# '01 Altima ECM diagnostics/reset



## darkmaghir (Oct 14, 2005)

Can anyone help me reset my ECM or initiate the OBD2 diagnostics? 

My '01 Altima just failed Maryland emissions testing because of, (according to the DMV), an OBD2 Code P0110 "Intake Air Temp Circuit Malfunction." My Haynes manual told me to check the sensor supply volts (o.k. ~4.9vdc) and the sensor resistance hot and cold (o.k. hot:low & cold:hi). After all that, the "Service Engine Soon" was still illuminated.

Haynes also told me about the ECM OBD2 diagnostics/reset procedures, I went to try these, but my ECM doesn't have the LED's nor the mode selector screwdriver switch by which Haynes says you initiate diagnostics/reset, (just a piece of clear tape covering the holes in the box where they should be). 

I also tried disconnecting the negative battery terminal for a minute. After about 6-8 power-up/shut-down cycles, the "Service Engine Soon" light is still illuminated.

Does anyone have any advice for me; do I need an OBD2 scanner to do the reset?


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## darkmaghir (Oct 14, 2005)

Just a quick follow-up with some more info...

Apparantly some Nissan ECM's will reset or enter diagnostics self-test mode by following this procedure I found through another forum. I tried this today with no joy, I couldn't even get the dummy light to blink. So I am still looking for more ideas...

1. Key switch to "on," wait 3 sec.
2. Within 5 sec. repeat this five times: quickly depress accerator pedal fully, then release fully. Then wait exactly 7 sec.
3. Fully depress and hold accelerator pedal for 10 sec., the "Check Engine Light" should begin blinking OBD2 codes, count fast blinks for first (2) code digits, then slow blinks for second (2) code digits. Subsequent codes separated by a long pause, then all codes repeated continually.
4. Wait 10 sec. (min) then fully depress and hold accelerator pedal for 10 sec. to enter ECM self diagnostic mode. Result codes displayed as above.
5. Key switch to "off," to reset system to normal operation.

An independent shop mechanic who seemed familiar with this drill mentioned that even if I should extinguish the "Service Engine Soon" light by some means, the OBD2 failure codes may remain in the ECM until I have followed the 13-step "Readiness for Inspection/Maintenance (I/M) Test" procedure found in the owner's manual (p. 10-20). This involves highway driving @ 55mph then release accelerator pedal for 6 sec., quickly depress accelerator fully, then back to driving 53-60mph for 5 minutes minimum. Stop car, accelerate to 35 mph for 20 sec., stop, repeat accelerate to 35 mph for 20 sec. three times. (...blah, blah, blah...There's more to it, this is about half of it here, if you need the rest let me know. Maybe I'll try this tomorrow.) 

Thanks for any ideas you can offer.


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## flir67 (Oct 17, 2005)

*same problem*

I'm having the exact same problem on my 99 altima se. my light just came on a few weeks ago. I replace the air senor in intake tube before the air filter but still no go. 

I've read that it might be a short in the wires. how do you test to see if the air sensor is working hot and cold?


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## darkmaghir (Oct 14, 2005)

flir67 said:


> I'm having the exact same problem on my 99 altima se. my light just came on a few weeks ago. I replace the air senor in intake tube before the air filter but still no go.
> 
> I've read that it might be a short in the wires. how do you test to see if the air sensor is working hot and cold?



My Haynes manual covers this in slight detail as follows...
1. Disconnect the two-wire electrical harness connector from the Intake Air Temperature (IAT) Sensor (near and outboard of the battery, on top of the air intake duct, upwind of the air filter assembly).
2. Turn the ignition key switch to the "ON" position without starting engine.
3. With a volt meter, carefully probe/read the DC voltage across the two socket contacts in the female connector (wire harness connector). This is the reference voltage for the sensor supplied by the ECM, it should be approximately 5 vdc. The picture in the manual shows 4.88 vdc, my '01 Altima read at 4.89 vdc on my meter. If this reading is substanially lower but not zero, it may be a few things: ECM internal problem, short circuit between conductors or short to ground, or one or more poor connection(s) between ECM and IAT connector. Haynes sugguests it is usually wiring/connector-related, and it should be taken to a Nissan shop. If the voltage is dead zero, then the problem is likely to be an open circuit in the wiring between the ECM and the IAT connector, or a toasted ECM--check other ECM functions or ECM fuse to confirm this. 
4. Turn the key switch to "OFF." 
5. If the IAT reference volts are good , then check the IAT sensor as follows:
Probe the IAT sensor (male) connector pins carefully with an ohm meter, try not to bend the pin contacts. Read the resistance across the two pins on the sensor. It should be in the range of 1K-3K Ohms. If the car is cold, the reading should be close to or in the higher half of this range. It's hard to say exactly what it should be, because Haynes doesn't provide a table or chart for the exact resistance v. temperature relationship. After checking a cold car, then start the engine and let the car warm up to normal operating temperature. Repeat the resistance measurement on the IAT sensor as before. Now the resistance should be substantially lower. If the ohm meter indicates either an open circuit (or very high resistance: >.5M Ohms), or a short circuit (very low resistance: < 200 Ohms) across the IAT sensor, then the sensor itself is likely defunct.

(For this check I didn't bother following Mr. Haynes' method to run the engine to warm the car. I removed the IAT sensor from the intake duct and read its resistance while partially submerging it alternately in a cups of cool and warm water. Doing this yielded results quickly, and let me clean the sensor; mine read about 2.2K Ohms cool and about 1.5K Ohms warm. If I had to do it again, I would simply blow warm and cool air on it using a hair dryer.)

I hope this helps, good luck, and let me know if you have any success resetting your "Service Engine Soon" (MIL) light.


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## flir67 (Oct 17, 2005)

*unit will reset automatically*

I installed the new part the p0110 air sensor and after the install the light was still on. I drove for a few days and about 200 miles later the light automatically will reset. its just takes time but make sure u replace the right part.

good luck to all.


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## stanen8871 (Apr 15, 2003)

You could go to Autozone, they will check your OBD codes and reset your light for free.


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## darkmaghir (Oct 14, 2005)

flir67 said:


> I installed the new part the p0110 air sensor and after the install the light was still on. I drove for a few days and about 200 miles later the light automatically will reset. its just takes time but make sure u replace the right part.
> 
> good luck to all.



Thanks flir67, I'll take another look at the codes to see if they're still set and then try a new sensor next.


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## darkmaghir (Oct 14, 2005)

stanen8871 said:


> You could go to Autozone, they will check your OBD codes and reset your light for free.


I plan on getting a code scanner, I imagine as the years go by my friends and I will have other codes to scan for. 

But are you saying that reading the codes on this type of ECM also causes them to clear if the fault has been corrected?
Thanks


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## flir67 (Oct 17, 2005)

*could not reset at autozon*

I've been to 4 autozones, and none of them could clear the error messages. the scanner said link failure after it found the problem. so I'm gladed mine cleared itself like it did.

getting a scanner is nice, I might get one in the future as everythign is computerized these days but I have a hard time justifing 200.00 for the good model for use maybe once in year or years.



good luck.


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## darkmaghir (Oct 14, 2005)

flir67 said:


> I've been to 4 autozones, and none of them could clear the error messages. the scanner said link failure after it found the problem. so I'm gladed mine cleared itself like it did...
> 
> 
> For reasons beyond my comprehension, my Altima's SES light decided to turn itself off this morning. Maybe the evil spirit residing in my ECM had better places to haunt today, or maybe some children to torment.
> ...


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## nigeleccleston (Nov 27, 2006)

*Use smaller screwdriver*

I found your post useful. I notice you thought you did not have a screw to turn in your ECM. I thought that too, but finally discovered I needed to use a very small screwdriver to engage it - 2.0 mm. Also it was behind a plastic label I had to peel off.
I also tried the accelerator pedal method to no avail - I think this is for 2002 and newer.
The ECM on a 2000 Altima GXE is behind a plastic kick panel to the right of the accelerator. You can get the screwdriver in without removing or loosening the ECM.


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## Dgarcia081 (Mar 7, 2008)

hey i need help i need to find where my intake air temperature sensor is if anyone can help out hit me up at [email protected] asap thanks


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