DTC P0138: HEATED OXYGEN SENSOR CIRCUIT HIGH VOLTAGE (SENSOR 2)

CIRCUIT OPERATION
• A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM (terminal No. 75) from the output terminal (terminal No. 1) of the heated oxygen sensor (rear).
• Terminal 2 of the heated oxygen sensor (rear) is grounded with ECM (terminal No. 92).
TECHNICAL DESCRIPTION
• The output signal of the heated oxygen sensor (front) is compensated by the output signal of the heated oxygen sensor (rear).
• The ECM checks for an open circuit in the heated oxygen sensor (rear) output line.
DTC SET CONDITIONS

Check Conditions
2 seconds or more have passed since the starting sequence was completed.

Judgement Criteria
• Heated oxygen sensor (rear) output voltage has continued to be 1.2 volts or higher for 2 seconds.
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are: )
• Heated oxygen sensor (rear) failed.
• Short circuit in heated oxygen sensor (rear) output line.
• Connector damage.
• ECM failed.