barometric pressure solenoid/MAP sensor circuit fault

[djratlif]

So I have been slowly getting after my Frontier now that the snow is finally gone here in Upstate NY. The truck runs beautifully except once it gets warmed up, and throws a MAP sensor/ Barometric pressure circuit fault code. I have replaced both the MAP sensor and Solenoid, (at a pretty penny I may add) and the code is still there with a serious drop in power when it gets up to temp. With the truck running I can plug in my scanner and see that the MAP sensor is reading the same all the time when I when I look at the live feed data. I am now assuming there must be a break in the wire or something that would cause the sensor to read the same all the time. Is there something else that could be causing the issue or is this a logical place to start? I am horrible with electrical diagnosis and could use any input anyone can add at this point. Oh yeah forgot to mention its a 2000 Frontier KA24DE engine, with a 5-speed trans. I would post this on another forum but I always get better results here, seems to be a way better community here than on other forums I have tried. Thanks again, Derek

[Slartibartfast]

I think you're right on the wiring. Something's wrong with one of the sensor wires, and when the computer warms up and starts listening to the MAP, it realizes something's wrong. I'd start by checking connections. If the plug looks good (no corrosion, wires aren't loose), you'll have to test each wire to figure out which of them is broken or making poor contact. I imagine the easiest way to do this would be to unplug the computer, unplug the MAP sensor, and test (with a multimeter set to resistance) from where the wire hits the MAP plug to where it comes out at the computer plug. The factory service manual should have a pin-out for both plugs, but I imagine you could work it out by matching the color codes on the wires. A busted signal wire (or ground maybe) could be causing the problem.

 

This test procedure is for a different motor, but the procedure should be similar:

 

If it's connected via a vacuum line, probably best to check that for dry rot/cracking, and make sure it's not clogged anywhere. A clogged line could also explain the constant reading. (Even if there's no line, I'd still check the hole for any gunk that might have gotten in.) If you suspect that the issue is in the line, maybe have someone suck on the sensor while you watch the live feed?

 

I don't know the KA24DE or MAP sensors in general, so that's all I've got. I don't think there are many KA24DEs on here (not post '95 anyway) so you might find more firsthand experience elsewhere.

[silverton]

your MAP sensor read out should definitely be changing. Have you done a test on the components to make sure they're actually good? Just because new, doesn't mean functional.

[djratlif]

I checked both sensors while I was sitting at work, and I have replaced all vacuum lines within the past few thousand miles when I did the engine swap. The engine swap is the reason I think I have a wire issue, I figure with all the movement in the engine bay knocked a connection loose or pinched a wire. I guess its time to Ohm out some wires and see if there is a broken one, and check connectors to make sure they are all good.