DTC P0136: 1/2 O2 Sensor Heater Circuit Malfunction: Description

The 1/2 Heated Oxygen Sensor (HO2S) may be referred to as a downstream oxygen sensor. The 1/2 HO2S is located in exhaust pipe behind left catalytic converter. The 1/2 HO2S heater circuit is monitored when ignition is on and battery voltage is more than 10.4 volts. DTC may be stored in Powertrain Control Module (PCM) if PCM relay control circuit between PCM and oxygen sensor relay does not match desired stated. Possible causes are:

Open Circuit Between Oxygen Sensor Relay & Fuse "U" (20-Amp)
Open Circuit Between Oxygen Sensor Relay & PCM
Open Coil In Oxygen Sensor Relay
Blown Fuse "U"
Faulty PCM
Short To Ground Between Oxygen Sensor Relay & Fuse "U"
Short To Ground Between Oxygen Sensor Relay & PCM
Intermittent Condition In Wiring Harness