Code P0056 - '01 LW300

SES light came on the other day and I did the usual first try of pulling the
fuse to reset the controller. I had gotten gas the night before and it was
plausible that this was a problem. No good, Engine started and light stayed
off but came on again at next engine start.

Borrowed a Snap-On scanner from a friendly garage and found the following
codes set:
P0056 HO2 heater circuit bank2 sensor2
P0161 O2 heater circuit bank2 sensor2
P0160 low O2 activity bank2 sensor2
P0159 O2 sensor slow bank2 sensor2

Following resetting the codes, the P0056 came up again immediately so, guess
that is the primary problem. Will pick up a new sensor tomorrow. Engine has
98K on it so can't complain that it needs a new sensor.

Scanner shows that both upstream O2 sensors (sensor1) are running in closed
loop and are normal. Both downstream sensors show open loop but that is
normal as I understand it.

The problem sensor is the bank2 (against firewall) downstream. If there is
no compelling reason to replace both sensors, just going to replace the one
(but with a Bosch sensor).

 

My buddy at the garage identified bank 2 improperly as being against the
firewall. Bank 2 is front (against radiator). Checked this from the service
manual.
Pulled the connector and tested heater circuit with ohm meter and it was
indeed open. Getting the connector apart was the hardest part. First the
latch holding the connectors to the bracket is gently squeezed with a pliers
to release it. The red latch mechanism was pretty stuck and I had to beak
off a few black tabs in order to get it to move. The red latch gets pried
out to the side to release the O2 sensor connector. To re-attach it, gently
mate the connectors and push in the red latch slide to lock in place.

Bosch universal sensor cost about $100 and came with the necessary splices
to use the original connector. Codes reset and all good now.

Since the harness was run in such tight quarters, before pulling out the
original sensor harness, Tie a string to the connector and as the harness is
pulled out, it pulls the string through and makes it easy to pull the new
harness into position.

Oppie