P0135

DIAGNOSTIC TROUBLE CODE P0135
Oxygen sensor preheating, malfunctioning or not working at all

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

Conditions.
The preheating current is less than 500 mA or more than 2300 mA for 5 seconds.

DIAGNOSTIC PROCEDURE

1. Checking The Fuse
Check fuse 28.

2. Checking The Preheating Circuit
Connect the Scan Tool.
Start the engine and run it at idling speed.
Select "READ FUNCTIONS".
Select "OXY SENSOR PREHEAT".

The Scan Tool shows the prevailing current consumption of the oxygen sensor preheating circuit.

Nominal current consumption with the engine warmed up is 700-1000 mA.

If the reading is OK, continue with point 7.

If the reading is not OK, continue with point 3.






3. Checking The Electrical Interfaces Of The Preheating Circuit
Switch off the engine.
Unplug the oxygen sensor's 4-pin connector.

Connect a test lamp to pins 1 and 2 of the oxygen sensor connector.

Ignition switch in the ON position.
Select "ACTIVATE".
Select "OXY SENSOR PREHEAT".

Preheating is now activated for 10 seconds. For longer activation the command must be repeated.

The test lamp should light up throughout the activation time.

If the lamp lights up, change the oxygen sensor.

If the test lamp does not light up, continue with point 4.

4. Checking The Current Consumption Of The Preheating Circuit
Start the engine and run it at idling speed.

Take a voltage reading at the oxygen sensor connector as follows:
- Between battery positive and pin 1 about 12 V
- between pin 2 and battery negative about 12 V.

If no voltage is present on pin 1, continue with point 6.

If voltage is present on pin 2, continue with point 5.






5. Checking The Circuit
Check the circuit between pin 2 of the oxygen sensor connector and pin 87 of the fuel pump relay for continuity.

If the circuit is OK, continue with point 7

If the circuit is not OK, rectify the fault.

6. Checking The Wiring
Check the lead between pin 1 of the oxygen sensor connector and pin 50 of the control module for discontinuity and shorting.


If the lead is OK, continue with point 7

If the lead is not OK, rectify the fault.

7. Final Check
Clear the diagnostic trouble code, drive the car on test and check whether the trouble code is generated afresh.

If the DTC is generated again, refer to Before Replacing A Control Module.

If the DTC is not generated again, the action taken to rectify the fault was correct, otherwise the fault is of intermittent nature.