DIY PGMFI Diagnostics - Code 42 SO2H

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.




SO2H "Secondary Oxygen Sensor Heater". The SO2H is commonly located on the back of the exhaust pipe under the car after the cat. Most Commonly the SO2H is the 2nd Oxygen sensor on a V6 car. The SO2H helps heat up the Oxygen Sensor to operating temp at start up to get the O2 sensor working sooner. The Heater is a wire wound heater element.




Aim:

Diagnose code 42.

http://ecu-man.com/diy/pgmfi/mil/pgmfi-code-42.gif



Required:

Basic Testing

- Digital Multi Meter
- paper clip




Symptoms

A faulty SO2H will trigger code 42. The Engine light will come on and code 42 will be registered in ECU memory. An open circuit in the SO2H is a common cause for code 42.


Basic Test


- Perform a Visual inspection and make sure the SO2H is Connected.


PO2H Pin out Picture




http://ecu-man.com/diy/pgmfi/ho2/PGMFI-Ho2-conn.JPG


wire side of connector back probing


HO2 wire colour

1 = wht
2 = grn or gry
3 = blk
4 = blk




**** Voltage Test ****



Set your multi meter to DC Volts ( 20v scale )


Step 1 ( Reference Voltage test )



Check the SO2H for its Reference Voltage from the ECU. Connect the Black Lead from your multi meter to the chassis for a good ground. Back probe* the SO2H with the Red lead to Pin 3 of the SO2H while the sensor is connected.

KOER* you must get 12v

If you get 12v proceed to step 2,

if you do not get 12v, repair open or short circuit to ECU from Pin 3 of SO2H to the bellow ECU Pin ( also see continuity test bellow )

OBDIIa = A11
OBDIIb = B1


If you do not get 12v from the ECU pin above, replace the ECU.





STEP 2


Check the SO2H Signal. Connect the Red Lead from your multi meter to the battery Positive terminal. Back probe* the SO2H with the black lead to Pin 4 of the SO2H while the sensor is connected.

KOER* you should get 12v.


also check the SO2H signal at the ECU end at the following pin bellow


OBDIIa = A6
OBDIIb = A8


If You do not get 12v replace the ECU



***** Its is always best to check sensor outputs at the sensor side *****




**** 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 SO2H Connector and the ECU Connectors for this test



Continuity test between SO2H Pin 3 and ECU, Connect your Red multi meter lead on the SO2H Pin 3, Back probe* the Black multi meter lead on the ECU Pin bellow that suits your car.




OBDIIa = A11
OBDIIb = B1


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.





STEP 2

make sure the Ignition is off and unplug the SO2H Connector and the ECU Connectors for this test

Continuity test between SO2H Pin 4 and ECU, Connect your Red multi meter lead on the SO2H Pin 4, Back probe* the Black multi meter lead on the ECU Pin bellow that suits your car.


OBDIIa = A6
OBDIIb = A8


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.


If any of your continuity tests fail between the SO2H and ECU, repair the OPEN in the wire between the SO2H and ECU that failed.

If any of your continuity tests fail between the SO2H and ground, Find the short circuit and repair it. look for squashed wires, or for damage to any part of the PGMFI loom.





**** Resistance Test **** Set the multi meter to ohms ( 1K scale )


Unplug the SO2H, connect your Red multi meter lead to Pin 3 of the SO2H. Connect your Black multi meter lead to Pin 4 of the SO2H.



the resistance should be between 10 to 40 ohms



reset the ECU and road test the car.






* 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



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!