3MZ-FE ENGINE CONTROL SYSTEM – SFI SYSTEM ES–85

Oxygen Sensor Heater Control Circuit Low

DTC P0037
(Bank 1 Sensor 2)

Oxygen Sensor Heater Control Circuit High

DTC P0038
(Bank 1 Sensor 2)

Oxygen Sensor Heater Control Circuit Low

DTC P0057
(Bank 2 Sensor 2)

Oxygen Sensor Heater Control Circuit High

DTC P0058 ES
(Bank 2 Sensor 2)
DESCRIPTION
Refer to DTC P0136 (See page ES-125).
HINT:
The ECM provides a pulse width modulated control circuit to adjust current through the heater. The
heated oxygen sensor heater circuit uses a relay on the +B side of the circuit.
Reference (Bank 1 Sensor 2 System Drawing)

Heated Oxygen Sensor ECM

EFI MAIN Relay
Heater
From Battery HT1B
EFI No. 1 Fuse EFI No. 2 Fuse Sensor
OX1B

E2

MREL

A078428E02

DTC No. DTC Detection Condition Trouble Area

• Open or short in heater circuit of the heated oxygen
Heater current is 0.3 A or less when the heater sensor
P0037
operates with +B greater than 10.5 V (1 trip detection • Heated oxygen sensor heater
P0057
logic) • EFI MAIN relay
• ECM
• Open or short in heater circuit of the heated oxygen
sensor
P0038 Heated current exceeds 2 A when the heater operates
• Heated oxygen sensor heater
P0058 (1 trip detection logic)
• EFI MAIN relay
• ECM

HINT:
• Bank 1 is the bank that includes cylinder No.1.
• Bank 2 is the bank that does not include cylinder No.1.
• Sensor 1 is the closest sensor to the engine assembly.
• Sensor 2 is the farthest sensor away from the engine assembly.
 ES–86 3MZ-FE ENGINE CONTROL SYSTEM – SFI SYSTEM

MONITOR DESCRIPTION
The sensing portion of the heated oxygen sensor has a zirconia element that is used to detect oxygen
concentration in the exhaust. If the zirconia element is at the proper temperature and the difference in the
oxygen concentration between the inside and outside surfaces of the sensor is large, the zirconia element
will generate voltage signals. In order to increase the oxygen concentration detecting capacity in the
zirconia element, the ECM supplements the heat from the exhaust with heat from a heating element
inside the sensor. When the current in the sensor is out of the standard operating range, the ECM
interprets this as a fault in the heated oxygen sensor and sets a DTC.
Example:
The ECM will set a high current DTC if the current in the sensor is more than 2 A when the heater is OFF.
Similarly, the ECM will set a low current DTC if the current is less than 0.3 A when the heater is ON.

MONITOR STRATEGY
ES P0037: Heated oxygen sensor heater (Bank 1) open/short (Low electrical current)
P0038: Heated oxygen sensor heater (Bank 1) open/short (High electrical current)
Related DTCs
P0057: Heated oxygen sensor heater (Bank 2) open/short (Low electrical current)
P0058: Heated oxygen sensor heater (Bank 2) open/short (High electrical current)
Required sensors / components Heated oxygen sensor heater (Bank 1 and 2)
Required sensors / components Vehicle Speed Sensor
Frequency of operation Continuous
Heated oxygen sensor heater (Bank 1) open/short (Low electrical current) : 0.5
seconds
Heated oxygen sensor heater (Bank 2) open/short (Low electrical current) : 0.5
seconds
Duration
Heated oxygen sensor heater (Bank 1) open/short (High electrical current) : 0.2
seconds
Heated oxygen sensor heater (Bank 2) open/short (High electrical current) : 0.2
seconds
MIL operation Immediate
Sequence operation None

TYPICAL ENABLING CONDITIONS

All:
Monitor run whenever following DTCs are not present None

P0037, P0057:
Battery voltage 10.5 V or more
Engine Running
Starter OFF
All heater is turned OFF and intrusive heating is operated
(a) and (b)
when the following conditions are met
(a) Heater ON
(b) Heater current Less than 0.3 A

P0038, P0058 Case 1:

Battery voltage 10.5 V or more
Engine Running
Starter OFF
Intrusive heating Not operating

P0038 and P0058 Case 2:

Battery voltage 10.5 V or more
All heater is turned OFF and intrusive heating is operated
(a) and (b)
when the following conditions are met
(a) Heater ON
 3MZ-FE ENGINE CONTROL SYSTEM – SFI SYSTEM ES–87

(b) Hybrid IC high current limiter port Fail

TYPICAL MALFUNCTION THRESHOLDS

P0037 and P0057:
Heated oxygen sensor heater current during intrusive
Less than 0.3 A
heating

P0038 and P0058 Case 1:

Hybrid IC high current limiter port Fail

P0038 and P0058 Case 2:

Heated oxygen sensor heater current during intrusive
More than 2 A
heating

ES
COMPONENT OPERATING RANGE
HO2S heater current 0.4 to 1 A (at idle, warmed-up engine and +B: 11 to 14 V)

MONITOR RESULT
Refer to "Checking Monitor Status" for detailed information (See page ES-14 ).
The test value and test limit information are described as shown in the following table. Check the monitor
result and test values after performing the monitor drive pattern (See page ES-16).
• TID (Test Identification Data) is assigned to each emissions-related component.
• TLT (Test Limit Type):
If TLT is 0, the component is malfunctioning when the test value is higher than the test limit.
If TLT is 1, the component is malfunctioning when the test value is lower than the test limit.
• CID (Component Identification Data) is assigned to each test value.
• Unit Conversion is used to calculate the test value indicated on generic OBD ll scan tools.
TID $04: HO2S heater
TLT CID Unit Conversion Description of Test Data Description of Test Limit
Multiply by 0.000076 Maximum HO2S heater current
1 $02 Malfunction threshold for HO2S heater
(A) (Bank 1 Sensor 2)
Multiply by 0.000076 Maximum HO2S heater current
1 $20 Malfunction threshold for HO2S heater
(A) (Bank 2 Sensor 2)

WIRING DIAGRAM
Refer to DTC P0136 (See page ES-130).

HINT:
• If DTCs related to different systems that have terminal E2 as the ground terminal are output
simultaneously, terminal E2 may have an open circuit.
• Read freeze frame data using the intelligent tester or the OBD II scan tool. The ECM records vehicle
and driving condition information as freeze frame data the moment a DTC is stored. When
troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, 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.
 ES–88 3MZ-FE ENGINE CONTROL SYSTEM – SFI SYSTEM

1 INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)

(a) Disconnect the H11 or H20 heated oxygen sensor

Component Side:
connector.
H20 Bank 1 H11 Bank 2 (b) Measure the resistance of the heated oxygen sensor
HT1B terminals.
+B +B HT Standard resistance (bank 1, 2 sensor 2)
Tester Connection Condition Specified Condition
H11-1 (HT) - H11-2 (+B)
E1 OX1B E1 OX
H20-1 (+B) - H20-2 20°C (68°F) 11 to 16 Ω
Front View (HT1B)

ES A082391E01

NG REPLACE HEATED OXYGEN SENSOR

OK

2 INSPECT EFI MAIN RELAY

(a) Remove the EFI MAIN relay from the engine room J/B.
(b) Measure the resistance of the EFI MAIN relay.
Standard resistance
Tester Connection Specified Condition
1-2 Below 1 Ω
3-5 10 kΩ or higher
Continuity
3-5
(when battery voltage is applied to terminals 1 and 2)

B016200
NG REPLACE EFI MAIN RELAY

OK

3 INSPECT ECM (HT1B OR HT2B VOLTAGE)

(a) Turn the ignition switch ON.

E2 (-) HT1B (+) HT2B (+) (b) Measure the voltage of the ECM connectors.
Standard voltage
Tester Connection Specified Condition
E9-25 (HT1B) - E8-28 (E2)
9 to 14 V
E9-33 (HT2B) - E8-28 (E2)

HINT:
E8 ECM E9 ECM • The HT1B stands for the heated oxygen sensor bank
A076903E53
1 sensor 2.
• The HT2B stands for the heated oxygen sensor bank
2 sensor 2.
OK REPLACE ECM

NG
 3MZ-FE ENGINE CONTROL SYSTEM – SFI SYSTEM ES–89

4 CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - ECM, HEATED

OXYGEN SENSOR - EFI RELAY)

(a) Check the wire harness between the ECM and heated
Wire Harness Side: oxygen sensor.
(1) Disconnect the E9 ECM connector.
Heated Oxygen Sensor Connector (2) Disconnect the H11 or H20 heated oxygen sensor
connector.
HT1B HT +B (3) Measure the resistance of the wire harness side
+B connectors.
Standard resistance
OX1B E2 E2
H20 Bank 1
OX
H11 Bank 2
Tester Connection
H20-2 (HT1B) - E9-25 (HT1B)
Specified Condition
ES
Below 1 Ω
Front View H11-1 (HT) - E9-33 (HT2B)
H20-2 (HT1B) or E9-25 (HT1B) - Body ground
10 kΩ or higher
H11-1 (HT) or E9-33 (HT2B) - Body ground

E9 (b) Check the wire harness between the heated oxygen

sensor and EFI MAIN relay.
(1) Disconnect the H11 or H20 heated oxygen sensor
connector.
HT1B
(2) Remove the EFI MAIN relay from the engine room
HT2B ECM Connector J/B.
(3) Measure the resistance of the wire harness side
Engine Room R/B and connectors.
Fusible Link Block: Standard resistance
Tester Connection Specified Condition
H11-2 (+B) - EFI relay terminal 3
Below 1 Ω
H20-1 (+B) - EFI relay terminal 3
H11-2 (+B) or EFI relay terminal 3 - Body ground
10 kΩ or higher
H20-1 (+B) or EFI relay terminal 3 - Body ground
EFI MAIN
Relay NG REPAIR OR REPLACE HARNESS OR
EFI No. 2 CONNECTOR
A124286E01

OK

REPLACE ECM