Good evening everyone, having a very frustrating issue here that is preventing me in getting a state inspection because of the Service Soon Light. The 2 codes noted above continue to come on even though I've replaced the crankshaft position sensor and O2 sensor(bank 1 sensor 2), both with geniune Nissan parts. Symptoms include: hard to start, rough idle and acceleration and rpms limited to 3000 no matter what gear it's in. Is this the ECU that has failed? If so, wouldn't I get a code for the ECU failing? I tested the voltage, both sensors are getting 12V. Is it something at the front like intake of air or mixture of air and gas? Wouldn't I get a code for that, like a mass air flow sensor? Please help, I love my 2004 M45 ❤

The CKP connector E317and Bank1 rear O2 sensor E319 are on the same leg of the E Harness on the righthand side of the tranny. I'd say there's a very good chance the harness has been damaged by chafing or road debris. See PG-35 here:
https://www.nicoclub.com/service-manual ... 5%2Fpg.pdf

Thank you VStar, I was hoping that's not the case since the wiring harness in that particular is in a cramped area. Looking at the diagram, you sent me, I had a mechanic replace my starter right before I started having these issues. Is it possible he did something with the wiring leading to the crankshaft sensor and O2 sensor?

mrkoffee77 wrote: ↑

Sun Oct 09, 2022 10:40 pm

I had a mechanic replace my starter right before I started having these issues. Is it possible he did something with the wiring leading to the crankshaft sensor and O2 sensor?

Yep. Not necessarily anyone's fault, though. With a harness that old, sometimes just needing to move it around can cause issues.

VStar, sorry to bug you. Is it fair to say that if both sensors are getting voltage, then the issue is the incoming signal wire of either sensors? A pinch or cut somewhere? I'm trying to narrow down the search as much as possible.

No, you need to make sure they have both power and ground, and in the case of the heater there can't be a lot of resistance in the wires to and from the ECM. Use a test lamp with a regular bulb to check power and ground, test from the power pin to the ground pin and you should get bright light. If you get a dimbulb or no bulb then there's resistance or a break in the circuit (the latter will be on the ground side, since you tested power). The reason you use an incandescent bulb for checking power circuits is that the bulb itself needs power. That tells you the circuit is healthy under load, something a VOM will only tell you if you test dynamically with voltage drop.

Hello all, just an update. I found that wire hireness had a short. Once replaced, my car was back to running super smooth and quiet....with 1 problem. The P0037 code popped up which is bank 1 sensor 2 low circuit. I checked to see if the sensor was getting voltage. It was good. I checked for continuity for the heating element, that was good. While disconnected and car was hot, I checked the voltage readings and it was showing between .8 and .9 volts, lean but within range. I checked the harness, I was getting 12 volts while the car was off. Checked for continuity between the harness and the ECU, good to go. Checked the 2 o2 fuses in my fuse box, both good. With all this I replaced my OEM Nissan o2 sensor, which I put on before I knew the harness was shorted, with an NTK sensor which is direct fit not Universal. Reset the light and drove 50 miles. I had my FixD code reader on and see that while I'm driving the short and long term fuel trims are near 0% which is great but when I let go of the gas pedal or I'm at idle, the long term trims are down to -10.16%. Short trim still good, hovering at 0% with slight +/- 4 point fluctuations but well within range. Engine light still comes on. What am I doing wrong. Oh by the way, the MAF sensor is new as well showing 6.5 grams which I hear is normal for an 8 cylinder. Please help, this is now with expired state inspection and expired registration. Just trying to get it street legal.

The -10% LTFT is weird. It means the ECM is having to lean the mixture from normal, opposite from a vacuum leak. It could be a leftover, but if it's real, the only thing which can really cause that on both banks is a MAF which is under-indicating. Have you tried clearing out the long term trims and running an IAVL on it?

How do you clear out the long term trims? I saw a video on YouTube stating to unplug the MAF, turn on the car for at least 10 seconds and then shut it off. Is that how you do it?

That works on most of the older stuff, inducing a P0102 for a flatlined MAF causes the ECM to clear its memory. IIRC it should work on just about anything prior to '12. Try it, your scanner will read 0% LTFT if it works.

My scanner is a $20 FixD code reader lol I'm not a mechanic, well I'm a mechanic via everything I've learned so far online. Could you walk me how to do this reset without a scanner?

You said your LTFT was at -10.16%, so your FIxD must be able to read it? To clear the LTFT (self learning), try this:
1 Start engine and warm it up to normal operating temperature.
2 Turn ignition switch OFF.
3 Disconnect MAF harness connector, restart and run engine for several seconds at idle.
4 Stop engine and reconnect MAF.
5 Make sure DTC P0102 is displayed.
6 Without restarting, erase the DTC.
7 Run the engine for 10 minutes at idle speed and check that LTFT is cleared.

Thank you so much, going to try it out!

So it looks like the reset worked. When I started the car after the reset, the short terms were both around +20% and long terms at -10%, after a few minutes you could tell the computer was beginning to correct itself. But bank 2 looks like it corrected after 10 minutes. Bank 1 still trying to correct. Long term on bank 1 is stuck on -8.59%, short term goes up to 23% then drops to 0% then climbs up to 23% again before it drops back down to zero. Going to drive it to see if it can correct.

Ok back home now. Driving on the hwy, numbers looked great. Got off the hwy to head home. Pulled over, shut the car off a few blocks away from home. Waited a full minute. Turned the car back on, started driving home and the service engine light came back on, P0037. Frustrating. I might have messed up the order of these pics i uploaded. Yup start from bottom up.

I saw a few videos on YouTube suggesting that perhaps there's too much fuel pressure but wouldn't that be caught by sensor #1 as well? Also an exhaust leak after sensor 1 but before sensor 2 may be giving me inaccurate readings? Lastly, during the time my harness was shorted, it was dumping fuel into the motor like crazy. Could it have ruined my catalytic converter? If so, wouldn't i get the code for the catalytic converter? Also, the dumping of fuel in the motor could have tainted my engine oil?