Two weeks ago the "Service Engine Soon" light came on on my 2000 Excursion V10 4x4. Today I pulled the codes and found P0135 and P0155, which are for O2 Sensor Heater Circuit Malfunction for banks 1 and 2. My truck only has the two O2 sensors pre-cat. I reset the codes, drove home from the parts store, and then started the truck up again a few hours later to go out and the light immediately came back on - presumably for the same codes. Normally if I received an O2 sensor error I would assume that it is just the sensors and change them, but if this is referring to the heater circuit for both sensors I wonder if that may have something else I should be looking for?
Truck will pass 101k miles tomorrow, and the O2 sensors looked pretty original to me last time I had the thing on the lift.
I would and try and check the connections to the 02 sensors and any connectors. Also the heaters in the 02 sensors themselves could just be bad. The fuse is number 19 for the sensors in the battery junction box like kieth w suggested I would check it also.
What does that mean?
This code refers to the front oxygen sensor on Bank 1. The heated circuit in the oxygen sensor decreases time needed to enter closed loop. As the O2 heater reaches operating temperature, the oxygen sensor responds by switching according to oxygen content of the exhaust surrounding it. The ECM tracks how long it takes for the oxygen sensor to begin switching. It the ECM determines (based on coolant temp) that too much time elapsed before the oxygen sensor began operating properly, it will set P0135.
Symptoms
You will likely notice poor fuel economy the illumination of the MIL.
Causes
A code P0135 may mean that one or more of the following has happened:
1. O2 Heater element resistance is high
2. Internal short or open in the heater element
3. O2 heater circuit wiring high resistance
4. open or short to ground in the wiring harness
Possible Solutions
1. Repair short or open or high resistance in wiring harness or harness connectors
2. Replace oxygen sensor (cannot repair open or short that occurs internally to sensor)
I would check connections as already suggested. But if that does not do it...then replace both O2 sensors.
Thanks for the suggestions! I'll start out by checking out the connectors and the fuse. If they seem fine, I'll just buy two new O2 sensors and change those out. At 8 years and 100,984 miles, it seems reasonable that they need to be replaced.
if you have a heater code after checking for voltage. in 99.9% of the cases the heater had burn't out.
code wise to set a fault the computer needes to go though 3 start drive tsets before it sets the fault.and from what you write .that is just what it did. if my truck i would get ready to change the sensers
Thanks for the suggestions! I'll start out by checking out the connectors and the fuse. If they seem fine, I'll just buy two new O2 sensors and change those out. At 8 years and 100,984 miles, it seems reasonable that they need to be replaced.
The nice thing if you have to replace the two O2 sensors is that it's really easy...and takes about 3-5 min per sensor. Lots of room...and with a O2 sensor socket...piece of cake.
Guess how I know? Yeah...back in November 2007...I had to replace my two "front" 02 sensors...at about 100k. I went with Motorcraft OEM...
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