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2002 Jetta 2.0L Engine Code P0036: Downstream O2 Sensor Heater Circuit Issue

Model: 2002 Jetta 2.0 Fault Code: P0036 Posted: 2015-05-20 16:50

My 2002 Jetta 2.0L vehicle is displaying Diagnostic Trouble Code (DTC) P0036 immediately after starting, and the code reappears repeatedly even after clearing it. The downstream oxygen sensor heater circuit is not receiving 12 volts — voltage readings at connector pins 1 and 2 show only 3.4V. I am wondering if there's a fuse involved in this circuit. If a fuse is blown, would the voltage be zero? Or does power come through a relay instead? Additionally, I'm unsure where the wires from pins 1 and 2 originate. Could the fuel pump relay be responsible for powering this heater circuit? Any insight into the correct testing procedure or wiring path would be greatly appreciated.

Related fault codes
P0036
Comments (4)
Anonymous 2015-05-21 08:51

A detailed wiring diagram would be very helpful — consider checking ALLDATA.COM for accurate schematics and component locations.

Anonymous 2015-05-21 11:18

Thanks for the suggestion. I found a diagram in my service manual, but it was not specific enough to assist with troubleshooting.

Anonymous 2015-05-21 13:06

THAT IS A PROFESSIONAL RESOURCE.... SHOULD HAVE WHAT YOU NEED

Anonymous 2015-05-31 11:13

The issue has been resolved. My manual specified testing voltage at the connector with the ignition on, but I initially tested it only when the engine was off — in that case, no 12V was present. The correct test condition is with the engine running. Once the engine was running, I measured 12 volts at the connector. Further testing revealed an open circuit in the heater wiring of the O2 sensor. It turned out to be a brand-new sensor that had a manufacturing defect — replaced and now the code has cleared.