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Troublecode OBDII (ALPHA) P CODE

Troubleshooting P1131
Lack Of HO2S Switch - Sensor Indicates Lean.

thia code after changing back O2 Sensor.
help out. if you can please.

P1131 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1


If the rear upstream sensor has been replaced and you still get this code, either the wiring is bad or air is entering the the rear bank. Check the connector and wires to the sensor. If engine performance is affected this could be at the intake gaskets, and if not, at the exhaust gaskets or EGR tube connection.

thanks can you please explain what you mean by air is entering the the rear bank. could there be a leak in the os2 sensor bolt in.

i had the same code p1131, mine was the upper intake gasket leaking. Installed new ones and code was gone.

that means i have to take off the upper intake manifold.