Toyota Tundra. Manual - part 1159

NG : REPAIR OR REPLACE HARNESS OR CONNECTOR

Fig. 45: Identifying D33*1 Or D34*2 A/F Sensor Heater Relay (A/F) Connector Terminals

OK : CHECK ECM POWER SOURCE CIRCUIT (See ECM POWER SOURCE CIRCUIT )

DTC P0037 OXYGEN SENSOR HEATER CONTROL CIRCUIT LOW (BANK 1 SENSOR 2); DTC
P0038 OXYGEN SENSOR HEATER CONTROL CIRCUIT HIGH (BANK 1 SENSOR 2); DTC P0057
OXYGEN SENSOR HEATER CONTROL CIRCUIT LOW (BANK 2 SENSOR 2); DTC P0058
OXYGEN SENSOR HEATER CONTROL CIRCUIT HIGH (BANK 2 SENSOR 2); DTC P0141
OXYGEN SENSOR HEATER CIRCUIT MALFUNCTION (BANK 1 SENSOR 2); DTC P0161
OXYGEN SENSOR HEATER CIRCUIT MALFUNCTION (BANK 2 SENSOR 2)

DESCRIPTION

D33-2 (+B) or 1A-4 - Body ground Always

10 kohms or higher

D34-2 (+B) or 1A-4 - Body ground Always

10 kohms or higher

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (1GR-FE) - Tundra

Refer to DTC P0136 .

HINT:



Sensor 2 refers to the sensor mounted behind the Three-Way Catalytic Converter (TWC) and located far
from the engine assembly.



When any of these DTCs are set, the ECM enters fail-safe mode. The ECM turns off the Heated Oxygen
(HO2) sensor heater in fail-safe mode. Fail-safe mode continues until the ignition switch is turned OFF.



The ECM provides a pulse width modulated control circuit to adjust the current through the heater. The
HO2 sensor heater circuit uses a relay on the +B side of the circuit.

Fig. 46: Oxygen Sensor Heater Control Circuit Diagram

DTC TROUBLE DETECTION CONDITION CHART

DTC

No.

DTC Detection Condition

Trouble Area

P0037
P0057

Heated Oxygen (HO2) sensor (bank 1, 2 sensor 2)
heater current less than 0.3 A (1 trip detection logic)



Open in HO2 sensor (bank 1, 2
sensor 2) heater circuit



HO2 sensor (bank 1, 2 sensor 2)
heater



EFI NO. 2 fuse



ECM

P0038
P0058

Heated Oxygen (HO2) sensor (bank 1,2 sensor 2) heater
current more than 2 A (1 trip detection logic)



Short in HO2 sensor (bank 1,2
sensor 2) heater circuit



HO2 sensor (bank 1, 2 sensor 2)
heater



EFI NO. 2 fuse



ECM

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (1GR-FE) - Tundra

HINT:



Bank 1 refers to the bank that includes No. 1 cylinder.



Bank 2 refers to the bank that does not include No. 1 cylinder.



Sensor 1 refers to the sensor closest to the engine assembly.



Sensor 2 refers to the sensor farthest away from the engine assembly.

MONITOR DESCRIPTION

The sensing portion of the Heated Oxygen (HO2) sensor has a zirconia element which is used to detect the
oxygen concentration in the exhaust gas. If the zirconia element is at the appropriate temperature, and the
difference between the oxygen concentrations surrounding the inside and outside surfaces of the sensor is large,
the zirconia element generates voltage signals. In order to increase the oxygen concentration detecting capacity
of the zirconia element, the ECM supplements the heat from the exhaust with heat from a heating element
inside the sensor.

Heated oxygen sensor heater range check (P0037, P0038, P0057 and P0058)

The ECM monitors the current applied to the O2 sensor heater to check the heater for malfunctions. If the
current is below the threshold value, the ECM will determine that there is an open circuit in the heater. If the
current is above the threshold value, the ECM will determine that there is a short circuit in the heater.

Example:

The ECM sets DTC P0038 or P0058 when the current in the HO2 sensor heater is more than 2 A. Conversely,
when the heater current is less than 0.3 A, DTC P0037 or P0057 is set.

Heated oxygen sensor heater performance (P0141 and P0161)

After the accumulated heater ON time exceeds 100 seconds, the ECM calculates the heater resistance using the
battery voltage and the current applied to the heater. If the resistance is above the threshold value, the ECM will
determine that there is a malfunction in the HO2S heater and set DTC P0141 and P0161.

MONITOR STRATEGY

P0141
P0161

Cumulative heater resistance correction value exceeds
the acceptable threshold (2 trip detection logic)



Open or short in HO2 sensor
(bank 1,2 sensor 2) heater circuit



HO2 sensor (bank 1, 2 sensor 2)
heater



EFI NO. 2 fuse



ECM

P0037: Heated oxygen sensor heater (bank 1 sensor 2) open/short
(Low electrical current)

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (1GR-FE) - Tundra