These Diagnostic Trouble Codes (DTC P0135 & P0141) relate to the heater element in the Oxygen Sensor (HO2S) sometimes referred to as an Airflow Sensor. P0135 is in the Bank 1 Sensor 1 position. This location is pre-catalyst and typically on the right bank of a v6 or v8 engine or near the front of a dual banked 4 cylinder (eg: Rav). The P0141 is the post catalyst sensor in the Bank 1 Sensor 2 position. These stored Diagnostic Trouble Codes (DTC P0135 & P0141) are not definitive enough to just replace the part based upon its’ indication.
Using Heated Oxygen Sensors (HO2S) in the pre-catalyst position allows the engine to enter closed loop faster which increases performance, increases fuel economy and decreases emissions.
Using Heated Oxygen Sensors (HO2S) in the post-catalyst position insures heat is maintained for proper catalyst monitoring.
When the key is turned on, battery power is applied typically to a 4 terminal relay from the main power relay. The relay also receives power on another terminal on the relay. If the conditions are present (cold temperature, cold start, etc) as monitored by the Powertrain Control Module (PCM), the Powertrain Control Module (PCM) applies a ground for the relay. The relay now sends power to the Heated Oxygen Sensor (HO2S) heater element and it completes the circuit to chassis ground.
On a cold start the Powertrain Control Module (PCM) monitors the coolant temperature, the air flow into the engine and the amount of time required for the Heated Oxygen Sensor (HO2S) to start cycling. If it takes too long the PCM sets the code and turns on the Malfunction Indicator Lamp (MIL).
To perform the job correctly you should look at the items that could have caused the reported failure of the sensor. This would include an inspection of the basic items, such as air filter, loose or broken air duct tubing, vacuum leaks, malfunctioning Positive Crankcase Ventilation (PCV) system, lack of maintenance, etc.
You should check for Technical Service Bulletins (TSB) including those that address the possible need to reprogram the Powertrain Control Module (PCM) that may relate to the Diagnostic Trouble Code (DTC P0135 & P0141). If it needs reprogrammed that can be performed with J2534 tools such as ours.
Before replacing a sensor as a defective, you should check all the fuses, check power available at the heater relays and check relay operation. As a last test check for power and ground at the heater electrical connector.
Fix It Right The First Time!
Fortunately, everything you need everything you need to fix it right the first time is right here!
To access the sensor and data from your Engine Controller (PCM) you will need:
Professional Quality Scan Tool such as our 2X80S Scan Tool series.
If you understand how the systems were designed to work and how to test them, great! Otherwise you will need factory product service training manuals that will teach you and guide you through the diagnostic phase.
You might also need the manufacturer factory service manuals and data systems that provide specifications and details relative to your specific model.
Or aftermarket data systems such as All Data, Mitchell On Demand, Auto Data, Bosch, and others.
Everything is available here for you as a single source for all your needs. The aftermarket data systems are available in our members only area by direct shipment from the distributor at great pricing.