Looking for input

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Lwduppong
Posts: 1
Joined: Fri Oct 06, 2017 7:31 pm
Car: 2002 Sentra Spec V

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Looking for any input on an issue i have with my 2002 SpecV. I've worked on cars my entire life and worked in shops for years so I I know my way around a vehicle, But this is my first venture into the Nissan world.

The problems i am having are
1. setting code p0031, O2 sensor heater control circuit low. Code would set immediately after clearing the code initially. Now it sets the code but it takes longer to turn on the light on.
I speced the o2 heater and it showed 9.8 ohms. I Had another used sensor which speced identical. Nissan specs say 3.7. I had a new sensor on the shelf which spaced 3.6. I have full 12 volts at the plug in and no resistance on the ground side. I installed the n ew sensor and that is when it started to take longer to turn on the check engine light. I pulled the ECM and checked the wiring between the 2. No resistance, short to power or ground.

2. The temp gauge goes full scale shortly after the engine starts warming up...i.e the car may run for 2-3 minutes and the gauge starts climbing steadily until it goes full scale. Car is not overheating, not pressurizing the system the fans cycle normally. I checked the temp sensor, 2 wire, specs and it was within the manual specs. I had another used sensor that speced out normal and had the identical problem. Voltage, ground and the wiring check out fine.

One other thing i noticed while using my scan tool is the CTS was showing -40 deg when the car was sitting in a 70 degree garage not running. After the vehicle warms up it shows 185 deg and doesn't fluctuate. I can rev the engine until the fans kick in and it won't read any higher than 185.

I'm afraid it's an ECM issue.

Has anyone run into this issue?
Any input is appreciated.


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centralcoaster33
Posts: 2769
Joined: Tue Apr 05, 2005 10:41 am
Car: 240SX #5-1997
Location: Central Coast, CA

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Welcome to NICO Club!

Does your coolant circulate once at operating temp? Have you considered replacing the coolant temp sensor that goes to the gauge cluster? I'm not one to throw parts at an issue typically, but when I have to boil water and use a thermometer and then measure resistance and the part is only 15 bucks, I just buy the part. Actually I look around my garage for a spare first. :)

I'd put in the new O2 sensor and monitor results as you have. I'd use the FSM for details on the procedures. Here's a link to the chapters (you can dowload it all as PDF documents using the download arrow in the upper right corner of the document viewer.
http://www.nicoclub.com/FSM/Sentra/2002/


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