Nissan/SR20 gurus......please help.
10-14-2008, 02:01 PM
#11
Administrator
Join Date: Nov 2002
Location: أنا لست إرهابيا
Posts: 10,636
Likes: 0
Received 0 Likes
on
0 Posts
Re: Nissan/SR20 gurus......please help.
MASS AIR FLOW SENSOR MALFUNCTION
If the mass air flow sensor output voltage is below the specified value, the ECM senses an mass air flow sensor malfunction. In the case of a malfunction, the throttle position sensor substitutes for the mass air flow sensor.
Although the mass air flow sensor is malfunctioning, it is possible to start the engine and drive the vehicle. But engine speed will not rise more than 2,400 rpm in order to inform the driver of fail-safe system operation while driving.
If the mass air flow sensor output voltage is below the specified value, the ECM senses an mass air flow sensor malfunction. In the case of a malfunction, the throttle position sensor substitutes for the mass air flow sensor.
Although the mass air flow sensor is malfunctioning, it is possible to start the engine and drive the vehicle. But engine speed will not rise more than 2,400 rpm in order to inform the driver of fail-safe system operation while driving.
__________________
Got a 1995-1996 240SX? Want a new front bumper?
Check this out. Posting on drag first to try and avoid shipping it.
Got a 1995-1996 240SX? Want a new front bumper?
Check this out. Posting on drag first to try and avoid shipping it.
10-14-2008, 03:52 PM
#12
Racetracks
Join Date: Nov 2002
Location: How long is a piece of string?
Posts: 15,668
Likes: 0
Received 0 Likes
on
0 Posts
Re: Nissan/SR20 gurus......please help.
Yeah, the resistance checked within the specified range the way it was adjusted. At WOT though, it went up twice as high as it should have (10k ohms rather than 5k). I swapped it with a TPS from a known running car, and that sensor did the same thing.
It completely confused me, until I realized that the TPS probably reads a max of 5k ohms with the pedal to the floor, rather than with the throttle body opened all the way by hand; I probably rotated it too far. I felt dumb after that.
It completely confused me, until I realized that the TPS probably reads a max of 5k ohms with the pedal to the floor, rather than with the throttle body opened all the way by hand; I probably rotated it too far. I felt dumb after that.
Really though, the resistance of the TPS doesn't matter, only that it is functioning properly (meaning it is changing resistance with angular position). The output voltage is what needs to be checked and calibrated if the sensor is capable of being moved.
So here is how this works. The TPS is a variable resistor (potentiometer), so it will put out a resistance somewhere between the lowest and highest value (depending on position obviously). The way TPS sensors are wired, the TPS presents a fixed resistance to the ECU from end to end, which are the 5VDC and GND terminals. This resistance doesn't matter, it can be 2k, 5k, 20k, whatever.
The signal output is just the proportion of where the wiper (the moving part) is in relation to the ends. So if the wiper is a 5th of the way toward the 5VDC end of the potentiometer, it will put out 1VDC, regardless of the total resistance of the TPS. This all assumes though that you have 5VDC at the sensor, and not less or more than that. That is why it is often more helpful to check the voltage instead of the resistance. if you know what the voltage should be at idle, and at WOT, for example, and you're out of that range, you know that you may need to rotate the TPS or track down a problem with terminal corrosion, wire corrosion, etc.
Basically, you can test the sensor by measuring voltage or resistance, although voltage usually gives more information and gives that information faster. If the voltage is weird, then you can check the resistance, etc. If not, you can move on to testing the next sensor.
*NOTE*: I did make a slight simplification. TPS sensors, and most 5V based sensors, actually have a signal range of 0.5 to 4.5 VDC so the ECU can detect failure or a disconnected sensor if the range is outside of that. The sensor readings in the manual already reflect that.
Last edited by Fabrik8; 10-14-2008 at 04:13 PM.
10-14-2008, 06:22 PM
#13
NEO VVL N1 BITCHES
Join Date: Aug 2003
Posts: 2,877
Likes: 0
Received 0 Likes
on
0 Posts
Re: Nissan/SR20 gurus......please help.
im going to agree that its most likely a MAF sensor. i have one you can try but its in richmond. and i get a constant knock sensor code on my pretty fresh sr20ve, but am having no knock sensor issues. could have something to do with my ecu though.
11-10-2008, 07:33 AM
#17
Snoochie boochies
Thread Starter
Join Date: Mar 2003
Location: VA Beach
Posts: 809
Likes: 0
Received 0 Likes
on
0 Posts
Re: Nissan/SR20 gurus......please help.
Just an update for anyone curious.
MAF sensor was bad. I swapped in a good one and the car runs flawlessly, better than it did before I had these problems. Hauls ass, I didn't know it was supposed to run this well
MAF sensor was bad. I swapped in a good one and the car runs flawlessly, better than it did before I had these problems. Hauls ass, I didn't know it was supposed to run this well
Thread
Thread Starter
Forum
Replies
Last Post