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Neon OBDII codes

bruiser's Avatar

Join Date: Dec 2003
Posts: 125

03-18-04, 01:26 PM   #1  
Neon OBDII codes

My son's '97 Neon, with the SOHC engine check engine light came on. I put the scan tool on it, and pulled codes P0135, P0401, and P0403. The last two have to do with the EGR system, and the P0135 is a heater circuit problem with the pre-cat O2 sensor. I suspect the EGR valve needs replacing, or the system needs cleaning. I was watching the O2 sensors, and the voltage was fluctuating as it usually does. What do I look for to clear up the O2 code? Replacement, or is it something else. I've heard on some cars a dirty MAF can cause the O2 code to be set.

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davo's Avatar

Join Date: Apr 2002
Posts: 2,417

03-18-04, 02:12 PM   #2  
A dirty MAF sensor will not set an O2 sensor heater circuit code.The 2 most likely causes are a blown O2 sensor fuse or a faulty O2 sensor.You could have a wiring or PCM problem also.The Egr codes are for low flow(p0401)and electrical malfunction(p0403)you could have a clogged egr port causing 401,403 may be the valve or wiring.Yo need to do some testing to determine the cause.

mike from nj's Avatar
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03-19-04, 12:06 AM   #3  
mike from nj
also, there's no MAF sensor on this car.

you can ohm the heater circuit in the sensor, and compare it to the post-cat one. that'll get you started in that direction.

make sure no wires are laying on the egr tube, where it goes from the valve to the intake manifold, make sure it's plugged in. without a scan tool, it might be hard to pinpoint this one. apply vacuum to the valve(to the diaphram, not the bottom port) and see if the car stalls, all the solenoid does is prevent egr when it isn't desired, so without it working----you would always have egr enabled. maybe ohm that one too, see if it's under say 40 ohms(guessing, i've never ohmed one, the book test doesn't do that)

let us know where you get

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