P0135

Component Tests and General DiagnosticsHEATING, FRONT 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.

Diagnostic Help.
^ The oxygen sensor's heating circuit current can be ascertained using an ISAT scan tool.
- Select "READ FUNCTIONS".
- Select "02S 1 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 "O2S 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 PO135 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. 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.
- 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.