How do I diagnose a malfunction when the annual car vehicle inspection failed?

Question

Help!

My 2001 Mitsubishi Galant 6 cylinder failed the yearly inspection.

The only thing printed out on the report from the garage was a "fail" was an OBD-II test result indicating "MIL Commanded-On." I I don't know what that means.

Also, the yellow warning light on the dashboard has been on (seek engine help soon), and my own OBD-II show a code of P0135 (Oxygen Sensor Heater Circuit Malfunction).

Is the "MIL Command-On" and the P0135 code related?

Is this an easy repair to replace the Oxygen Sensor.

With a little direction, I can fix most anything.

Thank you

Answer 1

It is your oxygen sensors that are malfuctioning. On most vehicles it is as easy as replacing spark plugs. I believe that your vehicle has two oxygen sensors on it. One is located on your exhaust system directly after the manifold, and the other is located on your exhaust system directly after the catalytic converter. All you need is the right wrench and the right O2 sensors, and the job may take you 20-30 minutes. Replacing your oxygen sensors will most likely turn your 'check engine' light off, but if it doesn't, then you may need to unplug your battery and plug it back in after thirty seconds so that your cars computer system can register that it has new O2 sensors.

Answer 2

Emissions Failure 101------

if the MIL (Malfunction Indicator Lamp) is on, the computer has detected a failure or fault in a circuit or system monitored by the PCM (powertrain Control Module). When it is illuminated, the PCM generates a code to communicate to the tech the location of the fault, and sometimes what kind of fault.
The P0135 "O2 heater circuit malfunction, bank 1 sensor 1" indicates that that the PCM sees current and voltage conditions outside expected values, and wants it corrected.
Chances are that the heater in the oxygen sensor on bank 1 has failed. But it COULD also be a failure in the wiring or the connectors. It is important to know what the failure is, because if you just replace the sensor (not cheap) and the code comes back, you haven't repaired anything, and you are already out money that wasn't well spent.
If you are going to replace the sensor, the car has three of them. Two are in the exhaust stream before the Catalytic converter, and one is "downstream" behind the Cat.
It is wise to replace BOTH front sensors together for a variety of technical reasons.
AFTER the repair, the light must be extinguished, as it won't go off by itself.
After the code is cleared, the light will go off, and your car will have to be driven in a prescribed manner for the PCM to actually monitor the systems.
The OBD II Drive Cycle is a procedure prescribed by the Federal Government to allow the monitors to be "set" in the shortest practical time.

Go Here------>

http://www.obd-codes.com/trouble_codes/gm/gm-obd-driving-cycle.php

...to understand the drive cycle. Remember, it must be started COLD. The PCM must see a rise in the coolant temperature of > 60° F for the PCM to begin the tests.
If this procedure is too complex for you or you don't want to spend the time, simply drive the car using all normal driving practices, stop and go, cruise, moderate traffic @ 35 to 45 mph, and some freeway speed with cruise control for 7 - 10 minutes at least a couple of times.
If you do not allow the monitors to set after the light is cleared, and you take it back for a re-test, it will fail again because the PCM can't tell if there are failures in the systems monitored. It will tell the Smog Tech that the monitors have not set, and this is a defacto failure.

Good Luck

Answer 3

code could cause it to run rich and fail -believe code is a 02 sensor malfuntion they are as simple to change as unplugging unscrewing and screwing back in and plugging back in just make sure you have only one some vehicles have up to 6--make sure and anti seize the threads.