This code deals with your evaporative system circuit which controls emission created by escaping fuel vapor in your gas tank. This circuit consists of all the vacuum hoses between the tank and all components used to catch the gas vapor like the canister container used to store gas vapor, solenoids and valves which are used to open/shut the flow of gas vapor between the canister and throttle body, the computer which control all of these components and finally the wirings between all these parts.

This code will start flashing in your dash panel when the gas cap is not properly installed, one of the solenoids failed to work or the canister itself is defective or a failure in other components like leaky vacuum hoses, bad gas after you changed gas station or defective computer module.

To fix this problem, always check the gas cap first because it accounts to almost 80% of the problem. If the vehicle has a lot of mileage, you are better off replacing the gas cap. Should the code persists, get hold of a vacuum diagram so you can trace and check all the affected components. Further more, look for the obvious common problem like signs of gas leak which can be seen visually.

Tip:

Any wetness seen on the sides of the canister means a gas leak which needs a closer attention. The same can be said about leaky vacuum hoses and solenoids. Worse comes to worse, always follow the wiring diagram circuits to make sure all the components and solenoids are properly grounded at the right time.

Have fun!

P0420 code denotes a malfunction in the catalytic converter (cat) as designated by the post (downstream) oxygen sensor. As in many cases like this, it is a good idea to measure the voltage oscillation of the oxygen sensors between the front and the back oxygen sensors. At the front (usually located at the exhaust manifold), it should oscillate about 0.1 to 0.9 volt at
the signal wire whereas the back ones should oscillate less say around 0.3 volt to 0.6 volt. Depending on the models, if the oscillation is greater than this, it indicates a CAT failure.

Tips:

Most cat is guaranteed up to 8 years or 80,000 km so check with your dealer and service bulletins if your vehicle is covered.

If your vehicle is not covered, you can buy an after market cat with at least 50% savings but make sure it follows the manufacturer’s efficiency guidelines. To confirm this, get an exhaust analysis reading before and after the catalytic converter is installed.

On some imported models, there could be no voltage oscillations at the post oxygen sensors, to be safe contact ATS for the right readings.

Make sure the engine computer (ecm) is fully cleared of the code after installing the new cat. If not, the P0420 code can return and give you a false code.

Thanks!

This code means a lean fuel mixture condition detected by too much presence of oxygen in your exhaust. This is monitored by your oxygen sensor mounted in your exhaust manifold. This is also similar to P0174 fault code. This fault code can be caused by dirty mass sensor wiring element contaminated by the presence of oil in your air filter. Cleaning the mass sensor element and replacing the air filter will fix this problem. If the fuel filter has not been changed for a while, now is the time to do it.

To verify this code, make sure you have the following symptoms before doing anything:
Hesitation, lack of power, detonation and sometimes surging. If after doing the repairs suggested above, the code remains, try these:

NOTE: It is understood that the engine has been checked for vacuum leak before doing these repairs. Also, check vacuum hoses for cracks and vacuum reading if possible. For assistance, contact ATS.

On some occasion, if you have a mass sensor code and you try to service the mass sensor, the fault code could be fixed and the engine light could go away. What happen if the servicing does not work? Here is a quick way you can check it using your DVOM voltage meter:

Using a wiring diagram, determine the signal wire of the mass sensor. Example, if you have 4-5 wires on the sensor, one of them will be a signal wire. So how do you find it without a wiring diagram? Well…if you measure each of the wire, one of them will change voltage reading if you rev up the engine speed from idle to high idle. If one of them changes, that is the one. If none of them changes, then the sensor is at fault. Of course if you have the diagram, you can pinpoint the signal wire right away and trace the wiring up to the ecm pin terminal for continuity. For more details, contact ATS.

Thanks!

A lot of times when you scanned an intermittent oxygen sensor fault code, you will be stumped because after you changed the oxygen sensor, the code still remains. Then you give up and surrender the troubleshooting problem to a garage. This is of course will cause you more expenses and waste of your time. However, a quick check on your oxygen sensor heater wiring circuit might help you get over this nagging problem.

You see, most newer type of oxygen sensor has extra 2 wires intended for the heater element built in inside the sensor. This heater helps in getting your sensor works better by heating the sensor quickly including improved monitoring of the sensor signal wire function. Unfortunately, there is a downside on this because you have extra wires dangling around and if this heater wire insulation is shorted, the heater circuit can fail and also affect your engine computer.

As a precaution, if you have a repetitive intermittent oxygen sensor code, make sure to open up your heater wire harness and look for signs of rubbing, wire discoloration especially on wiring harness routing that are close to exhaust manifolds or metal contacts usually at the back of the cylinder head. You can also check the continuity of the heater wires from the sensor up to the engine computer terminal pins by using a wiring diagram. If you are lucky, you might find the shorted oxygen sensor heater wire that is causing you the oxygen sensor intermittent problem. If you need a wiring diagram for your oxygen sensor heater wires, please contact ATS.

Good luck!

This P0201 code means cylinder injection circuit malfunction and it may look formidable but if you have a troubleshooting diagnostic tree, it should be easy for you. Shown is a sample diagnostic tree below that you can see. All the confusing terms here are available at ATS as shown below the diagnostic tree.

Here are the basics test available to you:

basic vacuum leaks testing
basic exhaust manifold exhaust test procedures
testing exhaust manifold vacuum pressures for catalytic converter
testing oxygen sensors using your DVOM
EVAP system checking canister purge solenoids
testing injectors for resistance and spray patterns
testing fuel pressure regulator vacuum pressure and common problems

For your safety and guidance so you can do it, be sure to register at ATS.

Thanks!

If your dash is flashing a service light and has a TPS sensor fault code, try these:

Find out the signal wire of the tps sensor using a wiring diagram. On older vehicles, tps sensor has a 3 wire connections namely the reference wire , ground wire and signal wires. When testing the signal wire, turn your key on with engine off and measure the voltage on 2 positions of the throttle linkage. First on idle and 2nd on WOT position by moving the throttle linkage to full gas position (high idle). The voltage reading on idle should be around 0.1 v and max at WOT (high idle) between 0.8 v-0.9 v. While moving the throttle linkage, there should be a gradual increase of voltage between these positions. If not, it is called a glitch and will make the tps sensor defective.

NOTES:

1.) Both reference and ground voltage readings stays at 5.0 v and at zero (0) v respectively. If not the tps sensor is also defective.

2.) On new vehicles, the tps system is replaced by a tps control actuator by the throttle body and a tps switch at the gas pedal. The signal wire is still present and can be tested if you have a wiring diagram. For assistance, contact ATS.

Thanks!

Whenever you get an oxygen sensor code such as P0172 or P0174 codes, reset if first by disconnecting the battery terminal (-) connection for 1 minute and reconnect. This way you can road test it and verify the code itself if it is a temporary or permanent code. In the case of the latter, here are some simple steps to check the oxygen sensors:

Get hold of the wiring diagram of the oxygen sensor so you can locate the oxygen sensor wire colors and location (you can buy this from your local parts store or from the Internet). Once you have seen the oxygen sensor/wirings, make sure to check the wires for integrity for insulation and routing. Oxygen sensors are usually located in exhaust manifolds and if the wires are too close to the manifolds, it could get burnt and shorted. If the sensor has a heater circuit, make sure that they are properly grounded by checking the continuity from the sensor to the computer pin terminals.

Oxygen sensors are used to monitor the status of engine fuel mixture and catalytic converter. The former are located upstream in the exhaust manifolds whereas the latter are located downstream after the catalytic converter. When testing these sensors, take note that the voltage readings will be slightly different but as long as the voltage fluctuates after warmed up (close loop) between 0.1 volt to 0.9 volt, the sensors are OK (the fuel mixture can be enriched or leaned during the sensor voltage testing by manually adding fuel like propane to the intake vacuum openings). Finally, like any other engine parts, oxygen sensors get worn and are supposed to be replaced between certain intervals. Check your vehicle service manuals for the maintenance procedures.

For detailed instruction on how to repair an oxygen sensor code for any model of vehicle up to 2005 including the supply of a wiring diagram, please contact ATS.

Thanks!

Do you realize that if you have a faulty oxygen sensor, your gas mileage will be screwed? Think again, oxygen sensor is like your gas mixture adjustment in your old carburetor system so that if it is not set up properly, the mixture will either rich or lean. Meaning, bad gas consumption whereas oxygen sensor automatically set this up for you.

Oxygen sensor is one of the most neglected part of your engine because almost nobody really understand on how it really affect your pocket book. Besides controlling your gas mixture, you will notice that when you go to a garage and complaining about failed emission smog test, oxygen sensor is the one they will always recommend for replacement.

Whether oxygen sensor fault code is flashed in your dash or not, oxygen sensor must be replaced regularly depending on the type of vehicle you have. The older it is, the more frequent it should be done because newer oxygen sensors has been upgraded to last longer. You might replace the oxygen sensor at 50k-60k intervals for models between 80s to early 90s engines and around 100k for engines after late 90s. If your oxygen sensor is not showing in your dash, here are common symptoms when they start to fail: reduced fuel economy, pungent smell in your tailpipe, no start if your catalytic converter is failed already, hesitation, cutting out and failure to pass emission test.

Can you change your oxygen sensor yourself? Of course you can if you know what to look for. ATS can give you the exact location of the oxygen sensor including the proper servicing of the wires and maintenance so it is in top shape condition. Tomorrow, I will give you some tips on how to test the oxygen sensors.

If after you serviced the mass sensor, it does not work then what’s up?

Servicing the mass sensor is widely discussed in ATS and you can even see the ATS video on how it is done. However, sometimes it is not enough and you still have to check the mass sensor wires. Also, make sure the air filter is clean because this is normally the cause of a faulty mass sensor.

How to test the mass sensor wires? Try this below:

Mass sensor is usually located in the air filter ducting to measure your engine air volume flow. All you do is find the mass sensor signal wire going to the mass sensor harness connected to the mass sensor. Using a DVOM (digital voltage ohm meter), monitor the voltage at idle and do the same at high idle. There must be an increase in voltage until it taper off when you hold it at certain high rpm (I would use 2500 rpm). If the measurement does not show this, replace the mass sensor.

Note: You can also locate the wiring colors of the mass sensor if you have a wiring diagram to use (of course it will be given to you if you are a member of ATS). Remember to erase the code and take it for a road test after replacing the mass sensor.

Thanks!