O2 Sensor - CEL - Code P0137

[1schoir]

CEL went on and has been cleared, but keeps returning.

I plugged in my Durametric unit and got the following code:

P0137 Factory Fault Code 12

Oxygen Sensor ahead of Catalytic Converter (Cylinders 1-3) Short Circuit.

I don't know if "Short Circuit" means bad O2 sensor or if one of the wires leading to it is shorted out.

I did go under the car, disconnected the plug leading to the subject O2 sensor, cleaned the connections and reconnected the plug but it still throws the same code. No evidence of any frayed wires.

I am not sure if there is any connection, but the CEL may have come on shortly after I had an overflow of coolant into the trunk, as I know it is the same general area below which the O2 sensors on the psgr side are located.

Car is a 986 MY '97 with 16K miles on it. (Long story).

Any thoughts appreciated.

Regards, 1schoir. :(

[Loren]

P0137 Oxygen Sensor After Catalytic Converter (Cylinders 1 - 3) - Signal Wire Short Circuit to Ground or Incorrect Voltage

Potential causes:

Short circuit in signal wire to ECM ground

DME control module output stage short to ground

Fault area:

- Wiring harness or housing ground.

- Oxygen sensor

- DME control module or housing ground.

Troubling shooting:

Check and repair wiring harness.

Replace O2 sensor.

Wiring harness testing

1. Remove all four O2 connectors.

2. Switch on the ignition.

3. Connect voltmeter at sleeve to pins 3 and 4 of O2 connector 1 after catalytic converter.

Display: approx. 450 mV

4. Connect voltmeter at sleeve to pin 3 and ground.

Display: approx. 720 mV

If the measurement according to items 3 and 4 does not show the specified values, remove DME control module connector and check wiring for short to ground.

If no short to ground can be detected, replace DME control module.

Sensor testing:

1. Remove O2S connector 1 after catalytic converter.

2. Connect ohmmeter on pin side to pin 3 and to O2 housing.

Display: infinite ohms

3. Connect ohmmeter on pin side to pin 4 and to O2 housing.

Display: infinite ohms

4. Connect ohmmeter on pin side to pins 4 and 2.

Display: infinite ohms

5. Connect ohmmeter on pin side to pins 3 and 2.

Display: infinite ohms

If any test fails replace the O2 sensor(s) that failed.

[1schoir]

P0137 Oxygen Sensor After Catalytic Converter (Cylinders 1 - 3) - Signal Wire Short Circuit to Ground or Incorrect Voltage

Potential causes:

Short circuit in signal wire to ECM ground

DME control module output stage short to ground

Fault area:

- Wiring harness or housing ground.

- Oxygen sensor

- DME control module or housing ground.

Troubling shooting:

Check and repair wiring harness.

Replace O2 sensor.

Wiring harness testing

1. Remove all four O2 connectors.

2. Switch on the ignition.

3. Connect voltmeter at sleeve to pins 3 and 4 of O2 connector 1 after catalytic converter.

Display: approx. 450 mV

4. Connect voltmeter at sleeve to pin 3 and ground.

Display: approx. 720 mV

If the measurement according to items 3 and 4 does not show the specified values, remove DME control module connector and check wiring for short to ground.

If no short to ground can be detected, replace DME control module.

Sensor testing:

1. Remove O2S connector 1 after catalytic converter.

2. Connect ohmmeter on pin side to pin 3 and to O2 housing.

Display: infinite ohms

3. Connect ohmmeter on pin side to pin 4 and to O2 housing.

Display: infinite ohms

4. Connect ohmmeter on pin side to pins 4 and 2.

Display: infinite ohms

5. Connect ohmmeter on pin side to pins 3 and 2.

Display: infinite ohms

If any test fails replace the O2 sensor(s) that failed.

Thanks for detailing procedure, Loren.

The Durametric says "Oxygen Sensor AHEAD of Catalytic Converter" for Factory Code P0137. Does that code refer to the O2 sensors both AHEAD of and AFTER the catalytic converter?

Regards, 1schoir.

[Loren]

My information came from the Porsche OBD II 5.2.2 Service Manual (a 1997 Boxster would be DME 5.2.2).

[1schoir]

My information came from the Porsche OBD II 5.2.2 Service Manual (a 1997 Boxster would be DME 5.2.2).

Yes, the Durametric identifies the 1997 Boxster as "Motronic 5.2.2 (Engine DME)".

Guess I will try the procedures you outlined on both of the O2 Sensors, i.e., the one AHEAD OF and the one AFTER the catalytic converter on the psgr side.

Thanks again.

Regards, 1schoir.

[McCullough]

My information came from the Porsche OBD II 5.2.2 Service Manual (a 1997 Boxster would be DME 5.2.2).

Where does one acquire the mentioned "Porsche OBD II 5.2.2 Service Manual?"

--- Tom

[1schoir]

P0137 Oxygen Sensor After Catalytic Converter (Cylinders 1 - 3) - Signal Wire Short Circuit to Ground or Incorrect Voltage

Potential causes:

Short circuit in signal wire to ECM ground

DME control module output stage short to ground

Fault area:

- Wiring harness or housing ground.

- Oxygen sensor

- DME control module or housing ground.

Troubling shooting:

Check and repair wiring harness.

Replace O2 sensor.

Wiring harness testing

1. Remove all four O2 connectors.

2. Switch on the ignition.

3. Connect voltmeter at sleeve to pins 3 and 4 of O2 connector 1 after catalytic converter.

Display: approx. 450 mV

4. Connect voltmeter at sleeve to pin 3 and ground.

Display: approx. 720 mV

If the measurement according to items 3 and 4 does not show the specified values, remove DME control module connector and check wiring for short to ground.

If no short to ground can be detected, replace DME control module.

Sensor testing:

1. Remove O2S connector 1 after catalytic converter.

2. Connect ohmmeter on pin side to pin 3 and to O2 housing.

Display: infinite ohms

3. Connect ohmmeter on pin side to pin 4 and to O2 housing.

Display: infinite ohms

4. Connect ohmmeter on pin side to pins 4 and 2.

Display: infinite ohms

5. Connect ohmmeter on pin side to pins 3 and 2.

Display: infinite ohms

If any test fails replace the O2 sensor(s) that failed.

UPDATE:

Tested wiring harness as per procedure above, got correct voltage readings.

Did not test, but replaced 02 Sensor AFTER catalytic converter on psgr side (cylinder bank 1-3). (Bought Bosch Part #13806, about $150).

Cleared CEL and it has not come back on since. Now about 75 miles.

So, it would appear that the Durametric readout is incorrect when it points to 02 Sensor BEFORE catalytic converter.

Thanks, Loren.

Regards, 1schoir.