P0141

HEATING REAR HEATED OXYGEN SENSOR





Symptom Of Fault.
The CHECK ENGINE lamp (MIL) is on.

Conditions.
^ Heating circuit active.
^ Heating circuit current below 500 mA or above 2300 mA for 5 seconds.

NOTE: Oxygen sensor heating is activated at engine coolant temperatures above 50°C (122°F).

Diagnostic Help.
The oxygen sensor's heating circuit current can be ascertained using an ISAT scan tool.
- Select "READ FUNCTIONS".
- Select "02S 2 PREHEATING"
With the engine hot, the ISAT scan tool should show a heating current of 700-1000 mA. Oxygen sensor heating can be activated by means of the ISAT scan tool.
- Select "ACTIVATE".
- Select "02S 2".

If diagnostic trouble codes P0135 and P0141 are present, the cause of the fault is:
- because fuse 28 has blown
- the common power supply for the oxygen sensors from fuse 28 is absent





Diagnostic Procedure.
1. Check additional diagnostic trouble codes in the Trionic system.
- Obtain readouts of all diagnostic trouble codes using the ISAT scan tool.

Are P0135 and P0141 present?
YES:
^ Continue with point 2.
NO:
^ Continue with point 3.

2. Check the oxygen sensors' heating circuit resistance

The engine should have been switched off for at least 5 minutes.
- Check fuse 28 and change it if necessary.
- Unplug the 4-pin connectors of both oxygen sensors.
- Check the resistance of both sensors:
pins 1-2: 1.8-4.0 ohms.

Are the resistance readings OK?
YES:
^ Repair or replace the leads between pin 1 of the connectors of both oxygen sensors and fuse 28. Then continue with point 4.
NO:
^ Change the relevant oxygen sensor and proceed to point 4.





3. Check the heating circuit ground connection and power supply
- Unplug the oxygen sensor's 4-pin connector.
- Start the engine and run it at idling speed until the coolant temperature is above 50°C (122°F).
- Connect the test lamp to:
^ pin 1 and B-
^ B+ and pin 2

Does the test lamp light up in both cases?
YES:
^ Change the sensor and continue with point 4.
NO:
^ Rectify the lead in question and proceed to point 4.





4. Final check:
- Clear the diagnostic trouble code.
- Implementation of driving cycle: Drive the car at varying loads and engine rpm for 5 minutes.
- Evaluation of driving cycle: Check whether the diagnostic trouble code has recurred.

Has the diagnostic trouble code recurred?
YES:
^ Proceed at "Before Replacing a Control Module". Component Tests and General Diagnostics
NO:
^ The remedial measure taken was correct.