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Troubleshoot the P0135 Posted by sam96CS [Email] ![]() ![]() In Reply to: Reaches operating temperature in < 3 minutes, JerseySaab ![]() |
There are 4 possibilities:
1. The P0125 and the P0135 are both correct.
2. The P0125 and the P0135 are both bogus.
3. The P0125 is bogus and the P0135 is correct.
4. The P0125 is correct and the P0135 is bogus.
Obd2 is a gold mine for car part retailers and for mechanics who would rather replace parts than diagnose.
It won't hurt anything to set aside the P0125 troubleshooting and move on the troubleshooting the P0135, in which the ECU claims that a fault exists in the front O2 sensor's heating circuit.
The conditions that causes a P0135:
1. The front O2 sensor's heating circuit is turned on.
2. For a 5 second interval the heating circuit's current is either below 500 mA or above 2300 mA.
(note: O2 sensor heating is activated when the coolant temperature is above 122 degrees F. The normal heating current is 700-1000 mA.)
Caution: in the test below the ohm meter should be connected to the O2 sensor's connector pins, not to the connector wiring that leads to the ECU.
Pins 1 and 2 of the front O2 sensor are the heating circuit. You can test the resistance at the 4-pin connector after the engine has been switched off for at least 5 minutes. The resistance should be between 1.8 and 4.0 ohms.
If you have a test lamp then there is a way to check the ground connection and power supply to the sensor's heating circuit. I can post instructions from the Trionic obd2 manual if you need them.
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