Disclaimer: The following is provided as a GUIDE ONLY, and neither myself nor Ozhonda take any responsibility for the outcomes of someone else doing the following. You follow these steps at your own risk!
No part of this DIY is to be reproduced with out acknowledgment of the site and author it came from, ie me and ozhonda.com. Do not rip parts off and claim them as your own.
SO2 "Secondary Oxygen Sensor". The SO2 is commonly located on the exhaust pipe after the cat or on the exhaust manifold. The SO2 monitors exhaust gasses and provides the ECU with a voltage relevant to fuel mixture from rich 0.8v to lean 0.2v, target voltage for optimum combustion is 0.4v called lambda. Hondas have three varieties for O2 sensors. Commonly used on OBDO and SOHC OBDI cars is the single wire O2, and on OBDI DOHC ( mainly VTiR ) 4 wire 02. The extra wires are for a built in heater in the sensor to assist getting the sensor to a working temp.
Aim:
Diagnose code 2.
Required:
Basic Testing
- Digital Multi Meter
- paper clip
- waveform viewer or an O2 monitor Kit from Jaycar
Symptoms
A faulty SO2 will trigger code 2. The Engine light will come on and code 2 will be registered in ECU memory. An open circuit in the SO2 is a common cause for code 2. Also a worn out sensor will trigger this code. The engine will run rich as the O2 sensor can only register a lean reading when its on its way out. Ensure you only use sensor safe sealant on engine to gasket surface areas as silicone based sealants will destroy the O2 sensor. The Secondary sensor must never be plugged into the primary sensor location on the exhaust manifolds that have two O2 sensors and the Primary monitors cyl 1 and 4 and the secondary monitors 2 and 3. So if you have them in back to front the ECU will monitor the primary O2 and trim the wrong set of injectors for fuel mixture causing the engine to run pretty bad.
Basic Test
- Perform a Visual inspection and make sure the SO2 is Connected.
4 wire PO2 Pinout Picture
wire side of connector back probing
Single wire SO2
wire side of connector back probing
**** Continuity Test ****
Set your multi meter to continuity. This setting is mostly a picture if a sound .))) when you touch the Red and Black leads together on your meter it should beep.
STEP 1
make sure the Ignition is off and unplug the SO2 Connector and the ECU Connectors for this test
Continuity test between SO2 Pin 1 and ECU, Connect your Red multi meter lead on the SO2 Pin 1, Back probe* the Black multi meter lead on the ECU Pin bellow that suits your car.
OBDO = C8
OBDIIa = D14
OBDIIb = A23
your multi meter should beep and read short or 000.0ohms. Place the black multi meter lead on a good ground source. You should not get beeping, this is testing for short to ground.
**** Voltage Test ****
Step 1
Check the SO2 for its signal Voltage. Connect the O2 Tester to the battery for power and the signal wire to the O2 signal wire. ( see above pic for 4wire O2 )
KOER* with warm engine.
At Idle the LED's should flash from lean to rich back to lean to rich in a reasonable time frame ( like in the below picture ). This indicates the O2 sensor is operational and the Engine is in closed loop.
If you flip the throttle, the Sensor should read rich and as you back off the throttle it should drop down to lean for about 4 seconds ( as the injectors cut out ). see bellow picture
If the O2 is faulty, then you will get a lazy type of reading like in the pic bellow, or even no signal at all.
Replace the O2 Sensor if its lazy or non responsive.
* Notes
KOEO = Key On Engine Off
KOER = Key On Engine Running
Back probe the sensor, use a paperclip and push it into the connector then touch/clip your multi meter lead to the paper clip
No part of this DIY is to be reproduced with out acknowledgment of the site and author it came from, ie me and ozhonda.com. Do not rip parts off and claim them as your own.
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