05 Grand Caravan P0135

[rawdude]

Have about 55K on the van, started running a little bad sputtering and such, stalled a couple times. Check engine light came on and had a P0132 code; O2 sensor 1 in bank 1. Had the codes cleared was okay for a week or so then it casme back, same code. Bought a OEM Bosch sensor and the drivability problems went away, but the light came back on in a day or so. Drove the van from DE to GA, no issues, just the light was on. Checked the codes when I got back and had a P0135; O2 sensor heater circuit. Cleared the codes and came back the same day. Figured I got a bad sensor so I got another and just replaced it. On the way back on the test drive the light came on again; probably not a bad sensor. Any one have any ideas. The van runs fine, milage doesn't appear to have dropped greatly, if at all. Haven't had any rough idles or stalling since I replaced the first sensor.

I'm leaning toward a wiring problem, but I don't see anything obvious, looked while replacing the sensor the 2nd time. Didn't have the P0135 when the first sensor went bad. Ideas?????

[RIP]

No heat on an O2 sensor will only minimally effect mileage and driveability. The heater is there to quickly get the sensor up to temperature after a cold start so the engine will run more efficiently and cleaner. Once the engine gets hot, the heater is redundant.

No heat (P0135) on 3 sensors indicates something amiss in the wiring or the Powertrain Control Module (PCM). Take a second look at the wiring from the sensor connector to the PCM. The PCM powers the sensor heaters. On your van that means the brown/lt green wire from contact #2 on the upstream sensor connector to contact 18 on connector C3 on the PCM. Also check the black/lt green ground wire from contact #1 on the sensor connector. Look for pushed/bent connector contacts, melted/chaffed wire coating, etc. If you have and can use a multimeter test for continuity on those two wires.

[rawdude]

Thanks RIP, What did you mean by "No heat (P0135) on 3 sensors"? I understand the purpose of the O2 heater and realize this probably won't give me a drivability problem, but since my drivability problem went away after I replaced the O2 sensor I felt confident the origonal one was bad. I cleared the light a couple times now and the light comes back on after the 2nd start up. Meaning; I clear the light, take a short test drive, turn off the car, start it back up to take for another test drive and then the light comes on. Don't know if there is a built in logic of 2 consecutive failure or something like that to trigger the fault code.

I had read some other posts, in a different forum and someone mentioned to check the resistance of the O2 sensor. Made sense; measure the resistance of the heater element. They said check the resistance of the white wires going to the O2 sensor, but when I checked mine I didn't have 2 white wires at the sensor. I had 2 black, 1 blue, & 1 white. I don't have a wiring diagram and thought maybe the white and one of the black wires went to the heater. I checked the resistance and it was an open circuit, so I thought I might havew a bad sensor so I got another. Before installing the new sensor I took some measurements. The only wires I had continuity with were the 2 black wires ~2.8 Ohms. I checked this against the sensor in the car(the first one I installed) and the resistance was the same. The other forum mentioned the heater should have resistance of ~4.7 ohms; not sure if this is correct. I didn't have anything else to try and had the new sensor sitting in front of me so I stuck it in, but as I figured I had the same issue.

I didn't have the P0135 code with the origonal bad sensor which caused the drivability problems, only the P0132 code, so I'm not sure what has changed other then I installed the OEM bosch sensor. Wish I had the origonal sensor to check the resistance. I also went through tonight and checked all my fuses, because I saw that as a possible problem on another site. All the information on the other sites were for different year carvans, so I couldn't rely heavily on that information.

I looked over the connections at the connector and didn't see any problems. Do you know what the resistance of the O2 heater should be? I didn't run a continuity check of the wire from the sensor to the PCM though. Where is the PCM located? From your post I'm assuming I:
1. Check continuity between pin#2(brown/lt green) and pin#18(color??) at the PCM? Does the color stay the same? Which connector is C3 on the PCM? I'm assuming there will be more then one.
2. Check for continuity to ground of pin#1(black/lt green).

Have you seen problem areas where the harness gets chaffed or melted? Thanks again for all your help and let me know if you have any further suggestions. I'll look into the continuity measurements, but need to find the PCM first.

[jcardinal30]

yes i am also working a 05 and found that u must use oem sensors. the after market sensors havnt got the 2.5v bias voltage on the ground that they use right yet. in fact the oe sensors are cheaper than the aftermarket.