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Discussion Starter · #1 ·
So the my 1998 S79 GLT keeps throwing the 2 O2 sensor codes

P0132
O2 Oxygen Sensor Circuit High Voltage (Bank1, Sensor1)

and

P0138
O2 Oxygen Sensor Circuit High Voltage (Bank1, Sensor2)

I have replaced both o2 sensors with factory replacements.

When I check the voltage of the sensors the front sensor varies from 0.1-0.9V but the rear sensor is stuck at 1V.

I have already checked for shorts and non of the wires are shorted together.

I have read that it may be the o2 sensor heater circuit.

Does anyone know how to check the o2 sensor heater?

If I'm off course does anyone have some advice?
 

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If you are testing at the end of the terminal, you may have a bad wire or ground. Test the same wire at the ECU and look for the following values:
Front sensor
A32 should be key on engine off: 1.1-1.2V and key on engine on 0.0-0.9V
A33 should be key on engine off only at roughly .7V
Rear sensor
A34 should be key on engine off ground 0V or key on engine on idle 0.6V and .0 -.9V depending on load.
 

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Discussion Starter · #3 ·
I finally got around to testing the circuit.

A32 = 1.21 V
A33 = 0.75V
A34 = 10.5V

All of these measurements were taken with the key in the on position and the engine off.

A34 seems very high. Any one have any advice on this?
 
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