At 09:58 PM 8/8/03 -0700, you wrote:
>I got a P0161 light. Passenger rear 02 sensor heating circuit.
>I figured since it's just the heater, and Southern California hasn't been
>extremely cold lately, I should be ok. Eventually the sensor will fail
>because it's not heated, and then I'll replace it.
The code is triggered when the pcm reads less than 30 millivolts for at
least 30-90 seconds from the rear O2 sensor. Generally, engine idle
after a cold startup and coolant temp is less than 150F is when this
dtc will happen.
Quite often a DTC is caused by open circuit used to power the component,
either a fuse is blown or has been erroneously removed. The rear O2 sensor
is protected by 2 fuses. Usually it's the lower amperage fuse that is either
missing or blown. The lower amperage fuse is positioned electrically in the
PDC or in the instrument panel Junction Block. See your FSM for location.
Check to see if fuse is there or blown. An O2 sensor heater, when damaged
or overheated, may short the circuit and cause the fuse to blow. The higher
amperage fuse is in the PDC but is not normally the cause of the DTC.
The following is a list of the components frequently replaced ERRONEOUSLY
due to an open fuse. Included are the possible DTC(S) which would be generated
as a result.
1. Oxygen Sensor (02)
* P0132 ($3E) = 1/1 02 Sensor Shorted to Voltage
* P0135 ($67) = 1/1 02 Sensor Heater Failure
* P0138 ($7E) = 1/2 02 Sensor Shorted to Voltage
* P0141 ($69) = 1/2 02 Sensor Heater Failure
* P0152 ($42) = 2/1 02 Sensor Shorted To Voltage
* PO155 ($7C) l= 2/1 02 Sensor Heater Failure
* P0158 ($7F) = 2/2 02 Sensor Shorted To Voltage
* P0161 ($7D) = 2/2 02 Sensor Heater Failure
2. Leak Detection Pump (LDP)
* P1495 ($B7) = Leak Detection Pump Solenoid Circuit
3. Evaporative Purge Solenoid (DCP)
* P0443 ($12) = Evaporative Purge Solenoid Circuit
4. Torque Converter Clutch -Solenoid (TCC)
* P0743 ($OC) = Torque Converter Clutch Solenoid / Trans Relay
Circuits
If the fuse is okay, most likely the sensor will need replacing.
If you've got a voltmeter or scanner, check for the proper supply voltage to
the heating element as well as that the circuit ground is good before
replacing.
The FSM should give the supply voltage (don't have mine FSM on hand). Verify
your diagnosis by unplugging the sensor harness and seeing that a read gives
a bias volt reading (whatever that might be?).
You didn't say if you tried to clear the code by disconnecting the battery
(it may have been a one time "fluke" situation). While the O2 sensor does
not affect performance or operability, the code will cause the pcm to stop
monitoring the EVAP and rear O2 sensor circuits so if other problems
in these areas crop up, you'll never know it. At least, that's my
understanding.
HTH.
Bob
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