98 240sx ka24de absolute pressure sensor

[s14280zx]

A while ago my check engine light came on, and I tested it and the code was p0105 (absolute pressure sensor). It never gave me any problem until the other day. I was coming down a steep hill and let off the throttle slightly, and it started cutting out. My 1st thought was I haven't changed the fuel filter for a while, and since the weather suddenly got warmer, I filled the tank and put injector cleaner in, ran it back down to quarter tank, then changed the fuel filter. I thought it might of had water in the gas. Took it for a ride, and went on a bumpy lake road, let off and it started cutting out again. It drove fine on the flat highway on the way home. When I got home I opened the hood , unplugged the aps, and the other one on the firewall(map baro solenoid valve, and then pulled the vacuum line off that goes from engine to the aps on the sensor side, and plugged the line, took it for a ride, and it had no miss, and had noticeably more power. My question is will running it without this sensor hurt anything?? I plan on replacing it, but I have to wait a few weeks, and don't want to make things worse. Any help would be appreciated. THANKS

[centralcoaster33]

Get FSM for diagnoses instructions. IIRC the MAP/BARO is one sensor and one switch. The switch changes the source of vacuum from manifold to atmosphere. The sensor merely senses that pressure and tells the CPU. Check hoses for leaks. Pull the switch and run current through it to see if the plunger moves (might need canned air then lube to clean it up if gummed). All that is pretty much free so you can start tonight even. If you have a way to apply pressure with a pump tool, you can test the sensor resistance with the voltameter.

If it were my car, I'd do the above in an evening. If it seems like I needed a part I couldn't afford for a while, but the car seems to be working while unplugged, I'd still drive it. I figure it's in a limp mode, taking guesses at air based on TPS and MAF. Absolutely do not push the car. Just cruise to work/ school and back home. Walk or carpool when possible.

It sounds like you have the things unplugged by wires and a hose, but I can't tell. I don't think the aps is connected to the engine as you mention. I believe it is connected to the switch, but I'm merely using my memory, which isn't that great.

Perhaps a tech or expert will offer more reliable input.

[s14280zx]

Yep, you're right, I unplugged both electrical plugs, and the vacuum line that comes from the engine to the one closer to the firewall which has three vacuum hose connections. I pulled the vac line off of the switch, and plugged it so it doesn't leak vacuum. So far, It hasn't skipped a beat. I found how to check the switch, but I need to buy a pump to check the sensor. Thanks For the help. I'll be fixing it soon as the weather breaks.Until then, I'll have to settle for my Xterra.

[s14280zx]

My miss was still there, only after I drove for a while, then I stopped to eat, then when I went to town in stop and go traffic, it started missing again . I tested the switch with 12v. and it works properly. I need to buy a vacuum pump to test the sensor tomarrow. With the sensor and switch disconnected, you can tell it's in open loop mode because it's running rich and gets worse gas mileage.

[s14280zx]

UPDATE: I ordered a map sensor from Autozone that's supposed to be exact fit for '98 240sx. Got it today, and it's not the same as the old one. It did plug in, but the vacuum outlet points in the wrong direction and is bigger. Before I returned it, I tried it, erased the code with my GST, shut it off, and when I start up, the check engine light comes back on after about 5 seconds. Same 0105 code comes up. I tested the switch by connecting to the battery and it's ok. Could the tps or front/rear o2 sensor cause this code, and what else could this be? It only misses after I drive for about an hour or so, shut it off for a couple minutes, then start driving again, and it seems to start cutting out when I let off the gas. Could someone please help me figure this out? Any suggestions will be appreciated. I'm running out of hair to pull out.

[s14280zx]

Put everything back together today. Took it for a small ride to warm it up. Erased the codes with my gst. Started up again, 5 sec, cel came on again. This time two codes came up: p0105, and p1105. Please help!

[zachattack_5491]

Have you checked vacuum? Make sure those hoses aren't leaking.

[s14280zx]

Yep, my vac hoses are still in good shape and are connected tight. I'm trying to figure out what else can cause these codes to come up. I'm thinking o2 sensors, throttle position sensor, or maybe coolant temp sensor .? It has about the same symptoms as a bad o2 sensor, being that it only does it when it's been running for over an hour. I was also wondering if the iiacv has anything to do with it. Could someone please share some knowledge with me? Any other ideas of what it could be.

[zachattack_5491]

Did you go through the FSM guide for the code diagnoses? I was going to copy pasta it, but it's a little more than I expected. I think that will help you narrow it down to bad components or electrical issues. Being OBDII, I don't think those other sensors would affect it without getting a code. The sensors that kind of bounce information off one another are the map/baro, maf, egr, and tps.

Edit: I would suspect that part that isn't an exact fit. Try figuring out what the deal is with that first off. Also, it does make sense that you get a little stumble on decel. The main reasons they added a MAP to the KA is to check for rationality of the MAF, testing the EGR, and to reduce emissions on decel. It senses the deceleration and attempts to cut fuel when it's not necessary to keep the engine running.

[s14280zx]

That's what I was thinking too, that those sensors would trigger their own code. I'll have to dig further into my fsm, and test the boost sensor. I did test the switch by hooking a battery to it, and it opened and closed properly. I took it for a 100+ mile ride today. After about 60 miles, I shut it off once, left it sit 10 minutes, it ran fine. On the way home I drove about 30 more miles, got some drive thru pizza, went to a nearby lake 3 miles away, shut it off to eat, took 10-15 minutes tops. Started it again, drove 2 miles to a redlight, went to pull out slowly accelerating, and boom started bucking and hesitating,and surging when trying to accelerate, I had to feather gas to keep it running. I turned around and went back to the lake, missing the whole time until I parked in neutral with it idling. It had a slight miss at idle, but it reved fine with no miss from under the hood. I shut it off, let it set 15 minutes, started it back up, and drove 30 miles home with no misses. Thanks for the help. Any other ideas? Loose speed/ gear sensors?

[s14280zx]

I tested the map sensor and harness today following the fsm step by step. All three wires checked ok. Turned ignition on(not running), checked for voltage at ecu terminal 66 (supposed to be 3.2-4.8v), No voltage. Pumped 7.87 inHg vacuum to sensor, still no voltage. Guess I need a new sensor. Today I drove it about 30 miles, then parked in a parking lot letting it idle. It ran for an hour total. Didn't shut it off this time, drove for 1 to 2 minutes, bogged badly on accelleration , i'd pull off the road, push the clutch in, and it revved fine, go to take off again, bogged again, did it whole way home. It does it while under load, but not while idling or revving while sitting still. It does it on acceleration, and sometimes while letting off slightly. Does this sound like map sensor symptoms? Would the fuel pump do this? Please help!

[s14280zx]

UPDATE: Today I got my used map sensor from ebay($25.00 ). Put it in, checked for codes, no codes . Took it out tested it, got alot better gas mileage, stopped and shut it off for 15 minutes. When I started it up, I could tell it was missing right away. Once I revved it up a few times It smoothed out. Got home and checked sparkplugs, ok, took dist. cap off, all 4 contacts were corroded, and the rotor contact was actually rusty. Took the cap and rotor off my '95 240sx and swapped them. Took it for anothr test run, ran great I LEARNED TWO THINGS FROM THIS AND MY PAST EXPERIENCES: #1: WHEN YOUR CHECK ENGINE LIGHT COMES ON, WHATEVER CODE IT IS, IT IS RIGHT, THE ECU DOESN'T LIE. #2 DON'T NEGLECT TO CHECK THE SIMPLEST TUNE UP ITEMS BEFORE CHECKING ANYTHING ELSE. THANK YOU TO ALL WHO TRIED TO HELP ME, SEEMS LIKE LATELY NOT MANY TECHNICIANS HERE ARE WILLING TO HELP ANYMORE. HOPE THIS HELPS SOMEONE ELSE WHO MAY RUN INTO THE SAME PROBLEMS AS I DID.

[alms24sebring]

Yeah I had the same issue. My MAP sensor went bad but I could never find it or get the right one because it was called a boost sensor (which obviously makes no sense since its vacuum). It was so stupid and make me look like a retard, but it wasnt my fault. Its crazy how and when cars decide to act up.

[s14280zx]

Yeah, I've owned my 98 240 since 2001, and I've had quite a few sensors go out. O2 sensor, crankshaft position, maf, and now the map. Each time the ecu code was right. One year, I bought new nissan caps and rotors for both of my 240's, and I was thinking it was more recently, so I didn't think to check it.

[s14280zx]

Thought I had it fixed, ordered a new cap and rotor from courtesy nissan, put it on today, took it for a run, same problem again, cel back on again Got it home hooked up my gst, two codes came up, but it couldn't read the codes. Broke out my fsm book, took me awhile, but I figured out how to read the codes off of the ecu. Came up maf & knock sensors. Took the maf off my '95 240 (my poor zenki ) put it on, took another good look over everything, and found something else! I've had an Injen short ram on since I first bought my '98 240. A while back, the plastic T that connects the pcv to the air intake cracked, so I put one of those cheap breather filters on the pcv. Since the pcv tube is so close to the valve cover, the rubber hose for the filter had to be bent tightly which stretched the hose for too long. Well, underneath where you couldn't see, the rubber hose was cracked and dryrotted clean through. I got a new filter, but this time I got a 90* pcv elbow(for ford) and a straight barb fitting to connect elbow to filter. It turned out good. Cleared the codes off, took it for a run, shut it off several times, kept trying to get it to miss, no misses, no codes, and it even idles perfect now. I suspected the knock sensor code was triggered by the severe hesitation and bucking when it was missing.I'm glad 'cause that looks like a real b**** to change. Hopefully this fixes this once and for all.

[Thornurn]

I need big time help i have gone through so many forums and videos trying to find this out. WHERE IS THE MAP SENSOR LOCATED. I have looked everywhere please help

[VStar650CL]

IIRC, on a KA it should be on the passenger side behind the battery, it's mounted on a little cad-plated bracket with the vacuum hose coming out the bottom. See EC-12 here, the drawing isn't great but follow the vacuum hoses from the manifold and you'll find both the sensor and the solenoid:
https://www.nicoclub.com/service-manual ... 6%2Fec.pdf

[Thornurn]

There is nothing there for me i habe looked everywhere and some say the isnt supposesd to be one