Codes P1135 and P0139?

Tiny
ALEXIS NICOLE TAYLOR
  • MEMBER
  • 2001 FIAT PUNTO
  • 1.2L
  • 5 CYL
  • 2WD
  • MANUAL
  • 80,000 MILES
Hi, the car is acting a little strange. The first thing I noticed was the central locking system stopped working I know this is not a fuse as I checked the fuse box, and I can hear it click with I attempt to lock but none of the locks try to engage. I didn't think anything of it until this morning when I tried to start the car and nothing happened no dash lights or anything, this made me think it was the battery but when I flicked the overhead light on it came on and suddenly the car was fine. I started driving and got an engine light, so I took the car to have the code read and it came back with p1135 and p0139, manufacturer control and o2 sensor bank 1 number 2. I'm not sure what to do at this point and if I can keep driving it without damage or if these problems are something I can fix myself. Also, I know this is likely related to the o2 sensor but the car stutters in 1st gear.
Thursday, October 19th, 2023 AT 5:53 AM

3 Replies

Tiny
BORIS K
  • MECHANIC
  • 836 POSTS
Hello,

P0139 - oxygen sensor downstream from catalytic converter slow response
P1135 - oxygen sensor heater circuit upstream from catalytic converter

So, both oxygen sensors are affected.
Regarding the slow responding oxygen sensor 2, is there perhaps an exhaust leak on the front exhaust pipe/exhaust manifold?
If so, have this seen to first.

P1135, heater circuit can be caused by a bad connection at the O2 sensor, no 12V supply to heater circuit, faulty heater or faulty heater control/ground from the ECM.

Pin out at upstream O2 sensor
Pin 1, yellow/white wire signal to ECM
Pin 2, green/yellow wire signal to ECM
Pin 3, pink/white wire heater circuit control to ECM
Pin 4, brown/white wire 12V supply from fuse F11 in engine fuse block

Oxygen sensor test
https://www.2carpros.com/articles/how-to-test-an-oxygen-sensor-02-sensor
and
https://www.2carpros.com/articles/how-an-oxygen-sensor-works
and
https://www.2carpros.com/articles/how-to-replace-an-oxygen-sensor

I do not think that these O2 sensor issues will cause the non-start problem. They might cause the hesitation/stuttering issue.

Suggest to check and clean the main ground points in and around the engine compartment, battery terminals and connections at the engine fuse block

Hope this helps.

Cheers, Boris
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Thursday, October 19th, 2023 AT 9:21 AM
Tiny
ALEXIS NICOLE TAYLOR
  • MEMBER
  • 5 POSTS
Thank you so much, this is really helpful. Do you think it's okay to drive the car with the o2 sensor not working correctly? I don't have a lot to try and fix it right now but also don't want to damage the car.
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Thursday, October 19th, 2023 AT 9:27 AM
Tiny
BORIS K
  • MECHANIC
  • 836 POSTS
Hello,

It will be ok to drive with these oxygen sensor faults; the ECM will use replacement values to compensate for the absence of the O2 sensor signals. The fuel economy will suffer though.
Keep in mind that the vehicle will not pass a MOT or roadworthy check, depending on which country you live in.

Cheers, Boris
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Friday, October 20th, 2023 AT 2:31 AM

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