P0136

REAR HEATED OXYGEN SENSOR, CYL BANK 1 (REAR BANK)





Fault Symptoms.
CHECK ENGINE lamp (MIL) on.
Any other diagnostic trouble codes, such as misfiring and adaptation.

Conditions.
For all diagnostic trouble codes, preheating shall have been active for more than 200 seconds after starting and the closed loop system should be active.

P0136
^ Sensor voltage between -0.04 V and 0.04 V for longer than 225 seconds.

P0137
^ Sensor voltage -0.15 V for longer than 0.2 seconds.

P0138
^ Sensor voltage higher than 1.1 V for longer than 0.2 seconds.

P0139
^ Sensor voltage low in spite of maximum closed loop enrichment.
^ Sensor voltage high in spite of maximum closed loop weakening.

P0140
^ Sensor voltage 0.4 - 0.5 V for longer than 11 minutes.





Diagnostic Help.
The performance of the oxygen sensor can be ascertained with an ISAT scan tool.
- Select "READ FUNCTIONS"
- Select "OXY SENSOR BANK 1
- Read "OXYGEN SENSOR 2"

At full load the ISAT scan tool should show a reading higher than 0.7 V.

At fuel shut-off the ISAT scan tool should show a reading of about 0 V.

NOTE:
If the reference ground or voltage of any of the oxygen sensors is shorted to battery positive (B+) in the wiring harness or in any of the oxygen sensors, all the following diagnostic trouble codes will usually be generated: P0132, P0152, P0138 and P0158.

If the reference ground of the oxygen sensors via pin 46 is shorted to battery negative (B-) in the wiring harness or in any of the oxygen sensors, all the following diagnostic trouble codes will usually be generated: P0131, P0151, P0137 and P0157.

If the preheating element of an oxygen sensor develops a fault the performance of the sensor will deteriorate, particularly at idling speed. A diagnostic trouble code indicating an open circuit in the sensor could then be generated. If diagnostic trouble codes for open circuit and preheating are both generated, the trouble code for preheating should be attended to first. Following this, the operation of the oxygen sensor should be checked.

Check The Wiring.
Intermittent faults may occur as a result of temporary. short circuits and breaks in the wiring. jiggle the wiring at several points and in different directions to ascertain whether the wiring harness, including any connectors, is causing the trouble. Observe the multimeter, ISAT scan tool or test lamp while doing this.





Diagnostic Procedure.
1. Check other diagnostic trouble codes in the Motronic system
- Use an ISAT scan tool to obtain readouts of all diagnostic trouble codes.

Any other diagnostic trouble codes?
YES: Continue with point 2.
NO: Continue with point 7.

2. Check other diagnostic trouble codes in the Motronic system

Does the ISAT scan tool show diagnostic trouble code P1117?
YES: Carry out fault diagnosis and a final check as described for diagnostic trouble code P1117.
NO: Continue with point 3.

3. Check other diagnostic trouble codes in the Motronic system,

Does the ISAT scan tool show P0138 and any of the following diagnostic trouble codes: P0132, P0152 or P0158?
YES: Continue with point 5.
NO: Continue with point 4.

4. Check other diagnostic trouble codes in the Motronic system

Does the ISAT scan tool show P0137 and any of the following diagnostic trouble codes: P0131, P0151 or P0157?
YES: Continue with point 6.
NO: Continue with point 7.





5. Check shorting to battery positive (B+)

One of the leads of the oxygen sensors connected to pin 18, 19, 76, 77 or 46 is shorted to battery positive (B+) in the wiring harness or in one of the oxygen sensors.
- Check the insulation of the oxygen sensors.
- Unplug the four 4-pin oxygen sensor connectors.
- Check the resistance of the sensors:
^ pins 1-3: OL(infinite resistance)
^ pins 1-4: OL(infinite resistance)

Are all resistance readings OK?
YES: Check the lead in question connected to control module pin 18, 19, 76, 77 or 46 and repair or replace it if necessary. Then continue with point 9.
NO: Change the oxygen sensor in question. Then continue with point 9.

6. Check shorting to battery negative (B-)

The lead connected to pin 46 of the control module is shorted to battery negative (B-) in the wiring harness or in one of the oxygen sensors.
- Check the insulation of the oxygen sensors.
- Unplug the four 4-pin oxygen sensor connectors.
- Check the resistance of the sensors:
^ pin3 to B: OL
^ pin4 to B: OL

Are all resistance readings OK?

YES: Check the lead connected to pin 46 of the control module for shorting to ground and repair or replace it if necessary. Then continue with point 9.
NO: Change the oxygen sensor in question. Then continue with point 9.





7. Check the control module's sensor ground
- Unplug the 4-pin sensor connectors.
- Turn the ignition switch to the ON position.
- Take a voltage reading on the relevant connector.
^ pin3 to B: 0.7 V.

Is the reading obtained OK?
YES: Continue with point 8.
NO: Check the lead in question and repair or replace it if necessary. Then continue with point 9.

8. Check the control module's sensor input
- Connect the ISAT Scan Tool.
- Turn the ignition switch to the ON position.
- Select "READ FUNCTIONS".
- Select "OXYGEN SENSOR BANK 1"
- Read "OXYGEN SENSOR 2"

The ISAT scan tool should show a reading of about 0.45 V. Connect a jumper lead between pins 3 and 4 in the oxygen sensor connector.

The ISAT scan tool should show a reading of about 0.00 V.

Are all readings OK?
YES: Change the oxygen sensor. Then continue with point 9.
NO: Check the leads in question and repair or replace them as necessary. Then continue with point 9.





9. Final check
- Clear the diagnostic trouble code.
- Implementation of driving cycle:
^ Drive the car at varying engine loads and rpm for 5 minutes.
- Evaluation of driving cycle:
^ Connect the ISAT Scan Tool.
^ Select "ON / OFF".
^ Select "DIAGNOSTIC STATUS".
^ Select "OXY SENSOR BANK 1".
^ Read "OXYGEN SENSOR 2"

Does the ISAT scan tool read "NOT READY"?
YES: Repeat the driving cycle.
NO: Check whether the diagnostic trouble code has recurred.

If the diagnostic trouble code has recurred: Continue at "Before Replacing a Control Module". Component Tests and General Diagnostics

If the diagnostic trouble code has not recurred: The steps taken to rectify the fault were correct.