This P0320 code means the crank sensor circuit is malfunctioning. However, on most Chrysler product such as these Jeep models, this crank sensor fault code is actually a misnomer because the problem points to a camshaft sensor problem. Symptoms of this code are no start, stalling and the check engine light coming on. Another feature of this P0320 code problem is the ignition coil starts to overheat which will later cracked. Even if you replaced the ignition coil, they will overheat again after a few hours of operation. It is also noted that the ASD relay will start clicking as soon as this code is displayed in your dash.

When testing, start by checking the crank sensor wirings integrity like short and open connections between the sensor and engine computer. Then do the same on the camshaft sensor which is the normal culprit of this problem. To be sure, you can have a garage monitor the camshaft sensor wirings using labscope method ( a detailed way of graphing the wiring voltage in milliseconds) but the price you will pay for this service might be cheaper if you put a new camshaft sensor yourself.

Tip:

To locate the crank and cam sensor, it is a good idea to get a wiring diagram and installation procedure because this might a need special tool to do the job.

So remember not to rush in replacing the crank sensor yet when you see this P0320 code if you work on Chrysler vehicles like Jeep. This can save a lot of aggravation since you will avoid replacing unnecessary parts. Finally, make sure to reset the code after you replaced the cam sensor.

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This P0422 code refers to catalytic converter (cat) below the threshold rating or to make it short, is inefficient which means the cat is worn. Common symptoms for Hyundai vehicles are hesitation, pinging, cutting off and sometimes lost of power. The quickest way to test this is to check the mass sensor which can be either serviced and re-tested and look for signs of improvement or disconnecting the mass sensor and see if there is an improvement in the performance.

If the above quick tests do not work, you can do inspections like measuring the vacuum reading at 2500 rpm and see that if the reading suddenly drop to zero and stay there. Normally, it should drop slightly but it should go up 2-3 inches using a vacuum gage. Another method to use is to measure the voltage signal of the oxygen sensor after the cat. This sensor monitors the cat performance and if there is an issue with the cat, the voltage reading will oscillate wildly instead with of a small oscillation.

Another way to test this P0422 code on Hyundai vehicle is to take out the oxygen sensor at the affected exhaust manifold located near the engine cylinder head. When removed, it will make your cat breathe and it can be verified by road test. If the performance suddenly improves, it shows the cat is really plugged. If you are up to it, you can also raise the back end of the vehicle so you can go underneath the vehicle and tap the cat with a rubber mallet. A defective cat will show loose stuff inside which shows the cat content is already deteriorated.

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P0300 code stands for random misfiring of engine cylinder combustion. If misfiring is present only on specific cylinder, the last digit usually indicates the faulty cylinder causing the misfire. Example, if the code is P0301 it means cylinder one is misfiring whereas P0304 code refers to cylinder number 4 that is misfiring. Some of the symptoms of P0300 code are rough idle, hesitation, cutting off and other related problems associated with misfiring.

P0300 code is caused by failure in the ignition system like defective spark plugs/wires, bad ignition coil or coil plugs and even a faulty ignition module. Engine electronic component failures are common on this code like defective crank or camshaft sensor, bad oxygen sensor and the engine computer. Mechanical components can fail also causing this code such as bad engine compression, internal wear, vacuum leak, faulty injectors and defects in the exhaust system like the catalytic converter and EGR valve.

One of the quickest way to check this P0300 code is to reset the code and see if the same code repeats itself. If it does, do a visual checks on the engine compartment for possible vacuum leak like a leaky vacuum hose and testing the operation of the EGR valve pintle rod. Next make sure all the parts for the engine tune up is updated. This is important especially if such filters like the air and fuel filter has not been changed lately. This code is actually solved on a common problem and once it is found, it will be fixed. Unlike code P0301, this specific cylinder misfiring is normally fixed by swapping parts which are working. Example, if you have a code P0301, you can switch the injector of cylinder 1 to cylinder 3 and if the code changes to P0303, then it means the problem lies in the defective injector.

Tip:

Ignition coil pack, spark plug wires, coil plugs can be swapped too by switching a suspected part with a good part that is proven to work. If the symptoms followed the suspected part, then the suspicion is verified such as the P0301 code example above.

P0125 will set if the engine coolant temperature cannot be reached at a specified time. Most of the time, it detects if the engine coolant thermostat is defective or not. Other causes of this faulty code are bad coolant sensor, inoperative radiator cooling fan, defective thermostat. To make sure this code is being set, reset the code by disconnecting your battery for 1 minute and reconnect. Take the vehicle for a road test and if the code returns, it shows the coolant code is serious.

Basic testing of P0125 code requires verifying the coolant level and touching by hand the thermostat housing for any signs of temperature change (be careful). The coolant sensor wirings can be checked visually and sometimes disconnected to see if it is getting contact from the engine computer. A wiring diagram can be used to check more complicated wiring issues but getting the assistance of an online mechanic can give you a faster result.

Fixing this P0125 code depends on your findings shown above after check ups. Here are other common fixes suggested by ATS. Verify the voltage readings of the coolant sensor as suggested by the engine specifications. Do the same on the air temperature sensor whenever the sensor is used. On some throttle sensor (tps) circuit, the coolant sensor has a common ground shared with the tps sensor. If the tps sensor wirings are shorted, it will also affect the coolant sensor. Again make sure to use a wiring diagram because not all engines have the same set up.

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Oxygen sensors are hooked up in the engine exhaust system in 2 locations; at the exhaust manifold and after the catalytic converter (CAT). In the first location, it is use to give signal to the engine computer so it can control engine fuel mixture. This is done by monitoring the amount of oxygen present in the exhaust gases by monitoring the equivalent voltage generated. When in operation, there is little time required to make the oxygen sensor work since the sensor’s probe requires some heating up. When that set temperature is attained, the oxygen sensor begins to work and it is called “close loop” cycle. That cycle is the time when the voltage signal of the oxygen sensor began switching between 0.1v to 0.9v. This signal reading is used by the engine computer to control the fuel trim of the fuel mixture.

So how does P0135 code come into effect? To shortened the time to reach close loop, a heater element is added to the oxygen sensor circuit. This heating element is also being monitored by the engine ecm so that if the time required to reach the close loop started to get longer, it will set a code P0135. Most of the symptoms for this code is poor fuel economy since the engine computer will have difficult time controlling the desired fuel trim. To check this code needs testing the heater element wires for continuity, open, short and resistance.

Tips to repair P0135 code:

When checking for the voltage reading of the oxygen sensor heating element, always use the wiring diagram for the appropriate oxygen sensor circuit.

Follow the manufacturer recommendation as to when to replace the oxygen sensor because the switching voltage reading will slow down when the sensor has accumulated too many miles of operation.

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P0174 code means the fuel mixture is lean as indicated by the presence of too much oxygen. This code also is similar to P0171 except it occurs in bank 2 opposite bank 1 for the former code. The common symptoms are lack of power, occasional pinging or detonation, maybe the engine running a little bit hot accompanied by hesitation or even surging.

The most common fix is almost always to service your mass air flow sensor. As mention earlier, the mass sensor has a wiring elements which monitors the air flow volume. This same element can be easily corrupted if the air filter is dirty especially the oil soaked type wet type air filter which can be overfilled and saturate the wiring element. If the air filter is not service regularly, dirt could cover the wiring element with unwanted debris.

Tip:

After cleaning the mass air flow sensor and taken the vehicle for a road test, take note if there is a slight change in the engine performance. Also, if after driving it for a while and the code returns (only this time, it took longer to come out), don’t even think about it….replace the mass air flow sensor.

It is always important to mention here to check the basics for lean fuel condition which is caused mainly by a vacuum leak. This requires checking the air filter ducting for cracks or loose mounting that would cause the vacuum leak. Include testing the vacuum hose and the pcv valve which could be defective. As always, if you fix the source of the vacuum leak, this code P0174, along with P0171 will be solved. Otherwise, contact ATS for assistance so a detailed wiring diagram can be sent to you to get a closer inspection of the oxygen and mass sensor circuits.

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Dealing again with your evaporative system which is designed to avoid leakage of gas vapor to the atmosphere, this P0455 code expands this problem further. As you will know, this is accomplish by having a purge solenoid which allows the flow of gas vapor between the tank, fuel canister and throttle body. When this solenoid is defective, the flow could be disrupted and prevent the circulation of gas vapors in the system. Furthermore, the most common problem here is leakage which can occur at the solenoid, canister, vacuum hoses and especially coming from a loose gas tank cap. Such leakage will allow hydro carbon gas like your fuel gas vapor to escape to the atmosphere.

Any leakage in the gas flow will be detected by the computer since it controls the purge solenoid by getting the fuel mixture signal from oxygen sensor. When this happens, this code will be flashed in the vehicle dash panel. To correct, always go to the gas cap first and make sure it has good sealing gasket and installed tight. Next, visually inspect for vacuum leakage by checking for ruptured vacuum hoses, plug pcv valves or cracked canister.

Tip:

Any vacuum leakage can be seen by signs of wetness in the area involved. If a vacuum hose is leaking, the defective area should be wet with gas or even a smell of gas.

Once this vacuum test is exhausted, the best way to find the leak is to have it checked by a smoke machine used by garages to detect miniature gas leak not visible to the human eye.

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P0325 code is a malfunction in the knock sensor which is designed to monitor piston knocking when the engine is running. As a matter of fact, this code can be induced by tapping the side of the engine block with a hammer where the knock sensor is located. This code will come if the engine itself is knocking which could be caused by lean fuel mixture which can occur with detonation on top of the piston. When this happens, the knock sensor will send signal to the computer to slow down the engine ignition timing to prevent further damage to the engine.

Engine detonation can damage the piston and valves of the cylinder head when the detonation is prolong. When this happens, the engine should be stopped and inspection of the knock sensor made. Most of the time, the knocking originates from a defective knock sensor or a faulty wiring connected to the sensor. Once removed, the knock sensor can be measured for resistance and compared to a new one. On other cases, it might be necessary to check the wirings between the knock sensor and the computer pin. If the wirings are proven OK, replacing the knock sensor is usually the common fix otherwise, check with your dealer to have your computer upgraded or re-program.

Accessing the knock sensor is very easy and on most GM engines, the knock sensor is located in the side of the engine block. However, on other types of engine, you might need a wiring diagram so you can identify the color of the wires to the knock sensor. Finally having a wiring diagram or an online mechanic to help you can prevent removal of parts which are not needed.

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EGR stands for exhaust gas recirculating system which is a means to feed exhaust gas to your intake manifold to reduce emission. In the normal set up, an egr system consist of the egr valve which allows the exhaust gas to flow, an actuator solenoid which controls the vacuum going to the egr valve and finally the egr pressure sensor which measures the difference in pressure in the atmosphere and vacuum circuit which also helps the smooth flow of the exhaust gas at the egr valve.

When this code appears, it usually caused by the following reasons:

EGR valve is stuck and the pintle rod won’t allow the flow of gas. When testing, measure the vacuum going on top of egr valve and do it at idle and high idle. The vacuum reading must not be the same otherwise, the egr valve is defective.

EGR solenoids can also fail mechanically but the most common problem is the electrical wirings. It should be checked for voltage and resistance readings and compare it to the standard readings as suggested by the manufacturer.

EGR pressure sensor can fail depending on the make of the vehicle. On fords, this is a common part to fail and can be checked by using the common fixes as suggested by ATS.

TIP on egr system

Having an engine vacuum diagram can help you identify all the egr system components.

When your egr system fails, its like restricting the vacuum going to the engine manifold which could make a rich mixture causing misfiring. On the other hand, if the egr is stuck open, it will make the fuel mixture lean.

The best way to check this code is to check for vacuum leak on all components including the integrity of the vacuum passages and wiring circuits. It also advisable to reset the code and see if the code re-appears so that each of the 3 major parts above are checked individually.

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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.

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