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

The Secondary Air Injection (AIR) system pumps air to the exhaust port to accelerate the activation of the catalyst. The secondary air injection system consists of the ECM, air pump, Air Switching Valve (ASV) (EASV), Air Switching Valve No. 2 (ASV No. 2) (ASV1, 2), pressure sensor and Air Injection Control Driver (AID). The Air Switching Valve (ASV) (EASV) is an electromagnetic type and Air Switching Valve No. 2 (ASV No. 2) (ASV1, 2) is a vacuum type.

The secondary air injection system pumps pressurized air to the exhaust port by the air pump through the ASV and ASV No. 2. The ASV assists the ASV No. 2. The ASV No. 2 also controls air supply.

The ECM sends signals to the AID, and then the AID operates the air pump and ASV. The pressure sensor detects pressure and exhaust pulsation in the system when the system operates and when it does not operate, and sends the data to the ECM.

Fig 1: Identifying Secondary Air Injection (AIR) Flow Diagram
G05264079Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
DTC DETECTION CONDITION TABLE

DTC No. DTC Detection Condition Trouble Area
P0412 Both of the following conditions are met when engine is idling just after cold start
(1 trip detection logic):
  1. Air injection (AIR) system does not operate (Air pump OFF and all ASVs OFF)
  2. Air injection control driver (AID) diagnostic signal duty is 40%
  • Open in air switching valve drive circuit
  • Short between air switching valve circuit and +B circuit
  • Air injection control driver (AID)
  • Air switching valve (ASV)
  • ECM
P0412 Both of the following conditions are met when engine is idling just after cold start
(1 trip detection logic):
  1. Air injection (AIR) system operates (Air pump ON and all ASVs ON)
  2. Air injection control driver (AID) diagnostic signal duty is 40%
  • Short between air switching valve circuit and body ground
  • AID
  • ASV
  • ECM