TLDR: The sensor is difficult to check because the current change it produces is too small for most clamp meters, so you would have to cut the harness to test it. Not recommended. Try checking for bad connections first. If it's not those, and it's likely not the ECM as you would likely have other symptoms than just this, then try replacing the sensor itself. It is recommended you get a profesional diagnosis before parts swapping as the sensor can be very expensive. (as much as $400 USD).
This is directly from AutoCodes.com
The code is for an air/fuel ratio sensor heater circuit malfunction. The listed possible causes are:
- Faulty Air-Fuel Ratio (A/F) Sensor Bank 1 Sensor 1
- Air-Fuel Ratio (A/F) Sensor Bank 1 Sensor 1 harness is open or shorted
- Air-Fuel Ratio (A/F) Sensor Bank 1 Sensor 1 circuit poor electrical connection
- Faulty Engine Control Module (ECM)
Read more: http://www.autocodes.com/p1135_toyota_rav4_2.0.html#ixzz40d18jJnm
To quote the site:
"Air-Fuel Ratio (A/F)sensor need to reach a minimum operating
temperature of 1200 degrees F to produce an accurate voltage signal.
The faster the air-fuel ratio sensor reaches that temperature the
faster the sensor will start sending an accurate signal to the Engine
Control Module (ECM).
In order to achieve the require temperature, a heater element is
included inside the air-fuel ratio sensor. The ECM controls the
air-fuel ratio sensor heater element based on signals from the engine
coolant temperature and engine load. The ECM controls the heater
element circuit by allowing current flow to ground.
The ECM monitors the voltage signal received through the heater
element circuit and determines the state of the circuit by comparing
the voltage detected with the factory specifications."
This diagram is included to help you identify which bank is at fault:
The following is how to test an AFR (Air Fuel Ratio) sensor:
"As the ECM monitors the varying current, a special circuit (also
inside the PCM or Power-train Control Module) converts the current
into a voltage value and passes it on to the serial data stream as a
scanner PID. This is why the best way to test an AFR sensor’s signal
is by monitoring the voltage conversion circuitry, which the ECM sends
out as an AFR-voltage PID. It is possible to monitor the actual AFR
sensor varying current, but the changes are very small (in the low
milliamp range) and difficult to monitor. A second drawback to a
manual AFR current test is that the signal wire has to be cut or
broken to connect the ammeter in series with the pump circuit. Today’s
average clamp-on ammeter is not accurate enough at such a small scale.
For this reason, the easiest (but not the only) way to test an AFR
sensor is with the scanner. By using a scanner to communicate with the
ECM, one can view AFR sensor activity. This data is typically
displayed as WRAF, A/F, or AFR sensor voltage. However, on some
vehicles and scanners it will show up as "lambda" or "equivalence
ratio." If the PID displays a voltage reading, it should be equal to
the sensor's reference voltage when the air/fuel mixture is ideal. The
reference voltage varies from car to car, but is often 3.3 V or 2.6 V.
When the fuel mixture becomes richer (on a sudden, quick
acceleration), the voltage should decrease. Under lean conditions
(such as deceleration) the voltage should increase. If the scanner PID
displays a "lambda" or "equivalence ratio," the reading should be 1.0
under stoichiometric conditions. Numbers above 1.0 indicate a lean
condition while numbers below 1.0 indicate rich mixtures. The ECM uses
the information from the sensors to adjust the amount of fuel being
injected into the engine, so corresponding changes in the short-term
fuel trim PID(s) should also be seen. Lean mixture readings from the
AFR sensor will prompt the ECM to add fuel, which will manifest itself
as a positive (or more positive) short-term fuel trim percentage. Some
technicians will force the engine to run lean by creating a vacuum
leak downstream from the mass airflow sensor, and then watch scanner
PIDs for a response. The engine can be forced rich by adding a metered
amount of propane to the incoming airflow. In either case, if the
sensor does not respond, it likely has a problem. However, these tests
do not rule out other circuitry problems or ECM issues. Because an AFR
sensor can be relatively expensive (up to $400 U.S dollars), a
professional diagnosis is recommended."
This is from here:
The electrical issues about open harness or poor electrical connection can be checked by using an ohmmeter to "buzz out" (check for conductivity) between the two connectors on the harness. Also look for any corrosion on the connectors themselves.