Where is the sensor for an OBD2 Code error P1155 for a Toyota Sienna 2001. How do you change it and what is the effect if you do not change it?

P1155: Air/Fuel Ratio Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)

The sensor is on the Bank 1 throttle body with electrical connection. Its a delicate sensor. Unscrew it from the throttle body and check if its dirty, spray it with electronic cleaner with care. If its damaged, just replace it.

If its not rectified, the car computer may default the air temperature to 20 degC and the air flow will not be correct and may have the following effect:

1. You might have difficulty in winter startups 2. Loss fuel efficiency (air/fuel ratio is messed up)/NOx problems/failed emission test/prematured catalytic converter replacement etc.

CLARIFICATION

An Air Fuel Ratio Sensor is also known as Wide Range Oxygen Sensor.

Bank 1 Sensor 1 is mounted in the exhaust header before the Catalytic Converter (CC). The ECU uses the signal from the AF sensor to adjust Air/Fuel ratio. On V6 and V8 engines there is a second AF Sensor in the other header. (Bank 2 Sensor 1).

After the CC there is a narrow range O2 sensor called Bank 1 Sensor 2. It monitors the CC. If there are two CCs there is a second O2 sensor (Bank 2 Sensor 2)

The AF Sensor draws about 3 amps so check connections. The heater is a resistor between the B+ and HT terminals of the plug. On V engines there is also a AF relay to check.

I found the above info else ware on the web. I have the code intermittently on my 2001 V6 Sienna. If I ever get a day off I am going to troubleshoot mine and will report the results.

PS I may have answered this twice. I think I lost the first one.

Here is a listing of Toyota Specific Diagnostic Trouble Codes

Code

Description

P1100

BARO Sensor Circuit.

P1120

Accelerator Pedal Position Sensor Circuit.

P1121

Accelerator Pedal Position Sensor Range/Performance Problem.

P1125

Throttle Control Motor Circuit.

P1126

Magnetic Clutch Circuit.

P1127

ETCS Actuator Power Source Circuit.

P1128

Throttle Control Motor Lock.

P1129

Electric Throttle Control System.

P1130

Air/Fuel Sensor Circuit Range/Performance. (Bank 1 Sensor 1)

P1133

Air/Fuel Sensor Circuit Response. (Bank 1 Sensor 1)

P1135

Air/Fuel Sensor Heater Circuit Response. (Bank 1 Sensor 1)

P1150

Air/Fuel Sensor Circuit Range/Performance. (Bank 1 Sensor 2)

P1153

Air/Fuel Sensor Circuit Response. (Bank 1 Sensor 2)

P1155

Air/Fuel Sensor Heater Circuit. (Bank 1 Sensor 2)

P1200

Fuel Pump Relay Circuit.

P1300

Igniter Circuit Malfunction - No. 1.

P1310

Igniter Circuit Malfunction - No. 2.

P1335

No Crankshaft Position Sensor Signal - Engine Running.

P1349

VVT System.

P1400

Sub-Throttle Position Sensor.

P1401

Sub-Throttle Position Sensor Range/Performance Problem.

P1405

Turbo Pressure Sensor Circuit.

P1406

Turbo Pressure Sensor Range/Performance Problem.

P1410

EGR Valve Position Sensor Circuit Malfunction.

P1411

EGR Valve Position Sensor Circuit Range/Performance.

P1500

Starter Signal Circuit.

P1510

Boost Pressure Control Circuit.

P1511

Boost Pressure Low.

P1512

Boost Pressure High.

P1520

Stop Lamp Switch Signal Malfunction.

P1565

Cruise Control Main Switch Circuit.

P1600

ECM BATT Malfunction

P1605

Knock Control CPU.

P1630

Traction Control System.

P1633

ECM.

P1652

Idle Air Control Valve Control Circuit.

P1656

OCV Circuit.

P1658

Wastegate Valve Control Circuit.

P1661

EGR Circuit.

P1662

EGR by-pass Valve Control Circuit.

P1780

Park/Neutral Position Switch Malfunction (Only For A/T)