A P0141: Secondary Heated Oxygen Sensor (Sensor 2) Heater Circuit Malfunction trouble code on your 1.7L equipped 2001-2005 Honda Civic (DX, EX, AND LX) indicates that the downstream O2 sensor's heater element is probably fried.
Fortunately, there's a very simple and easy way to find out if the downstream O2 sensor is bad (or not) and it involves 3 simple multimeter tests (no scan tool required).
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Verificar Código de Sensor de Oxígeno P0141 (2001-2003 Honda 1.7L) (at: autotecnico-online.com).
Circuit Descriptions Of The Upstream Oxygen Sensors
As you're already aware, there are 4 wires coming out your Honda Civic's downstream O2 sensor.
We're only gonna' worry about the two wires (circuits) that provide power and Ground to the heater element.
The other 2 are the ones that provide the oxygen content info of the exhaust, to the PCM (Powertrain Control Module = Fuel Injection Computer).
Here are the circuit descriptions of the 4 wires (taking into account the engine code):
|D17A1 Downstream Oxygen Sensor Pinout
(2001-2005 1.7L Honda Civic DX, LX)
|1||GRN/YEL||PHO2S (Sensor Signal)|
|2||WHT/RED||SG2 (Sensor Ground)|
|3||BLK/WHT||Heater Element Power|
|4||BLK/YEL||Heater Element Ground|
|D17A2 Downstream Oxygen Sensor Pinout
(2001-2005 1.7L Honda Civic EX)
|1||PNK||SG2 (Sensor Ground)|
|2||WHT/RED||PHO2S (Sensor Signal)|
|3||BLK/WHT||Heater Element Ground|
|4||BLK/ORG||Heater Element Power|
TEST 1: Verifying The Heater Element Is Getting Power
The first downstream O2 sensor test that we're gonna' do is to make sure that it's heater element is getting power.
If your Honda Civic is a DX or an LX model (D17A1 engine), the BLK/YEL wire of the downstream O2 sensor engine wiring harness connector is the one that provides this battery power.
If your Honda Civic is an EX model (D17A2 engine), the BLK/ORG wire of the downstream O2 sensor engine wiring harness connector is the one that provides this battery power.
IMPORTANT: The O2 sensor and the exhaust pipe can get and stay very hot! Perform this test with a completely cold engine. Be careful and take all necessary safety precautions!
OK, this is what you'll need to do:
Locate the downstream oxygen sensor and disconnect it from its harness connector.
Locate the BLK/YEL (or BLK/ORG) wire (depending on your specific Honda Civic model) of the downstream engine wiring harness oxygen sensor connector.
With your multimeter in Volts DC mode, probe the BLK/YEL (or BLK/ORG) with the red multimeter test lead.
Ground the black multimeter test lead directly on the battery negative (-) terminal.
With the Key On Engine Off (KOEO), this wire should have 10 to 12 Volts DC.
Let's take a look at your test results:
CASE 1: Your multimeter recorded 10 to 12 Volts DC. This voltage test result confirms that the heater element is receiving power.
The next step is to make check that the BLK/WHT wire, of the O2 sensor 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 DID NOT record the indicated voltage. 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 downstream oxygen (O2) sensor itself, on your 1.7L equipped Honda Civic IS NOT bad since without power, the heater element 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. On all models covered by this tutorial, the #4 10 amp fuse of the under-dash fuse/relay box is the one that provides power to this circuit and should be checked to make sure it's not blown.