I have code p0155 bank 2 sensor 1 .But I tested with two scanners they show both pre cat sensors are working, voltage .120 -.870 and .095 =.830. both the long and short ft are within proper range. Post cat sensor seem to bounce around, the other day it flat at .130 , then yesterday it was flat at .759, today it was between .350 =.550 averaging .460 which I believe is ok. I cleared the codes to get the freeze frame info. First Freeze Frame as follows,fuel sys.1 ol,fuel sys.2 ol,load %4.3, Ect 125, shrtft 1 -6.3 , shrtft 3 -99.2 ,longft 1 7.0 , longft 3 -99.2 ,shrtft 2 -5.5 ,shrtft 4 -99.2 , longft 2 3.9 ,longft 4 -99.2 . Map 6.1 ,Rpm 644 ,Vss 0 , Maf 0.02 ,Tp 0.0 .The second Freeze Frame as follows Fuel sys 1 cl, Fuel sys 2 cl ,load %2.7 ,ect 195 ,shrtft 1 =12.5 ,shrtft 3 -98.4 ,longft 1 -6.3 ,longft 3 -98.4 , shrtft 2 -10.9 ,shrtft 4 -98.4 ,longft 2-7.0 ,longft 4 -98.4 ,Map 4.5 ,Rpm 634 ,Vss 0 ,Maf 0.01 ,Tp 0.0 .I also replaced spark plugs,complete distributor with cap and rotor. I don't know what the different long and short fuel trim # ie: 2,3,4 ect. mean ,Any help is appreciated,Thanks
o2 sensor problems p0155
- Thread starter talgoo
- Start date
Molson02536
New member
Code P0155 is set when the O2 sensor is starting to get lazy. Start with the simple, check check your fuses (02 15A fuse - under-hood box) and grounds to the O2 sensor first because there is always that remote chance that the only issue is a blown fuse or a bad ground. Verify that there are 12-volt heater signal(s) and good ground(s) to the sensor and that the Engine Coolant Temperature Sensor is reading well within the closed loop envelope and that its readings don't go below 160º F when the vehicle is driven, especially above 60 KM/H = 45 MPH.
If there good then switch the O2 sensor from left to right sensor and see if the codes change to P0135 which is a Bank 1 sensor 2 heater malfunction. If the codes change, then replace the O2 sensor
Hope this helps
Molson02536
Molson02536
New member
Yes i have, thats why i am thinking its getting lazy and replacing it would address the issue. But to be sure and save time and money, switch the O2 sensors and see if there is a difference.
If there is no difference, than its going to be checking the wire harness to make sure there good and that ground is good.
Keep us posted and be safe
Molson02536
I just checked wiring it looks ok .No indication of water or heat damage.tested wire have ground and 12.83v Fuse is ok.Is bank 1 sensor 2 behind the cat. can they be switched with bank 2 sensor 1 that is before the cat or am I back asswords,Thanks again for your time.
Molson02536
New member
"P0155 02 Sensor Heater Circuit (Bank 2 Sensor 1)" it's "the passenger side front sensor" Just swap it out with the one from the drivers side down pipe and see if the codes switch to P0135 which is (Bank 1 Sensor 1)
Spray it down with penetrating oil and use a O2 socket to remove and re-install the new O2 sensor.
Keep us posted
Molson02536
Thanks for the info ,for some reason I thought the exhaust ran down drivers side, so I would have Bank 1 sensor 2. But I was wrong, so would that make down stream sensor Bank 2 sensor 2.Anyways I used wd ended up wrecking sensor.I'ii pick up new one AM.I"ll let you know how I made out,Thanks again I really appreciate your help.
Well finally managed to install new sensor,seems to run little better,I will drive it a day or two, Both pre cat sensors are working with in parameters,the back sensor moves slowly and moves between 650-750.It still is a little hard to start.I will keep you updated,thanks
Molson02536
New member
No worries about the post cat O2 sensor, its readings has no influence on how your engine will perform. The post O2 sensor is there to monitor the catalytic converter as to its condition, in short. Is the catalytic converter still working within its parameters.
Try this if your still having hard starts, cycle your ignition 3 times before you try to start the Jimmy. If it does, then there is a good chance that your return fuel pressure check valve has gone bad. The bad news is that, its a part of the fuel sending unit.
After you cycle the ignition and still having hard starts. Check your fuel pressure at the shreddar valve. You should get a reading of 62-65 psi ignition on and engine not running. Once the engine has started, the pressure should drop around 5 psi.
Keep us posted and we can go from here
Molson02536
Molson02536
New member
Turn your ignition on and off 3 times waiting for your check engine lights to go off on your dash before you turn the ignition switch off and then on again. The 3rd time, try to start the engine and see if it starts easier then it has been.
Post back and be safe
Molson02536
Hi again,Thanks again for all your help ,I have no idea what and where a shredder valve is,I hope it is not in gas tank ,that would suck.Will any pressure gage be ok to check the psi.Is it normal for evap monitor to take this long to cycle through,There still is no check engine light on,The replacement of o2 sensor fixed the other problem I had all sensors are working, Thank you ,you saved me lots of money and a trip to the nut house.
Molson02536
New member
Low fuel pressure from a weak fuel pump or a bad check valve for the return fuel line will not set a check engine light.
You do have good fuel pressure when starting up the Jimmy, cause if you don't have at least 62 PSI of pressure. The engine will not start, if the fuel pressure is slightly under 62 PSI will give you hard starts.
Loosing the fuel pressure prim will also cause hard starts cause it takes a few seconds longer to build up to the 62 PSI of pressure to get the engine started. The fuel pressure prim is lost when the return check valve has gone bad, but that valve is apart of the fuel sending unit in the gas tank.
The fuel Schrader Valve is located on the fuel line on the divers side by the distributor, it looks like a tire stem valve with a cap on it. Your going to have to use a Fuel pressure gauge. Get a reading with the ignition turned on engine not running and you should get 62-65 PSI then turn the keys off and see how fast you loose your pressure, it should hold steady for 5 min then slowly go down. The pressure should only drop about 5 PSI when the engine is started.
Start with the simple and replace your fuel filter first, its the easy to replace and in expensive. The fuel filter is located on the inside frame rail under the drivers door.
Keep us posted and be safe.
Molson02536
Hi again ,just tested fuel pressure ,it reads 52. psi when I turn key on after a couple of seconds it drops to o psi without touching the key. If I start it up it reads 52 psi. but returns to 0 psi. as soon as I shut it off , The service manual indicates pressure of 55-60 psi.Any idea what this means.does this indicate a faulty fuel pump (it is only 3 psi. off normal operating) or is the pressure check valve or something else.Thanks again for your help.
Molson02536
New member
Could be a bad ground to your fuel sending unit which can give you low psi, a rapid falling of fuel pressure could be one of two things. 1, a bad return fuel pressure check valve which is apart of the fuel sending unit. 2, a bad fuel pressure regulator which is leaking, hut in most case the engine would throw a running rich dtc code.
Start with the simple and check the ground wire to your sending unit, the harness runs to the cross frame rails where the ground wire is mounted to. Also replace the fuel filter when you can to buy you more time for your them sending unit.
The sending units have a life expectancy of about 150,000 miles and anything after that is borrowed time. With the dropping of the fuel pressure rapidly when the switch is turned of is the cause of the hard starts from low fuel pressure rising to 62 psi, so cycle the ignition till you can address the issue. Or its from a leaking fuel pressure regulator, and that's located in your upper intake manifold with your fuel injectors.
Keep us posted and start with the inspection of the ground wire and replacing the fuel filter.
Molson02536
Hi ,thanks so much for the info.I checked the fuel pressure again the pressure was 60 psi not 50 psi?. so I removed spider injector, The area on the bottom seemed really clean ,The spider assembly seemed to have oil residue all over it ,but not excessive for 220,000 km.To me it seems that fuel must be leaking in there some where as the area was too clean.Do you have any idea's on how to check the pressure valve, the spider assembly and the fuel injectors for leaks.Keep in mind the unit is disassembled,Thanks again for you help.
Molson02536
New member
Inspect the fuel pressure regulator, you should be able to see if its been leaking from how clean it is from the rest of the area.
Replace it if it had gone bad or if its questionable, there not that expensive, and if you have some extra cash around. This would be a great time to upgrade your spyder fuel system and replace it with the multiport injection system which is much better and more durable.
Its a plug and play upgrade so the existing wiring system will hook right up.
Keep us posted and keep up the great job
Molson02536
The pressure sensor and spider assembly was fairly clean, except for a thin oil residue covering it, but I have no way of knowing if it looks the way it should. I've never taken one apart before! But the bottom of the plenum seems to be really clean. I have attached a couple of photos of what it looked like when I took it apart. To me it seems to be way too clean. What is your opinion?
Is there any way that I can check the pressure valve and the spider assembly with the units out of the vehicle? Sorry to be a pest but does anyone out there know a supplier that is reasonable in their pricing and not charge a fortune for the spider assembly,2003 gmc jimmy 4.3 .I live in canada so some of the companies will not ship here.
Thanks again for all your help!
Is there any way that I can check the pressure valve and the spider assembly with the units out of the vehicle? Sorry to be a pest but does anyone out there know a supplier that is reasonable in their pricing and not charge a fortune for the spider assembly,2003 gmc jimmy 4.3 .I live in canada so some of the companies will not ship here.
Thanks again for all your help!
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