DTC P2A00: A/F Sensor Circuit Slow Response (Bank 1 Sensor 1); DTC P2A03: A/F Sensor Circuit Slow Response (Bank 2 Sensor 1): Procedure

WARNING: This page is about a different car, the 2009 Lexus IS 350. However, it is still accessible from the selected car via links, so may be relevant.

CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P2A00 AND/OR P2A03)

Connect Techstream to the DLC3.
Turn the engine switch on (IG).
Turn the tester on.
Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

Read DTCs.

Result

Display (DTC Output)	Proceed to
P2A00 and/or P2A03	A
P2A00 and/or P2A03 and other DTCs	B

HINT:

If any DTCs other than P2A00 or P2A03 are output, troubleshoot those DTCs first.

B → GO TO DTC CHART

A: Go to next step

INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

Fig 1: Identifying Connector Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Disconnect the E42 or E38 A/F sensor connector.

Measure the resistance according to the value(s) in the table below.

Standard resistance (Bank 1 sensor 1)

Tester Connection	Condition	Specified Condition
HA1A (1) - +B (2)	20°C (68°F)	1.8 Ω to 3.4 Ω
HA1A (1) - A1A- (4)	-	10 kΩ or higher

Standard resistance (Bank 2 sensor 1)

Tester Connection	Condition	Specified Condition
HA2A (1) - +B (2)	20°C (68°F)	1.8 Ω to 3.4 Ω
HA2A (1) - A2A- (4)	-	10 kΩ or higher

Reconnect the A/F sensor connector.

NG → REPLACE AIR FUEL RATIO SENSOR

OK: Go to next step

CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM)

Disconnect the E42 and E38 A/F sensor connector.

Fig 2: Identifying Connector Terminals
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Turn the engine switch on (IG).

Measure the voltage according to the value(s) in the table below.

Standard voltage

Tester Connection	Specified Condition
+B (E42-2) - Body ground	9 to 14 V
+B (E38-2) - Body ground	9 to 14 V

Turn the engine switch off.
Disconnect the E6 ECM connector.

Measure the resistance according to the value(s) in the table below.

Standard resistance (Check for open)

Tester Connection	Specified Condition
HA1A (E42-1) - HA1A (E6-6)	Below 1 Ω
A1A+ (E42-3) - A1A+ (E6-18)	Below 1 Ω
A1A- (E42-4) - A1A- (E6-17)	Below 1 Ω
HA2A (E38-1) - HA2A (E6-4)	Below 1 Ω
A2A+ (E38-3) - A2A+ (E6-28)	Below 1 Ω
A2A- (E38-4) - A2A- (E6-27)	Below 1 Ω

Standard resistance (Check for short)

Tester Connection	Specified Condition
HA1A (E42-1) or HA1A (E6-6) - Body ground	10 kΩ or higher
A1A+ (E42-3) or A1A+ (E6-18) - Body ground	10 kΩ or higher
A1A- (E42-4) or A1A- (E6-17) - Body ground	10 kΩ or higher
HA2A (E38-1) or HA2A (E6-4) - Body ground	10 kΩ or higher
A2A+ (E38-3) or A2A+ (E6-28) - Body ground	10 kΩ or higher
A2A- (E38-4) or A2A- (E6-27) - Body ground	10 kΩ or higher

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

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR

OK: Go to next step

PERFORM CONFIRMATION DRIVING PATTERN
NEXT: Go to next step

CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00 AND/OR P2A03)

Read DTCs using Techstream.

Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

Result

Display (DTC Output)	Proceed to
P2A00 and/or P2A03	A
No output	B

B → REPLACE ECM

A: Go to next step

REPLACE AIR FUEL RATIO SENSOR
NEXT: Go to next step
PERFORM CONFIRMATION DRIVING PATTERN
NEXT: Go to next step

CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00 AND/OR P2A03)

Read DTCs using Techstream.

Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

Result

Display (DTC Output)	Proceed to
No output	A
P2A00 and/or P2A03	B

B → REPLACE ECM

A → END