Thread: p0138 help!
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Old 01-17-2013, 06:13 PM
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P0138 1/2 O2 Sensor Shorted To Voltage

answer on another website:

Inspect your wiring harness and sensor ground (Bk/Or).
With a DC voltmeter on the signal wire (Tn/Wt), see if the O2 volts does in fact stay above 1.2 volts. It should slowly walk up and down between ~0.2 - 0.8 volts.
The 'short to voltage' doesn't necessarily mean that you'll see battery voltage here. It simply means that the voltage is higher than allowed.

P0138-1/2 O2 SENSOR SHORTED TO VOLTAGE
When Monitored: With engine running for more than 2 minutes and coolant temperature
above 76C (170F).
Set Condition: The oxygen sensor voltage is above 1.2 volts.

POSSIBLE CAUSES:
O2S SENSOR GROUND CIRCUIT OPEN
O2S SIGNAL CIRCUIT OPEN
O2 SENSOR SIGNAL CIRCUIT SHORT TO VOLTAGE
WIRING HARNESS INTERMITTENT PROBLEM
O2 SENSOR
PCM
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