Questioni have had a 02 sensor problem on my car for quite some time but now recently i went to get my car diagnose and 6 sensor problems came up someone told me that i may need an intake manifold but i want to get different opinions. the 6 sensor problems are(1) p0139 which is the 02 sensor(2)p0301 which is the cylinder 1 misfire(3)p0134 which is another 02 sensor circuit no activity(4)p0121 TPS/pedal position sensor(5) another p0121 which says its pending and finally (6)p0106 which is map/baro ckt range sensor..if anyone may be able to help me come to a conclusion on how to better assist myself and maybe know how much this thing may cost , it will be greatly appreciate. Thank you
AnswerHi, Jerry. One of the problems with continuing to drive with the check engine lamp on, as you've discovered, is that you have no way of knowing when a new problem has developed. I'll provide my thoughts on your situation below.
P0139 and P0134 can be caused by a leak in the exhaust manifold or front exhaust pipe. If you have any exhaust leaks, fix those first and clear your diagnostic trouble codes. If P0134 returns, replace the upstream oxygen sensor. If P0139 returns, replace the downstream oxygen sensor.
Misfires most commonly occur due to secondary ignition (plugs, wires, coil) issues, so check there first. You already know you're interested in what's happening on cylinder #1, so you can just examine the components on that cylinder. I often check the wires and coil by removing the wires from the plugs and just resting them back down on the plugs, starting the car, and then lifting each wire off the plug gradually to see whether the spark continues to come out of the bottom of the boot or exits elsewhere. If the spark comes out at the coil, replace the coil. If it comes out between the coil and the wire boot at the coil, replace the coil and wires, and if it comes out of the wire anywhere else other than the hole at the plug end, replace the plug wires. If the wires and coil check okay, try swapping the #1 spark plug to another cylinder. If the plug is the problem, the misfire will move to the other cylinder. Another common problem causing misfires on this engine is a leaking intake manifold gasket. This will typically cause a misfire at idle but otherwise normal engine operation. It can also cause trouble codes indicating a lean condition.
This particular year Elantra is prone to throttle position sensor issues, so just by seeing P0121, I'd recommend replacing the throttle position sensor. While doing this, also check the PCV hose and intake air hose for proper connection and leaks.
P0106 is most frequently caused by a problem with the MAP sensor itself.
Lastly, I'll add that since you've a significant number of trouble codes here, it'd be a good idea to check the wiring going to the MAP sensor, throttle position sensor, and the oxygen sensor to see if rodents have been chewing on them.
