P0135

DTC P0135:

DIAGNOSTIC TROUBLE CODE PO135
PREHEATING OF HEATED OXYGEN SENSOR, MALFUNCTIONING OR NOT WORKING AT ALL

Fault symptom
The malfunction indicator lamp is on.

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

Diagnostic procedure
1. Check fuse 38.

2. Connect an ISAT scan tool.

- Start the engine and run it at idling speed.

The prevailing current consumption for the oxygen sensor's preheating circuit is shown on the ISAT menu "READ FUNCTIONS" and with the "PREHEAT OXY SENSOR" command.

The nominal value when the engine is warmed up is 700-1000 mA.

- If the measured value is correct, continue with step 6.
- If the measured value is incorrect, continue with step 3.

DTC P0135:

3. Switch OFF the engine.

- Unplug the 4-pole connector of the oxygen sensor.
- Connect the test lamp between the oxygen sensor's connector (female), pin 2 to pin 1.
- Ignition switched ON.
- Select the "PREHEAT OXY SENSOR" command on the "ACTIVATE" menu.

Preheating is now activated for 10 seconds. If you want a longer activation time, repeat the command. During the activation time, the test lamp lights up with a steady glow.

- If the test lamp comes on, install a new oxygen sensor.
- If the test lamp does not come on, continue with step 4.

4. Start the engine and run it at idling speed.

- Measure the voltage in the oxygen sensor's connector (female).
^ Batt + to pin 1 ______ approx. 12 V.
^ Pin 2 to Batt - ______ approx. 12 V.
- If there is no voltage on pin 2, continue with step 5.
- If there is no voltage on pin 1, continue with step 6.

DTC P0135:

5. Check the continuity of the circuit between pin 2 of the oxygen sensor's connector and pin 87 of the fuel pump relay.

6. Check the lead between pin 1 on the oxygen sensor's connector and pin 50 on the ECM for discontinuity and shorting.

7. Erase the diagnostic trouble code and drive the car to see whether the DTC is generated again.

- If the diagnostic trouble code is registered, continue at "Procedure before replacing ECM".
- If the diagnostic trouble code is not registered, the action taken is correct. Otherwise the fault is intermittent in nature.