Inspection Procedure

HINT:

Read freeze frame data using Techstream. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air/fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.

INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)

Disconnect the A24 Air-Fuel Ratio (A/F) sensor connector.

Measure the resistance between the terminals of the A/F sensor connector.

Standard resistance

TESTER CONNECTIONS AND SPECIFIED CONDITIONS

Tester Connections	Specified Conditions
HT (1) - +B (2)	Between 1.8 Ω and 3.4 Ω at 20°C (68°F)
HT (1) - AF- (4)	10 kΩ or higher

Fig 1: Identifying A/F Sensor Connector Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Reconnect the A/F sensor connector.

NG: REPLACE AIR FUEL RATIO SENSOR

OK: Go to Next Step

INSPECT EFI RELAY

Remove the EFI relay from the engine room R/B.

Check the EFI relay resistance.

Standard resistance

TESTER CONNECTIONS AND SPECIFIED CONDITIONS

Tester Connections	Specified Conditions
3 - 5	10 kΩ or higher
3 - 5	Below 1 Ω (when battery voltage applied to terminals 1 and 2)

Fig 2: Identifying EFI Relay Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Reinstall the EFI relay.

NG: REPLACE EFI RELAY

OK: Go to Next Step

INSPECT ECM (HA1A VOLTAGE)

Turn the ignition switch to the ON position.

Measure the voltage between the terminals of the E4 ECM connector.

Standard voltage

TESTER CONNECTIONS AND SPECIFIED CONDITIONS

Tester Connections	Specified Conditions
HA1A (E4-5) - E04 (E4-7)	Between 9 V and 14 V

Fig 3: Identifying E4 ECM Connector Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

OK: REPLACE ECM

NG: Go to Next Step

CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ECM, EFI RELAY)

Check the harness and connector between the ECM and A/F sensor.

Disconnect the A24 A/F sensor connector.

Fig 4: Identifying A/F Sensor Connector And ECM Connector Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Disconnect the E4 ECM connector.

Check the resistance.

Standard resistance (Check for open)

TESTER CONNECTIONS AND SPECIFIED CONDITIONS

Tester Connections	Specified Conditions
HT (A24-1) - HA1A (E4-5)	Below 1 Ω

Standard resistance (Check for short)

TESTER CONNECTIONS AND SPECIFIED CONDITIONS

Tester Connections	Specified Conditions
HT (A24-1) or HA1A (E4-5) - Body ground	10 kΩ or higher

Reconnect the A/F sensor connector.
Reconnect the ECM connector.

Check the harness and connector between the A/F sensor and EFI relay.

Inspect the EFI2 fuse.
- Remove the EFI2 fuse from the engine room R/B.
- Check the EFI2 fuse resistance.
  Standard resistance: Below 1 Ω
- Reinstall the EFI2 fuse.
Disconnect the A24 A/F sensor connector.
Remove the EFI relay from the engine room R/B.

Check the resistance.

Fig 5: Identifying EFI Relay Location

Standard resistance (Check for open)

TESTER CONNECTIONS AND SPECIFIED CONDITIONS

Tester Connections	Specified Conditions
+B (A24-2) - EFI relay (3)	Below 1 Ω

Standard resistance (Check for short)

TESTER CONNECTIONS AND SPECIFIED CONDITIONS

Tester Connections	Specified Conditions
+B (A24-2) or EFI relay (3) - Body ground	10 kΩ or higher

Reconnect the A/F sensor connector.
Reinstall the EFI relay.

NG: REPAIR OR REPLACE HARNESS OR CONNECTOR

OK: REPLACE ECM