How To Test Trouble Code P0135 (2001-2003 Honda 1.7L)

TEST 2: Verifying The Heater Element Is Getting Ground

The BLK/WHT wire, of the upstream O2 sensor harness connector, is the one that supplies the heater element with Ground.

To test this Ground circuit, we'll do a simple multimeter voltage test.

IMPORTANT: The Ground supplied by the BLK/WHT wire is provided directly by your Honda Civic's PCM. Be careful and don't accidentally or intentionally short this wire to battery power, or you'll fry the PCM.

These are the test steps:

1. 1

   Locate the BLK/WHT wire of the O2 sensor's harness connector.
   
   NOTE: Remember, you'll test the wire that's on the engine wiring harness connector side and NOT on the O2 sensor itself.

2. 2

   Place your multimeter in Volts DC mode and:

   1. Connect the red multimeter test lead to battery (+).
   2. Probe the BLK/WHT wire of the O2 sensor's harness connector.
3. 3

   With the Key On Engine Off, this wire should have 10 to 12 Volts DC.

Let's take a look at your test results:

CASE 1: The multimeter registered 10 to 12 Volts DC. This test result lets you know that your 1.7L Honda Civic's upstream oxygen sensor's heater element is getting Ground.

So far you've confirmed that the upstream O2 sensor's heater element is getting both power and Ground. The next step is to check the heater element's resistance with your multimeter...for this test, go to: TEST 3: Testing The Heater Element's Resistance.

CASE 2: The multimeter DID NOT register 10 to 12 Volts DC. Re-check all of your connections and make sure you're testing the correct terminal.

If your multimeter still doesn't register the 10 to 12 Volts DC, then the most likely cause of this missing Ground is an ‘open’ in the BLK/WHT wire between your Honda Civic's PCM harness connector and the O2 sensor's harness connector.

TEST 3: Testing The Heater Element's Resistance

Since you have checked and confirmed that the upstream oxygen sensor on your Honda Civic is getting both juice and Ground, the next (and last) step is to check the heater's internal resistance.

This is another multimeter test but with it in Ohms (Ω) mode and it applies to both the D17A1 and D17A2 upstream oxygen sensor.

NOTE: Just a reminder that the upstream oxygen sensor has to be completely cold before proceeding with this test since the manual calls for the O2 sensor to be at room temperature for the resistance test.

OK, this is what you need to do:

1. 1

   Locate the O2 sensor terminals number 3 and number 4 of the O2 sensor connector itself (not the engine wiring harness O2 connector).

2. 2

   With your multimeter in Ohms mode, probe terminals number 3 and number 4 of the O2 sensor itself.
   
   NOTE: The upstream O2 sensor for the D17A2 engine has female metal terminals. Avoid probing the front of these female terminals with the multimeter test leads or you run the risk of damaging them.

3. 3

   If all is OK, you should see about 3 to 3.6 Ωs on your multimeter.
   
   If the heater element is fried, your multimeter will show an open (usually indicated by the letters OL) or a number over 10 K Ωs.

Let's take a look at your test results:

CASE 1: Your multimeter confirmed the indicated resistance. This test result tells you that your 1.7L Honda Civic's pre-catalytic converter oxygen (O2) sensor's heater is OK.

CASE 2: Your multimeter showed an open circuit (OL). This confirms that the upstream (Bank 1 Sensor 1) O2 sensor's heater element is fried. Replacing the upstream O2 sensor with a new one will solve the P0135 trouble code lighting up the check engine light (CEL).

Here are some more specifics: Since you have:

1. Confirmed that the upstream O2 sensor's heater element is getting power (TEST 1).
2.      -AND-
3. Confirmed that the upstream O2 sensor's heater element is getting Ground (TEST 2).
4.      -AND-
5. In this test you have confirmed that the heater element's resistance is out of specification.

... You can correctly conclude that the upstream O2 sensor on your 1.7L Honda Civic needs to be replaced with a new one.