Troubleshooting a diagnostic trouble code (DTC) P0141: HO2S Heater Circuit Sensor 2 on your 2.2L Chevy Cavalier (Pontiac Sunfire) is a pretty easy affair.
You don't need any expensive diagnostic test equipment... all you'll need is a multimeter. I'll show you the 3 basic tests you'll need to perform to find out.
NOTE: This oxygen sensor is known by several different names:
- Downstream Heated Oxygen (O2) Sensor.
- HO2S Sensor 2.
- Rear Oxygen (O2) Sensor.
- Oxygen Sensor Bank 1 Sensor 2.
- Oxygen Sensor After the Catalytic Converter.
- Post-Catalytic Converter O2 Sensor.
Here are the contents of this tutorial:
- Circuit Descriptions Of The Downstream Oxygen Sensor.
- TEST 1: Verifying The Heater Element Is Getting Power.
- TEST 2: Verifying The Heater Element Is Getting Ground.
- TEST 3: Testing The Heater Element's Resistance.
- Where To Buy The Oxygen Sensor And Save Some $$$.
- More 2.2L GM Diagnostic Tutorials.
You can find this tutorial is Spanish here: Calentador del Sensor de Oxígeno -P0141 (1995-1998 2.2L Cavalier / Sunfire) (en: autotecnico-online.com).
Circuit Descriptions Of The Downstream Oxygen Sensor
The rear post-catalytic converter oxygen sensor on your 2.2L Cavalier (Sunfire) is a 4 wire sensor. This is due to the fact that two of those wires feed power and ground to an internal heater.
The other two wires are the ones that connect to the oxygen content monitoring (of the exhaust gas) part of the downstream O2 sensor.
Below, you'll find the color of the wires of the engine wiring harness oxygen sensor connector for the rear oxygen sensor:
|Downstream Oxygen Sensor Pinout (1995-1998 2.2L Cavalier / Sunfire)|
|A||TAN/WHT||O2 Signal Ground|
|C||BLK||Heater Ground (-)|
|D||BRN||Heater Power (+)|
TEST 1: Verifying The Heater Element Is Getting Power
The rear oxygen sensor gets power (12 Volts DC) from a fuse in the under-dash fuse block. These 12 Volts are then channeled to the rear O2 sensor thru' brown (BRN wire of the engine wiring harness oxygen sensor connector.
To check for these 12 Volts, we need to do a simple multimeter voltage test.
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 pinout in the illustration above is of the connector on the oxygen sensor itself. To check for power, you need to test the BRN wire of the engine wiring harness sensor connector.
OK, this is what you'll need to do:
Locate the downstream oxygen sensor and disconnect it from its harness connector.
Locate the BRN wire of the engine wiring harness oxygen sensor connector.
With your multimeter in Volts DC mode, probe the BRN with the red multimeter lead.
Ground the black multimeter lead directly on the battery's negative terminal.
With the Key On Engine Off (KOEO), the BRN wire should have 10 to 12 Volts DC.
Let's take a look at your test results:
CASE 1: The BRN wire has 10 to 12 Volts DC- Good, since this confirms that the rear oxygen sensor's heater element is getting power.
The next step is to make check that the black (BLK) 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: The BRN wire DOES NOT have 10 to 12 Volts DC- 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 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 using a wiring diagram.