P0155 code - tearing my hair out.
05-05-2016, 10:30 AM
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P0155 code - tearing my hair out. Hey guys,
Finally at wits end with this one, so thought I'd drop in and see if the pros can help me out here. Just finished up my 2005 LQ9/4L80E swap into my 88' squarebody crew, and everything seems to be working great, except for this O2 heater code! It's driving me up a wall. The O2s are setup as case ground, so the heaters are not PCM controlled. I am ONLY getting the code on B2S1. This O2 is actually the closer to the exhaust manifold outlet than B1S1, so it shouldn't be related to placement. Blue/Green PCM and DBW.
So far I have:
1) Swapped sensors side to side (ACDelco AFS75). Code stayed on B2S1.
2) Replaced the sensor with a Denso. Code stayed on B2S1.
3) Verified 12V on the ignition+ to the heater.
4) Verified resistance on 12v+ to heater is OK (0.5 ohms).
5) Verified resistance on ground to heater is OK (0.3 ohms).
6) Checked resistance on the O2 heater itself (ACDelco was 20 ohm, Denso 7 ohm).
6) Verified continuity between various grounds to the heater ground)
7) Test light from heater 12v+ to frame ground (it lights brightly)
8) Test light from heater 12v+ to heater ground (also lights brightly)
9) For kicks, test light from heater 12v+ to B1S1 heater ground (lights brightly).
10) Used HPTuners to verify PCM is receiving a signal from the O2. It is sluggish compared to B1S1 until driven around and hot, but is receiving a signal.
11) Torn hair out.
12) Thrown things.
13) Pondering setting truck on fire.
The only thing I have not yet done, is verify the resistance on the PCM signal wires, but it seems...unlikely, to my untrained self. I plan to do that today, but wanted to get this out there and see if anyone had any other suggestions before I burn the thing to the ground?
Finally at wits end with this one, so thought I'd drop in and see if the pros can help me out here. Just finished up my 2005 LQ9/4L80E swap into my 88' squarebody crew, and everything seems to be working great, except for this O2 heater code! It's driving me up a wall. The O2s are setup as case ground, so the heaters are not PCM controlled. I am ONLY getting the code on B2S1. This O2 is actually the closer to the exhaust manifold outlet than B1S1, so it shouldn't be related to placement. Blue/Green PCM and DBW.
So far I have:
1) Swapped sensors side to side (ACDelco AFS75). Code stayed on B2S1.
2) Replaced the sensor with a Denso. Code stayed on B2S1.
3) Verified 12V on the ignition+ to the heater.
4) Verified resistance on 12v+ to heater is OK (0.5 ohms).
5) Verified resistance on ground to heater is OK (0.3 ohms).
6) Checked resistance on the O2 heater itself (ACDelco was 20 ohm, Denso 7 ohm).
6) Verified continuity between various grounds to the heater ground)
7) Test light from heater 12v+ to frame ground (it lights brightly)
8) Test light from heater 12v+ to heater ground (also lights brightly)
9) For kicks, test light from heater 12v+ to B1S1 heater ground (lights brightly).
10) Used HPTuners to verify PCM is receiving a signal from the O2. It is sluggish compared to B1S1 until driven around and hot, but is receiving a signal.
11) Torn hair out.
12) Thrown things.
13) Pondering setting truck on fire.
The only thing I have not yet done, is verify the resistance on the PCM signal wires, but it seems...unlikely, to my untrained self. I plan to do that today, but wanted to get this out there and see if anyone had any other suggestions before I burn the thing to the ground?
05-05-2016, 10:42 AM
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If i had to guess you have a wiring issue between the PCM and the o2. I would check the wiring starting at the o2 and work your way back, If there is a break in the wire.or splice it would allow voltage but not current. Had a issue like this before on a powerstroke, The wire has gotten pinched and broke come of the conductors. Could see voltage, and omed great, but when there was a high current load the wire would not pass it. Replaced the wire from the PCM to the VGT and all was happy.
BTW setting the truck on fire is not a good way to heat a O2 sensor
BTW setting the truck on fire is not a good way to heat a O2 sensor
05-05-2016, 06:47 PM
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If i had to guess you have a wiring issue between the PCM and the o2. I would check the wiring starting at the o2 and work your way back, If there is a break in the wire.or splice it would allow voltage but not current. Had a issue like this before on a powerstroke, The wire has gotten pinched and broke come of the conductors. Could see voltage, and omed great, but when there was a high current load the wire would not pass it. Replaced the wire from the PCM to the VGT and all was happy.
BTW setting the truck on fire is not a good way to heat a O2 sensor
BTW setting the truck on fire is not a good way to heat a O2 sensor
In the meantime, I ran a new log today where I let the O2s heat up before firing the engine. It (B2S1) didn't seem as sluggish (in fact, it seemed to heat up faster, possibly due to the Denso sensor having a lower resistance and allowing more current flow).
Here is the HPTuner log, if anyone is interested (right click, save-as). It honestly looks fairly normal to me in most instances, but it is slightly different than B1S1's pattern.
https://foamypirate.com/img/88chevy/...0155_50516.hpl