In this tutorial I'm gonna' explain how to test the internal heater of oxygen sensor #2 of the 1994 3.0L V6 Ford Ranger (Mazda B3000).
Testing the O2 sensor #2's heater element involves checking for power, Ground and the internal resistance of the heater itself. To perform these 3 simple tests all you'll need is a multimeter.
Contents of this tutorial at a glance:
You can find this tutorial in Spanish here: Calentador Del Sensor De Oxígeno N.º 2 (1994 3.0L Ford Ranger) (at: autotecnico-online.com).
You can find the 1994 3.0L Ford Ranger (Mazda B3000) oxygen sensor #1 heater test here: O2 Sensor #1 Heater Element Test (1994 3.0L Ford Ranger And Mazda B3000).
NOTE: You can find the oxygen sensor circuit diagram here: Oxygen Sensor Circuit Diagram (1994 3.0L Ford Ranger And Mazda B3000).
Oxygen Sensor #2 Basics
Your 1994 3.0L V6 Ford Ranger (Mazda B3000) comes equipped with two heated oxygen sensors.
This tutorial deals with oxygen sensor #2. This bad boy is located on the driver side the engine. This sensor measures the oxygen content of the exhaust for bank 2. Bank 2 consists of cylinders 4, 5, and 6.
The heater, inside the O2 sensor, gets the sensor to heat up faster and activate sooner. For the heater to work, it needs power in the form of 10 to 12 Volts DC and a Ground source.
Power is provided by fuse #18 of the dash fuse box by the light blue with orange stripe wire. Power is only available when the ignition key is in the RUN position.
Ground is available at all times since the Ground wire connects directly to your Ranger's chassis.
TEST 1: Making Sure That Power Is Present
The heater element of the number 2 oxygen sensor needs power in the form of 10 to 12 Volts to activate.
The very first test that we're gonna' do is to make sure that the light blue with orange stripe (LT BLU/ORG) wire has power.
We're going to do a simple multimeter voltage test to find out if this voltage is present or not.
CAUTION: Perform all tests with a completely cold engine!
These are the test steps:
Disconnect O2 sensor #2 from its engine wiring harness connector.
Locate the LT BLU/ORG wire of the engine wiring harness oxygen sensor connector.
With your multimeter in Volts DC mode, probe the LT BLU/ORG with the red multimeter test lead.
Ground the black multimeter test lead directly on the battery's negative (-) terminal.
With the Key On Engine Off (KOEO), the LT BLU/ORG wire should have 10 to 12 Volts DC.
Let's interpret your multimeter voltage test result:
CASE 1: Power is available at the LT BLU/ORG wire. This is the correct test result.
The next step is to make sure that the o2 sensors heater is getting Ground. For this test go to: TEST 2: Making Sure That Ground Is Present.
CASE 2: Power IS NOT available at the LT BLU/ORG wire. Without power the O2 sensor's heater is not going to work.
A lack of power usually is a result of one of two things: a blown fuse or an open in the LT BLU/ORG wire between the O2 connector and the dash fuse box.
The following circuit diagram of the oxygen sensor will help you further diagnose these missing 12 Volts: Oxygen Sensor Circuit Diagram (1994 3.0L Ford Ranger And Mazda B3000).