Oxygen Sensor Heater Test -P0135 (1.6L Suzuki Sidekick, Geo Tracker)

Testing the front oxygen sensor's heater, located before the catalytic converter and which causes a P0135 trouble code when it fails, is not hard.

In this tutorial I'll show you how to test the front O2 sensor heater, on your 1.6L Suzuki Sidekick (1.6L Geo Tracker) with a simple multimeter resistance test.

Here are the contents of this tutorial:

  1. Circuit Descriptions of the Upstream Oxygen Sensor.
  2. TEST 1: Verifying Power and Ground to the Heater.
  3. TEST 2: Testing the Heater Element's Resistance.
  4. Where to Buy the Oxygen Sensor and Save Some $$$.
  5. More 1.6L Suzuki Tutorials.

NOTE: The 1996 thru' 1998 1.6L Suzuki Sidekick has 2 oxygen sensors. One before and one after the catalytic converter. If you need to test the rear oxygen sensor's heater (or a P0141 trouble code) see this tutorial: Oxygen Sensor Heater Test -P0141 (1996-1998 1.6L Suzuki Sidekick).

Circuit Descriptions of
the Upstream Oxygen Sensor

Oxygen Sensor Heater Test -P0135 (1.6L Suzuki Sidekick, Geo Tracker)

Testing trouble code P0135: Heated Oxygen Sensor Circuit Malfunction Bank 1 Sensor 1 involves making sure that the front O2 sensor's heater is getting power and ground. Then, making sure that it's internal resistance is within specification.

To accomplish these tests, you'll need to know what wires of the O2 sensor connector and its engine wiring harness connector are going to be tested. Here are the basics:

  1. The connector on the O2 sensor itself has male spade terminals.
  2. The engine wiring harness connector has female terminals.
  3. To check for power and ground, we'll test the engine wiring harness O2 connector.
  4. To test the O2 sensor heater's internal resistance we'll test the connector on the O2 sensor itself.

The illustration I'm using throughout this tutorial is the connector of the O2 sensor itself.

Here's a brief description of the 4 wires of the front oxygen sensor:

Front Oxygen Sensor Pinout
(1996-1998 1.6L Suzuki Sidekick)
Pin Wire Color Description
1 GRY/YEL or BRN O2 Signal Ground
2 WHT (1996)
RED/BLU (1997, 1998)
O2 Signal
3 PNK Heater Power (-)
4 BLK/WHT Heater Power (+)

TEST 1: Verifying Power and Ground to the Heater

Oxygen Sensor Heater Test -P0135 (1.6L Suzuki Sidekick, Geo Tracker)

To get our testing under way, we'll start by making sure that the pre-catalytic converter oxygen sensor is getting both power and ground. Without these 2 the O2 sensor's heater won't activate and heat up.

The wire that supplies power (12 Volts) is the black with white stripe (BLK/WHT) wire of the engine wiring harness O2 sensor connector. Remember that the engine wiring harness connector has female terminals.

The wire that supplies ground is the pink (PNK) wire of the engine wiring harness O2 sensor connector.

CAUTION: The oxygen sensor gets and stays very hot even after the engine is off! Perform this test with a completely cold engine. Be careful and take all necessary safety precautions! If you raise your vehicle with a jack, place it on jack stands!

IMPORTANT: The illustration above is of the connector on the oxygen sensor itself. To check for power and ground, you'll test the wires of the engine wiring harness O2 sensor connector.

OK, this is what you'll need to do:

  1. 1

    Verify that the black with white strip (BLK/WHT) wire has voltage (10 to 12 Volts DC ) with the key on but engine off.

    Connect the red multimeter test lead (using the appropriate tool) to the BLK/WHT wire. Connect the black multimeter test lead to the negative battery terminal.

    Your multimeter should read 10 to 12 Volts DC.

  2. 2

    Verify that the pink (PNK) wire has ground with the key on but engine off.

    Connect the black multimeter test lead (using the appropriate tool) to the PNK wire. Connect the red multimeter test lead to the positive battery terminal.

    Your multimeter should read 10 to 12 Volts DC.

Let's take a look at your test results:

CASE 1: Your multimeter confirms that the heater is getting power and ground- This is the correct and expected test result.

For our last test, we need to verify that your 1.6L Suzuki Sidekick's O2 sensor heater's resistance is within specification. For this test, go to TEST 2: Testing the Heater Element's Resistance.

CASE 2: Your multimeter confirms that the heater IS NOT getting power and ground- The most likely cause is that power is missing due to a blown fuse or a short (or open) in the wiring. You'll need to check fuse #16 (10 amps) in the fuse box and make sure it's not blown.

If the fuse is OK, your next step is to find out why this battery power is missing using a wiring diagram.