Oxygen Sensor Heater Test -P0155 (1999-2000 2.5L Grand Vitara)

If the check engine light on your 2.5L Grand Vitara is lit by a diagnostic trouble code (DTC) P0155: Heated Oxygen Sensor Circuit Malfunction Bank 2 Sensor 1, this tutorial will help you diagnose it.

You don't need any expensive diagnostic test equipment to test the front right oxygen sensor's heater... all you'll need is a multimeter. I'll show you the 3 basic tests you'll need to perform to find out if the O2 sensor is bad or not.

NOTE: This oxygen sensor is known by several different names:

  1. Upstream Heated Oxygen (O2) Sensor 2.
  2. HO2S Sensor 2.
  3. Oxygen Sensor Bank 2 Sensor 1.
  4. Front Right Oxygen Sensor.

Here are the contents of this tutorial:

  1. Circuit Descriptions of Bank 2 Sensor 1 Oxygen Sensor.
  2. TEST 1: Verifying The Heater Element Is Getting Power.
  3. TEST 2: Verifying The Heater Element Is Getting Ground.
  4. TEST 3: Testing The Heater Element's Resistance.
  5. Oxygen Sensor Locations (1999-2000 2.5L Grand Vitara ).
  6. Where To Buy The Oxygen Sensor and Save Some $$$.
  7. More 2.5L Suzuki Diagnostic Tutorials.

NOTE: To test a P0135: Heated Oxygen Sensor Circuit Malfunction Bank 1 Sensor 1 trouble code, take a look at this tutorial: Oxygen Sensor Heater Test -P0135 (1999-2000 2.5L Grand Vitara).

Circuit Descriptions of Bank 2 Sensor 1 Oxygen Sensor

Oxygen Sensor Heater Test -P0155 (1999-2000 2.5L Grand Vitara)

The Bank 2 Sensor 1 oxygen sensor has a total of 4 wires sticking out of it. 2 of the 4 wires feed power and ground to its heater element. The other 2 are for the oxygen sensing part of the sensor.

Below I've included a brief description of the O2 sensor's wires. We'll be needing this info to troubleshoot code P0155 in tests 1, 2 and 3 of this tutorial:

NOTE: You can find the location of the O2 sensors on your 2.5L Suzuki: 1999-2000 2.5L Grand Vitara Oxygen Sensor Locations.

Bank 2 Sensor 1 Oxygen Sensor Pinout
(1999-2000 2.5L Grand Vitara)
Pin Wire Color Description
1 GRY/YEL O2 Signal Ground
2 RED/BLU O2 Signal
3 BLK/RED Heater Ground (-)
4 BLU Heater Power (+)

TEST 1: Verifying The Heater Element Is Getting Power

Oxygen Sensor Heater Test -P0155 (1999-2000 2.5L Grand Vitara)

The heater element inside the front right oxygen sensor (HO2S 2/1) needs battery power and ground to heat up.

So, to get our P0155 DTC diagnostic under way, in this first test section we're gonna' make sure the right front O2 sensor's getting power (in TEST 2 we'll check for ground).

CAUTION: Do all oxygen sensor tests with a completely cold engine! The O2 sensor and the exhaust manifold it's bolted into can get and stay extremely hot long after the engine has been shut down! Be careful and take all necessary safety precautions! If you raise your vehicle with a jack, place it on jack stands!

IMPORTANT: The pinout in the illustration above is of the connector on the oxygen sensor itself. To check for power, you need to test the BLU wire of the engine wiring harness sensor connector.

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

  1. 1

    Locate the Bank 2 Sensor 1 oxygen sensor and disconnect it from its engine wiring harness connector.

  2. 2

    Locate the BLU wire of the engine wiring harness oxygen sensor connector.

  3. 3

    With your multimeter in Volts DC mode, probe the BLU with the red multimeter lead.

    Ground the black multimeter lead directly on the battery's negative terminal. (if you don't have a multimeter or need to upgrade your's take a look at my recommendation here: Buying A Digital Multimeter For Automotive Diagnostic Testing).

  4. 4

    With the Key On Engine Off (KOEO), the BLU wire should have 10 to 12 Volts DC.

Let's take a look at your test results:

CASE 1: Your multimeter shows that the BLU wire is feeding 10 to 12 Volts DC to HO2S 11- Good, since this confirms that the oxygen sensor's heater element is getting power.

The next step is to make check that the black (BLK/RED) wire, of the O2 sensor engine wiring harness connector, is feeding ground to the heater element. For this test, go to TEST 2: Verifying The Heater Element Is Getting Ground.

CASE 2: Your multimeter shows that the BLU wire IS NOT feeding 10 to 12 Volts DC to HO2S 11- Re-check that you're testing the correct wire and that the Key is in the RUN position (but don't crank or start the engine) and re-test.

If you still don't see 10 to 12 Volts DC... then this test result tells you that the Bank 2 Sensor 1 oxygen sensor itself IS NOT BAD... since without power, the heater element within it won't work.

Although it's beyond the scope of this article... the next step is to find out why this battery power is missing using a wiring diagram.