typical Malfunction Thresholds:

Component Operating Range:

The Air Injection Control Driver (AID) detects open and short circuits according to the voltages of the air pump terminal (VB) and the Air Switching Valve (ASV) terminal (VV), and transmits diagnostic information as a signal to the ECM.

For a short time after cold engine starts, the ECM transmits command signals to the AID to drive the air pump and ASV.

The AID transmits an ASV malfunction signal to the ECM if either of the following conditions is met:
- The voltage at the AID terminal relating to the ASV is low despite the AID receiving command signals from the ECM to drive the ASV.
- The voltage at the AID terminal relating to the ASV is high despite the AID receiving no command signals from the ECM to drive the ASV.

The ECM sets the DTC based on diagnostic signals from the AID.

Wiring Diagram:

INSPECTION PROCEDURE

HINT: Diagnostic information output by the AID can be confirmed by connecting an oscilloscope to the diagnostic information terminal of the AID. Reading the waveform while performing the AIR system intrusive operation provided in the SYSTEM CHECK function, allows the possible trouble areas to be narrowed down.

a. Start the engine and warm it up.
b. Turn the ignition switch to OFF.
c. Connect an intelligent tester to the DLC3.
d. Connect oscilloscope probes to the AIDI and E1 terminals of the ECM.
e. Turn the ignition switch to ON and turn the tester ON.
f. Select the following menu items: DIAGNOSIS/ENHANCED OBD II/SYSTEM CHECK/AIR INJ CHECK/MANUAL OPERATION/AP: ON, ASV: OPEN and AP: OFF, ASV CLOSE.

HINT: When MANUAL OPERATION is selected, the tester initialization (atmospheric pressure measurement) is performed automatically. The initialization takes 10 seconds. After the initialization, AP and ASV operation can be selected.

g. Start the engine.
h. Perform the AIR system intrusive operation while the engine is idling.

Oscilloscope Waveform:

i. Monitor the AID voltage output (duty ratio signal).
j. Turn the ignition switch to OFF.

NOTE:
- This AIR INJECTION CHECK only allows technicians to operate the AIR system for a maximum of 5 seconds. Furthermore, the check can only be performed up to 4 times per trip. If the test is repeated, intervals of at least 30 seconds are required between checks. While AIR system operation using the intelligent tester is prohibited, the tester display indicates the prohibition (WAIT or ERROR). If an ERROR as shown in the illustration is displayed on the tester during the test, stop the engine for 10 minutes, and then try again.
- Performing the AIR INJ CHECK repetitively may cause damage to the AIR system. If necessary, leave an interval of several minutes between SYSTEM CHECK operations to prevent the system from overheating.
- When performing the AIR INJ CHECK operation after the battery cable has been reconnected, wait for 7 minutes with the ignition switch turned to ON or the engine running.
- Turn the ignition switch to OFF when the AIR INJ CHECK operation finishes.

Oscilloscope Waveforms:

HINT:
- By using an intelligent tester to perform the AIR INJ CHECK operation in the SYSTEM CHECK, the air-fuel ratio and the pressure in the secondary air injection system passage can be checked while the secondary air injection system is operating. This helps technicians to troubleshoot the system when it malfunctions.
- Read freeze frame data using an intelligent tester. Freeze frame data record the engine condition 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.